Miniscrews failure rate in orthodontics: systematic review and meta-analysis

Miniscrews failure rate in orthodontics: systematic review and meta-analysis Abstract Background Miniscrews in orthodontics have been mainly used for anchorage without patient compliance in orthodontic treatment. The literature has reported changing failure rates. Objective The aim of this review was to provide a precise estimation of miniscrew failure rate and the possible risk factors of the mechanically-retained miniscrews. Search method Electronic search in database was undertaken up to July 2017 through the Cochrane Database of Systematic Reviews, MEDLINE, Scopus, and Ovid. Additional searching for on-going and unpublished data, hand search of relevant journals and grey lietraure were also undertaken, authors were contacted, and reference lists screened. Eligibility criteria Randomised controlled trials (RCTs) and prospective cohort studies (PCSs), published in English were obtained, which reported the failure rate of miniscrews, as orthodontic anchorage, with less than 2 mm diameter. Data collection and analysis Blind and induplicate study selection, data extraction, and risk of bias assessment were undertaken in this research. Failure rates and relevant risk factors of miniscrews with the corresponding 95 per cent confidence intervals (CIs) were calculated by using the random-effects model. The heterogeneity across the studies was assessed using the I2 and Chi2 test. The risk of bias was assessed using Cochrane risk of bias and Newcastle-Ottawa Scale. Subgroup and sensitivity analyses were performed in order to test the robustness of the results in meta-analysis. Results The 16 RCTs and 30 PCSs were included in this research. Five studies were not included in the meta-analysis due to a lack of the statistical information needed to compute the effect sizes. About 3250 miniscrews from 41 studies were pooled in a random-effect model. The overall failure rate of miniscrews was 13.5 per cent (95% CI 11.5–15.9). Subgroup analysis showed that miniscrews ‘diameter, length and design, patient age, and jaw of insertion had minimal effect on rate of miniscrews failure while the type of the gingivae and smoking had statistically significant effect. Conclusion Miniscrews have an acceptably low failure rate. The findings should be interpreted with caution due to high-level of heterogeneity and unbalanced groups in the included studies. High quality randomized clinical trial with large sample sizes are required to support the findings of this review. Introduction Orthodontic skeletal anchorage devices are used by orthodontists for a range of clinical applications. These include molar distalization, molar protraction, intrusion of incisors, intrusion of molars, cross bite or scissor bite correction, and anchorage reinforcement (1–7). It was following Konami’s publication in 1997 that orthodontic skeletal anchorage devices, as we know them today, were popularized (8). Orthodontic skeletal anchorage devices can broadly be divided into two categories: osseo-integrated implants such as mid-palatal implants (9) and on-plants (10), and mechanically retained devices such as titanium mini-plates (11, 12), zygomatic wires, and miniscrews (13, 14). The use of miniscrews has increased in orthodontics treatment due to their ease of insertion and removal, reasonable cost, biocompatibility, and capability to withstand orthodontic forces (15, 16). Publications regarding the mechanically retained miniscrews increased dramatically from a few papers in the 1980s to above 5000 papers up until year 2017, indicating a huge interest in skeletal anchorage. Unfortunately, the vast majority of these papers are case reports and biological science research and very few are clinical trials published. Miniscrews should ideally remain stationary when orthodontic force is applied to be effective. The miniscrews stability has become a problem because it does not ground on the osseointegration, but it depends on mechanical locking of threads into the bony tissues and they consequently could hold up the orthodontic loading. Several factors contribute to the success of miniscrews which may be related to the design, related to patient, or related to clinician factors. Age is a factor related to patient with a higher failure rate reported in adolescents as compared to adults as a result of the difference in the buccal plate thickness (17). Poor oral hygiene and smoking are further factors related to patient that reduce the survival rate of miniscrews (18–20). Insertion site and type of the mucosa (keratinized and non-keratinized mucosa) are further patient-related factors. In general, miniscrews have been reported to have a good success rate if inserted in the maxillary region and through keratinized gingivae (17, 19, 21). With regard to miniscrew design factors, it has previously been concluded that miniscrews with a diameter between 1.1 and 1.6 mm provide the best success rate (22). Similarly, miniscrews longer than 5–8 mm are more stable than shorter ones (19, 22). Clinician’s experience, sterilization and asepsis, loading protocol (23), implant placement torque (24, 25), and insertion angle (26) have all been implicated as clinician related factors that may significantly affect the survival of miniscrews. Recent reviews investigated the effectiveness of all types of skeletal anchorage devices in anchorage provision in relation to conventional methods (7, 27, 28). However, the findings of these reviews were not specific to the most commonly used skeletal anchorage device, that is mechanically retained miniscrews. As the determination of specific clinical parameters which influence the clinical success has become critical, aim of this study was to conduct a systematic review and meta-analysis of controlled and uncontrolled prospective clinical trials to amend the actual knowledge about the miniscrews in orthodontic clinical practice, specifically about their stability and their associated risk factors. Methods This review received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. This systematic review was planned and reported accordingly with the preferred reporting items for systematic review and meta-analysis (29) and Cochrane Guidelines for Systematic Reviews (30). This review was registered with International prospective register of systematic reviews (PROSPERO, number CRD42017071441). Criteria for included studies The main research question was defined in PICO format (Table 1). The included studies in this systematic review were human randmosied clinical trials (RCTs) and prospective cohort studies (PCSs) that were published in English till the date July 2017. There was no restriction in the search strategy about the starting date. Since the nature of this study was to aggregate the failure rates of miniscrews, therefore no comparators were needed. Articles on miniscrews with a diameter greater than 2 mm, miniscrews in vitro studies, animal studies, case reports and case series, and review articles were excluded from this research. In cases of unclear study design, the author was contacted twice for further information. If there was no response from the author, the study was excluded. Table 1. PICO format. Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure View Large Table 1. PICO format. Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure View Large Search strategy Controlled vocabulary and free text terms was used to allocate published, ongoing, and unpublished studies. The vocabulary was updated by following the initial search, if necessary, so as to identify all studies to be considered in this review. The following databases were searched until 1st of July 2017 (Supplementary Table 1): MEDLINE via PubMed, Cochrane Database of Systematic Reviews; Scopus and Ovid. Other bibliographic databases were also searched for ongoing and unpublished data including dissertation data, grey literature in Europe, clinical trial registry, ISRCTN registry, dissertation, and theses dissemination as well as Google Scholar until July 2017. A manual search was also carried out in relevant orthodontic journals until July 2017. Reference lists of the included articles and other relevant systematic reviews related to the topic were checked for any additional relevant literature and also to include an additional controlled vocabulary and free text terms if present. The Cohen kappa statistic was used to assess the agreement between the two review authors. Study selection and data extraction Endnote reference manager software was used for removing duplicate studies. Relevant articles were identified first after reading their titles and abstracts. The full text of the potential articles was assessed for eligibility by two reviewers (F.A. and D.B.). With the potential difficulties encountered while translating multiple articles into English, it was decided to only include articles presenting with a full text in English. However, this exclusion criterion was applied following the primary search so as to avoid bias in the search protocol. Two reviewer (F.A., M.A.) blindly and independently extracted study characteristics and outcomes using the customized data extraction form developed by Papadopoulos and his colleagues (7) with the potential disagreements solved by a third reviewer (D.B.). The following information was included for each study: year of publication, setting, study design, number of miniscrews and their characteristics, success criteria, failure rate, and handling of failure. Assessment of risk bias in the included studies RCTs were assessed for risk of bias using the Cochrane collaboration’s tool (30). Each included study was assessed for the risk of bias in 1. random sequence generation; 2. allocation concealment; 3. blinding of outcome assessors; 4. incomplete outcome data; 5. selective reporting; and 6. other sources of bias. Each RCT was assigned an overall risk of bias, for example, low risk if all key domains have low risk, high risk if more than one key domain has high risk and unclear risk if more than one key domain has unclear risk. PCSs were assessed for risk of bias using the Newcastle–Ottawa Scale (NOS)(31). The NOS assesses the studies in the following three domains: 1. selection; 2. comparability; and 3. outcome. In case of disagreement between the two reviewers, a mutual decision through discussion was made. Again, The Cohen kappa statistic was used to assess the agreement between the two review authors with the potential disagreements solved by a third reviewer. Data synthesis and meta-analysis To calculate the failure rate of miniscrews, the original outcome data were pooled in a random-effect model by using the statistical software Comprehensive Meta-Analysis (Biostat Inc., Englewood, New Jersey, USA) and a significance level of 5% was adopted for all analyses. The pooled estimate was computed from studies that reported similar intervention and outcomes. Failures of miniscrew implants were expressed as event rates with their 95 per cent confidence intervals (CI). Taking in consideration the methodological and statistical heterogeneity, a random-effects model was used to assess all pooled estimates (32). The heterogeneity across the studies was assessed using the I2 and Chi2 test for heterogeneity (no heterogeneity = 0%, low = 25–49%, moderate = 50–74%, and high 75–100%) (33). Other analysis Subgroup and stratified analyses were pre-planned and pre-specified (a priori) to explore the effect of miniscrews’ length, diameter, age group, jaw, the study design (RCT or cohort), and sample size (100 TADs and more) pooled estimate. We also planned to explore the effect of the miniscrew design, self-drilling miniscrews, and non-self-drilling miniscrews that require pre-drilling pilot hole before insertion, on the pooled estimate. Subgroup analyses were planned to be used for a minimum of five studies. Assessment of publication bias Publication bias was assessed by visually inspecting the funnel plot asymmetry. Moreover, two statistical methods were used to produce significance tests in order to recognize publication bias: Begg/Mazumdar’s method (34) and Egger’s method (35). Results Study characteristics There were 8636 hits from both electronic and manual searches. After duplicate removal, studies were screened and in the result 7915 studies did not meet the inclusion criteria on the basis of title and abstract (Figure 1). Another 152 of the qualifying studies were excluded after their full texts were retrieved. This was because they were laboratory studies, retrospective studies, systematic reviews, or not relevant to the review topic. The final sample included 46 studies that met the primary inclusion criteria. The included studies were 16 RCTs (36–51) and 30 PCSs (24, 52–80). Among the PCSs there was 1 split mouth study. Five studies, two RCTs and three PCSs were not included in the meta-analysis due to a lack of the statistical information needed to compute the effect sizes (37, 47, 56, 58, 79). However, they were included in the quality assessment of the studies. The authors were contacted twice via email when necessary to obtain more information and, if no reply was received, the study was excluded. Figure 1. View largeDownload slide Flow chart of the selection of studies. Figure 1. View largeDownload slide Flow chart of the selection of studies. The main characteristics of the 46 included studies which collectively included 3466 miniscrews are presented in Table 2. With respect to the setting of study, 36 (78%) of the studies were based purely on university settings, while the other 10 studies took place in either private, hospital, mixed, or unknown settings. Generally, the number of miniscrews used per participant ranged from 1 to 4 miniscrews and the average number per study was approximately 77 miniscrews. Table 2. Characteristics of included studies. Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded PCS, prospective cohort study; RCT, randomised clinical trial. View Large Table 2. Characteristics of included studies. Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded PCS, prospective cohort study; RCT, randomised clinical trial. View Large There was considerable variation between the miniscrews’ manufacturers used in the included studies and in the dimensions of the inserted miniscrews. The diameter of the inserted miniscrews ranged from 1.2 to 2 mm and their length ranged from 5 to 15 mm. As presented, the recorded failure rate of miniscrews in the included studies also ranged from zero to 40.8 per cent. Risk of bias of included studies The random sequence generation domain was assessed as adequate in nine trials of the included RCTs while the remaining trials were assessed as having high risk of bias or unclear risk (Table 3). Allocation concealment domain was graded as having low risk of bias in five trials only and the rest of the studies were assessed as having unclear risk of bias or high risk of bias. The blinding of participants and personnel was not possible in the included trials due to the nature of orthodontic treatment. However, blinding of assessors was possible and was carried out in 6 trials, in the remaining 10 studies either blinding was not performed or the reporting was not adequate. There were no dropouts in the included trials. Therefore, all included trials were assessed as having low risk of bias. Selective bias domain was judged to have a low risk of bias in three trials. The remaining studies were judged to have unclear risk of bias because no information was reported to allow judgment. The summary judgment of risk of bias was assessed to be low in four trials only (36–39). The remaining trials were judged to have overall high risk of bias after all six domains’ assessment was performed (40–51). Table 3. Risk of bias assessment of the included RCTs. Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk CCT, controlled clinical trial; RCT, randomized clinical trial. View Large Table 3. Risk of bias assessment of the included RCTs. Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk CCT, controlled clinical trial; RCT, randomized clinical trial. View Large With regard to the quality assessment of prospective cohort studies, the vast majority of the these studies had mediumquality according to the NOS (24, 52–76) (Table 4). Three studies were judged to have high quality (77–79) and one study was judged to have low quality (80). Table 4. Risk of bias assessment of included cohort studies using Newcastle–Ottawa Scale (NOS). Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High View Large Table 4. Risk of bias assessment of included cohort studies using Newcastle–Ottawa Scale (NOS). Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High View Large Overall miniscrews failure rate (primary outcomes) Out of 46 studies, the primary outcome of this review, i.e. failure rate of miniscrews, was reported in 41 studies. Data of 3250 miniscrews were extracted and pooled in a random-effect model. The pooled failure rate was 13.5 per cent (95% CI 11.5–15.9, P = 0.001, I2 = 57.1%) (Figure 2). Data of 1391 miniscrews were extracted from 30 studies that included less than 100 miniscrews for each study that were pooled in a random-effect model. The failure rate of 12.5 per cent miniscrews (95% CI 9.7–16.1, P < 0.001, I2 = 60.23%) was comparable to the summary points estimates of the effect size of all the studies. Data from the 11 studies where each study included more than 100 miniscrews were then analysed in a random-effect model, the total number of miniscrews placed was 1893. The failure rate of miniscrews was 14.3 per cent (95% CI 11.5–17.7, P = 0.027, I2 = 71.5%). Similarly, in studies where more than 100 miniscrews were placed, the rate did not differ considerably from the estimates of the effect size of the main analysis. Figure 2. View largeDownload slide Forest plot of overall miniscrews failure rate (random-effect model). Figure 2. View largeDownload slide Forest plot of overall miniscrews failure rate (random-effect model). Assessment of the miniscrew failure risk factors (secondary outcomes) Miniscrews diameter and length were reported more in studies than any factor except for the location (maxilla or mandible). Diameter, length, age, jaw of insertion, smoking status, and type of soft tissue were investigated (Supplementary Table 2). Associated factors with miniscrews failure were assessed in planned subgroup analysis when possible. Influence of study design on estimating the failure rate of miniscrews was assessed (Supplementary Figure 1). Fourteen RCTs that included 876 miniscrews were pooled in one random-effect model as a part of the sensitivity analysis. Their failure rate was 13.3 per cent (95% CI 9.7–18, Q = 31.5 P < 0.001, I2 = 55.6%). Interestingly, this was very close to the pooled failure rate (13.5%, 95% CI 11.1–16.4, Q = 76.54, P < 0.001, I2 = 67.34%) of 27 PCSs that included 2374 miniscrews. Influence of length and design of miniscrew on the estimation of failure rate of miniscrews was also assessed (Supplementary Figures 2 and 3). The length of 8 mm was used as a cut-off point to assess the effect of length of miniscrews on the failure rate. The failure rate of the long miniscrews equal or greater than 8 mm was (12.2%, 95% CI 6.7–21.4, Q = 15.2, DF = 5, P < 0.001, I2 = 67.2%) and the failure rate for the short miniscrews was 12.7% (95% CI 10.5–15.4, Q = 47.26, P < 0.001, DF = 26, I2 = 44.9%). Data from 11 studies that used non-self-drill miniscrews and 9 studies that used self-drill miniscrews were pooled. Miniscrews failure rate was 14.9 per cent (95% CI 10.4–20.8, Q = 20.7, DF = 8, P < 0.001, I2 = 88.9%) in the non-self-drill miniscrews group which was not significantly different from the estimate effect in the self-drill miniscrews (14.2%, 95% CI 5.6–31.8, Q = 51.57, P < 0.001, I2 = 71.41%). Only one study (54) evaluated the association between smoking and miniscrews failure rate and it included 110 miniscrews. Seventy-three miniscrews were placed in non-smokers, 18 miniscrews for light smokers (≤10 cigarettes/day), and the rest for heavy smokers (≥10 cigarettes/day). The failure rates were 9.5, 11, and 57.8 per cent respectively. Moreover, one trial (43) reported on the influence of type of gingivae at insertion site. Thirty-two miniscrews were included in the study, those were placed in keratinized tissue (11 miniscrews) showed no failure, 4 out of 21 miniscrews (19%) that were placed in non-keratinized tissue failed. Publication bias analysis Supplementary Figure 4 shows a funnel plot of studies where the effect sizes were plotted against standard error. The vertical line represents the estimate of weighted mean effect size. As one would expect, studies with a smaller sample size and large sampling error would scatter toward the bottom of the funnel plot. If publication bias is not present, the data points would normally expect to be distributed symmetrically around the mean effect size estimate. In this current meta-analysis, the shape of the inverted funnel plot was asymmetrical between the right and the left sides of the plot, which means that there was absence of smaller sized studies towards the right side of the plot. Therefore, a considerable publication bias due to a failure of including studies with small effect sizes seems likely in this meta-analysis. Furthermore, both Begg’s test (Kendall’s tua = −0.34535, P = 0.00131) and Egger’s test (−1.789, 95% CI −2.70 to −0.874, P = 0.00017) suggested that publication bias may be present in this meta-analysis. Discussion This systematic review included 16 randomised clinical trials and 30 prospective cohort studies, in which the miniscrews were used to reinforce orthodontic anchorage. The majority of the included trials were judged as having a high risk of bias. In most of these trials, randomization and allocation concealment procedures were either inadequate or reported incompletely. The quality of most of prospective cohort studies was medium. This can be attributed to the fact that most of included cohort studies did not include a comparison group, thus, they had a lower score in the NOS. The meta-analysis estimated the miniscrews failure rate to be 13.5 per cent (95% CI 11.5–15.9). Sensitivity analysis, after excluding small studies, showed almost similar pooled failure rate of miniscrews (14.3%) to the overall estimate effect indicating adequate robustness of the results. This finding differed slightly from the failure rate that was previously reported by Papageorgiou et al. (7) who reported a failure rate of 13.5 per cent (95% CI 11.5–15.8). The minor difference between the two estimates might have resulted from including additional studies in our meta-analysis (38, 42, 55, 59, 60, 77, 78). Secondly, we excluded retrospective studies, studies with unclear design or studies in language other than English that had been included in the previous meta-analysis (80). Associated factors with miniscrews failure were assessed in subgroup analyses. It appeared from the findings of this meta-analysis that miniscrews with diameter smaller than 1.3 mm had lower failure rate (10.7%, 95% CI 7.6–15) when compared with miniscrews with diameter of 1.4–1.6 mm (13.6%, 95% CI 10.3–17.1) and diameter of 1.7–2 mm (14.4%, 95% CI 8.8–23.5). However, the number of included miniscrews with small diameter was 450 while the included miniscrews with medium diameter were 1586 and the ones with large diameter were 391. This variation in sample size between the included miniscrews and the heterogeneity may have influenced the conclusiveness of the findings. Papageorgiou et al. (7) found comparable failure rates for miniscrews of small and large diameter: 10.9 per cent (95% CI 7.7–15.3) and 14.3 per cent (95% CI 7.4–25.8), respectively. However, they found that miniscrews with medium diameter had failure rate of 12.7 per cent (95% CI 8.1–19.3). Lim and his team conducted two retrospective studies and found that the miniscrew diameter had no significant effect on the success of miniscrew (81,82). Furthermore, the difference between large and medium size diameter was minimum, approximately 0.8 per cent. This was proven in previous study that diameter greater than 1.6 mm seems to confer no significant benefit as wide miniscrews are associated with higher risk of root contact than narrow miniscrews (22). The miniscrews in this meta-analysis were subdivided into short (≤8 mm) and long (>8 mm) group. Most of the studies used short miniscrews (Supplementary Table 2). The failure rate of short miniscrews was 12.7 per cent (95% CI 10.5–15.4) which is slightly larger than the failure rate of long miniscrews (8.3%, 95% CI 3.1–20.2). It is at the discretion of the clinician to consider this difference clinically significant or not, but theoretically, longer miniscrews should have a lower failure rate as they offer better mechanical retention in the bone than shorter miniscrew. Lim et al. (82) found higher failure rate (25%) with miniscrews of 6 mm or less, whereas miniscrews longer than 6mm had lower failure rate (<12%). This could be due to the significant heterogeneities in the subgroup analysis, thus, this finding is not conclusive and it should be interpreted with caution. Furthermore, in this review an arbitrary cut-off point of 8 mm was adopted to assess the effect of length of miniscrew on the failure rate; hence, the possibilities of the overlap of the findings on either side of the cut-off point is high, i.e. those miniscrews with 7.9 mm or less will be included in the short group. It is acknowledged that this cut-off point carries weak specificity on the pooled estimate. The design of the miniscrews was compared in a small number of included studies and did not have any effect on the failure rate according to our findings. The failure rate of self-drilling miniscrews was 14.2 per cent (95% CI 5.6–31.8) and for the non-self-drilling it was 14.9 per cent (95% CI 10.4–20.8). Similar finding was reported by Papageorgiou et al. (7) for the non-self-drilling miniscrews (17.7%, 95% CI 5.1–44.9) but was significantly lower in self-drilling group (7.7%, 95% CI 4.8–12.0). This discrepancy might be due to the fact that we extracted the data of miniscrews design from nine studies compared to three studies in Papageorgiou and team review (7), this might have influenced the estimation of the failure rate. Moreover, this could be due to the significant heterogeneities in the subgroup analysis, thus, this finding is not conclusive and it should be interpreted with caution. Interestingly, Chen et al. (17) in their retrospective study found that self-drilling miniscrews had higher failure rate (33%) when compared with non-self-drilling (10%) (83), though this difference was not significant. Age is a patient-related factor with a higher failure rate in adolescents than adults potentially as a result of the difference in the buccal plate thickness (17). In this review, most studies recruited a mix of young (≤18 years) and adult patients (>18 years). The failure rate of miniscrews placed in young patents was 8.6 per cent (95% CI 4.7–15.1) which is lower than the failure rate reported by Papageorgiou et al. (7) who found that the failure rate in patients younger than 20 years was 12.6 (95% CI 6.4–23.3). The difference between the two estimates was not significant and could be the result of the variation in the included studies between the two meta-analyses. Similarly, the failure rate of miniscrews placed in adults according to our analysis was 11.2 per cent (95% CI 6.6–18.7) compared to 15.5 per cent (95% CI 11.2–21.0) in Papageorgiou and team review (7). In contrary, retrospective studies (82, 84) showed that older patients had higher failure rate probably due to smoking and compromised periodontium. Moreover, these findings may simply be a function of sample size, as there were more miniscrews inserted in younger participants than adults. In our analysis, the failure rate of miniscrews placed in the maxilla was 11.0 per cent (95% CI 8.8–13.7) while the failure rate of those placed in the mandible was 16.5 per cent (95% CI 11.6–22.7). The higher failure rate in the mandible may be caused by the greater bone density, the limited amount of cortical bone around the miniscrews, and the narrow vestibule compared with the maxilla (84). However, it is important to consider the significant degree of heterogeneities in the subgroup analysis during interpretation of the data. Data regarding to the effect of smoking on the failure rate of miniscrews was extracted from only one study (54) in our review and it appears that smoking has a negative effect on miniscrew stability although there is very limited data to support this fact. The type of mucosa insertion and its relationship to the miniscres failure rate was investigated in only one study (43). Chaddad and colleagues found that 11 miniscrews placed in the keratinized tissue had no failures. On the other hand, 1 out of 5 miniscrews would fail when it is inserted through the mobile non-keratinised gingivae. Limitations of the study The overal failure rate of the miniscrews should be read with caution due to the significant heterogeneity (Q = 86.34, P > 0.001, I2 = 57.1%) between the studies. This is to be expected because the included studies had different designs, sample sizes and methods. Inspection of the funnel plot and statistically significant Egger’s test and Begg’s test suggested that publication bias is likely to be present. This bias is expected because the included studies in this meta-analysis and not all of the included trials were meta-analysed because the authors did not report data on failure rate of miniscrew. Additionally, the asymmetry in the funnel plot may have raised because of true methodological and statistical heterogeneity. It is worth noting that the funnel plot is able to indicate the presence of the publication bias but it cannot explain the reasons for the asymmetry (83, 85). Conclusion The included studies in this meta-analysis were a mix of clinical trials that mostly had a high risk of bias and prospective cohort studies with mostly moderate quality. The failure rate of miniscrews was modest (13.5%, 95% CI 11.5–15.9) which suggests that miniscrews are clinically reliable. Subgroup analysis showed that with the possible exception of smoking and type of mucosal insertion, the assessed risk factors had very minor effects on miniscrew survival. However, the subgoup analysis should be interpted with caution due to high-level hetrogniety and unbalanced and small groups. High quality RCTs with large sample sizes are required to support the findings of this review. Supplementary material Supplementary material is available at European Journal of Orthodontics online. Conflict of interest None to declare. 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Motoyoshi , M. , Inaba , M. , Ono , A. , Ueno , S. and Shimizu , N . ( 2009 ) The effect of cortical bone thickness on the stability of orthodontic mini-implants and on the stress distribution in surrounding bone . International Journal of Oral and Maxillofacial Surgery , 38 , 13 – 18 . Google Scholar CrossRef Search ADS PubMed 68. Miyazawa , K. , Kawaguchi , M. , Tabuchi , M. and Goto , S . ( 2010 ) Accurate pre-surgical determination for self-drilling miniscrew implant placement using surgical guides and cone-beam computed tomography . European Journal of Orthodontics , 32 , 735 – 740 . Google Scholar CrossRef Search ADS PubMed 69. Luzi , C. , Verna , C. and Melsen , B . ( 2007 ) A prospective clinical investigation of the failure rate of immediately loaded mini-implants used for orthodontic anchorage . Progress in Orthodontics , 8 , 192 – 201 . Google Scholar PubMed 70. Iwai , H. , Motoyoshi , M. , Uchida , Y. , Matsuoka , M. and Shimizu , N . 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Lim , H.J. , Eun , C.S. , Cho , J.H. , Lee , K.H. and Hwang , H.S . ( 2009 ) Factors associated with initial stability of miniscrews for orthodontic treatment . American Journal of Orthodontics and Dentofacial Orthopedics , 136 , 236 – 242 . Google Scholar CrossRef Search ADS PubMed 85. Melsen , B. and Verna , C . ( 2005 ) Miniscrew implants: the Aarhus anchorage system . Seminars in Orthodontics , 11 , 24 – 31 . Google Scholar CrossRef Search ADS © The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The European Journal of Orthodontics Oxford University Press

Miniscrews failure rate in orthodontics: systematic review and meta-analysis

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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com
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0141-5387
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10.1093/ejo/cjx093
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Abstract

Abstract Background Miniscrews in orthodontics have been mainly used for anchorage without patient compliance in orthodontic treatment. The literature has reported changing failure rates. Objective The aim of this review was to provide a precise estimation of miniscrew failure rate and the possible risk factors of the mechanically-retained miniscrews. Search method Electronic search in database was undertaken up to July 2017 through the Cochrane Database of Systematic Reviews, MEDLINE, Scopus, and Ovid. Additional searching for on-going and unpublished data, hand search of relevant journals and grey lietraure were also undertaken, authors were contacted, and reference lists screened. Eligibility criteria Randomised controlled trials (RCTs) and prospective cohort studies (PCSs), published in English were obtained, which reported the failure rate of miniscrews, as orthodontic anchorage, with less than 2 mm diameter. Data collection and analysis Blind and induplicate study selection, data extraction, and risk of bias assessment were undertaken in this research. Failure rates and relevant risk factors of miniscrews with the corresponding 95 per cent confidence intervals (CIs) were calculated by using the random-effects model. The heterogeneity across the studies was assessed using the I2 and Chi2 test. The risk of bias was assessed using Cochrane risk of bias and Newcastle-Ottawa Scale. Subgroup and sensitivity analyses were performed in order to test the robustness of the results in meta-analysis. Results The 16 RCTs and 30 PCSs were included in this research. Five studies were not included in the meta-analysis due to a lack of the statistical information needed to compute the effect sizes. About 3250 miniscrews from 41 studies were pooled in a random-effect model. The overall failure rate of miniscrews was 13.5 per cent (95% CI 11.5–15.9). Subgroup analysis showed that miniscrews ‘diameter, length and design, patient age, and jaw of insertion had minimal effect on rate of miniscrews failure while the type of the gingivae and smoking had statistically significant effect. Conclusion Miniscrews have an acceptably low failure rate. The findings should be interpreted with caution due to high-level of heterogeneity and unbalanced groups in the included studies. High quality randomized clinical trial with large sample sizes are required to support the findings of this review. Introduction Orthodontic skeletal anchorage devices are used by orthodontists for a range of clinical applications. These include molar distalization, molar protraction, intrusion of incisors, intrusion of molars, cross bite or scissor bite correction, and anchorage reinforcement (1–7). It was following Konami’s publication in 1997 that orthodontic skeletal anchorage devices, as we know them today, were popularized (8). Orthodontic skeletal anchorage devices can broadly be divided into two categories: osseo-integrated implants such as mid-palatal implants (9) and on-plants (10), and mechanically retained devices such as titanium mini-plates (11, 12), zygomatic wires, and miniscrews (13, 14). The use of miniscrews has increased in orthodontics treatment due to their ease of insertion and removal, reasonable cost, biocompatibility, and capability to withstand orthodontic forces (15, 16). Publications regarding the mechanically retained miniscrews increased dramatically from a few papers in the 1980s to above 5000 papers up until year 2017, indicating a huge interest in skeletal anchorage. Unfortunately, the vast majority of these papers are case reports and biological science research and very few are clinical trials published. Miniscrews should ideally remain stationary when orthodontic force is applied to be effective. The miniscrews stability has become a problem because it does not ground on the osseointegration, but it depends on mechanical locking of threads into the bony tissues and they consequently could hold up the orthodontic loading. Several factors contribute to the success of miniscrews which may be related to the design, related to patient, or related to clinician factors. Age is a factor related to patient with a higher failure rate reported in adolescents as compared to adults as a result of the difference in the buccal plate thickness (17). Poor oral hygiene and smoking are further factors related to patient that reduce the survival rate of miniscrews (18–20). Insertion site and type of the mucosa (keratinized and non-keratinized mucosa) are further patient-related factors. In general, miniscrews have been reported to have a good success rate if inserted in the maxillary region and through keratinized gingivae (17, 19, 21). With regard to miniscrew design factors, it has previously been concluded that miniscrews with a diameter between 1.1 and 1.6 mm provide the best success rate (22). Similarly, miniscrews longer than 5–8 mm are more stable than shorter ones (19, 22). Clinician’s experience, sterilization and asepsis, loading protocol (23), implant placement torque (24, 25), and insertion angle (26) have all been implicated as clinician related factors that may significantly affect the survival of miniscrews. Recent reviews investigated the effectiveness of all types of skeletal anchorage devices in anchorage provision in relation to conventional methods (7, 27, 28). However, the findings of these reviews were not specific to the most commonly used skeletal anchorage device, that is mechanically retained miniscrews. As the determination of specific clinical parameters which influence the clinical success has become critical, aim of this study was to conduct a systematic review and meta-analysis of controlled and uncontrolled prospective clinical trials to amend the actual knowledge about the miniscrews in orthodontic clinical practice, specifically about their stability and their associated risk factors. Methods This review received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. This systematic review was planned and reported accordingly with the preferred reporting items for systematic review and meta-analysis (29) and Cochrane Guidelines for Systematic Reviews (30). This review was registered with International prospective register of systematic reviews (PROSPERO, number CRD42017071441). Criteria for included studies The main research question was defined in PICO format (Table 1). The included studies in this systematic review were human randmosied clinical trials (RCTs) and prospective cohort studies (PCSs) that were published in English till the date July 2017. There was no restriction in the search strategy about the starting date. Since the nature of this study was to aggregate the failure rates of miniscrews, therefore no comparators were needed. Articles on miniscrews with a diameter greater than 2 mm, miniscrews in vitro studies, animal studies, case reports and case series, and review articles were excluded from this research. In cases of unclear study design, the author was contacted twice for further information. If there was no response from the author, the study was excluded. Table 1. PICO format. Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure View Large Table 1. PICO format. Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure Population Participants having orthodontic treatment (in primary, secondary or tertiary care setting) and requiring the insertion of miniscrews (less than 2 mm) with no restriction over the type of orthodontic appliance, gender, or the presenting age of the patients Intervention and comparators Any orthodontic treatment intervention involving the insertion of miniscrews Outcome Primary outcome was the failure demonstrated by mobility, infection, inflammation or other factors leading to the premature loss of the miniscrews for the predefined study period Secondary outcomes were the confounders and risk factors associated with miniscrews’ failure View Large Search strategy Controlled vocabulary and free text terms was used to allocate published, ongoing, and unpublished studies. The vocabulary was updated by following the initial search, if necessary, so as to identify all studies to be considered in this review. The following databases were searched until 1st of July 2017 (Supplementary Table 1): MEDLINE via PubMed, Cochrane Database of Systematic Reviews; Scopus and Ovid. Other bibliographic databases were also searched for ongoing and unpublished data including dissertation data, grey literature in Europe, clinical trial registry, ISRCTN registry, dissertation, and theses dissemination as well as Google Scholar until July 2017. A manual search was also carried out in relevant orthodontic journals until July 2017. Reference lists of the included articles and other relevant systematic reviews related to the topic were checked for any additional relevant literature and also to include an additional controlled vocabulary and free text terms if present. The Cohen kappa statistic was used to assess the agreement between the two review authors. Study selection and data extraction Endnote reference manager software was used for removing duplicate studies. Relevant articles were identified first after reading their titles and abstracts. The full text of the potential articles was assessed for eligibility by two reviewers (F.A. and D.B.). With the potential difficulties encountered while translating multiple articles into English, it was decided to only include articles presenting with a full text in English. However, this exclusion criterion was applied following the primary search so as to avoid bias in the search protocol. Two reviewer (F.A., M.A.) blindly and independently extracted study characteristics and outcomes using the customized data extraction form developed by Papadopoulos and his colleagues (7) with the potential disagreements solved by a third reviewer (D.B.). The following information was included for each study: year of publication, setting, study design, number of miniscrews and their characteristics, success criteria, failure rate, and handling of failure. Assessment of risk bias in the included studies RCTs were assessed for risk of bias using the Cochrane collaboration’s tool (30). Each included study was assessed for the risk of bias in 1. random sequence generation; 2. allocation concealment; 3. blinding of outcome assessors; 4. incomplete outcome data; 5. selective reporting; and 6. other sources of bias. Each RCT was assigned an overall risk of bias, for example, low risk if all key domains have low risk, high risk if more than one key domain has high risk and unclear risk if more than one key domain has unclear risk. PCSs were assessed for risk of bias using the Newcastle–Ottawa Scale (NOS)(31). The NOS assesses the studies in the following three domains: 1. selection; 2. comparability; and 3. outcome. In case of disagreement between the two reviewers, a mutual decision through discussion was made. Again, The Cohen kappa statistic was used to assess the agreement between the two review authors with the potential disagreements solved by a third reviewer. Data synthesis and meta-analysis To calculate the failure rate of miniscrews, the original outcome data were pooled in a random-effect model by using the statistical software Comprehensive Meta-Analysis (Biostat Inc., Englewood, New Jersey, USA) and a significance level of 5% was adopted for all analyses. The pooled estimate was computed from studies that reported similar intervention and outcomes. Failures of miniscrew implants were expressed as event rates with their 95 per cent confidence intervals (CI). Taking in consideration the methodological and statistical heterogeneity, a random-effects model was used to assess all pooled estimates (32). The heterogeneity across the studies was assessed using the I2 and Chi2 test for heterogeneity (no heterogeneity = 0%, low = 25–49%, moderate = 50–74%, and high 75–100%) (33). Other analysis Subgroup and stratified analyses were pre-planned and pre-specified (a priori) to explore the effect of miniscrews’ length, diameter, age group, jaw, the study design (RCT or cohort), and sample size (100 TADs and more) pooled estimate. We also planned to explore the effect of the miniscrew design, self-drilling miniscrews, and non-self-drilling miniscrews that require pre-drilling pilot hole before insertion, on the pooled estimate. Subgroup analyses were planned to be used for a minimum of five studies. Assessment of publication bias Publication bias was assessed by visually inspecting the funnel plot asymmetry. Moreover, two statistical methods were used to produce significance tests in order to recognize publication bias: Begg/Mazumdar’s method (34) and Egger’s method (35). Results Study characteristics There were 8636 hits from both electronic and manual searches. After duplicate removal, studies were screened and in the result 7915 studies did not meet the inclusion criteria on the basis of title and abstract (Figure 1). Another 152 of the qualifying studies were excluded after their full texts were retrieved. This was because they were laboratory studies, retrospective studies, systematic reviews, or not relevant to the review topic. The final sample included 46 studies that met the primary inclusion criteria. The included studies were 16 RCTs (36–51) and 30 PCSs (24, 52–80). Among the PCSs there was 1 split mouth study. Five studies, two RCTs and three PCSs were not included in the meta-analysis due to a lack of the statistical information needed to compute the effect sizes (37, 47, 56, 58, 79). However, they were included in the quality assessment of the studies. The authors were contacted twice via email when necessary to obtain more information and, if no reply was received, the study was excluded. Figure 1. View largeDownload slide Flow chart of the selection of studies. Figure 1. View largeDownload slide Flow chart of the selection of studies. The main characteristics of the 46 included studies which collectively included 3466 miniscrews are presented in Table 2. With respect to the setting of study, 36 (78%) of the studies were based purely on university settings, while the other 10 studies took place in either private, hospital, mixed, or unknown settings. Generally, the number of miniscrews used per participant ranged from 1 to 4 miniscrews and the average number per study was approximately 77 miniscrews. Table 2. Characteristics of included studies. Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded PCS, prospective cohort study; RCT, randomised clinical trial. View Large Table 2. Characteristics of included studies. Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded Author Design Setting No. of patients No. of miniscrews Type of miniscrews Dimensions Success criteria Failure rate (%) Handling of failure Total Patient (per jaw) Diameter (mm) Length (mm) Aboul-Ela et al. (40) RCT University 13 26 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.3 8 Stability 7.7 Repositioned Al-Sibaie and Hajeer (38) RCT University 30 56 2 (2) Dewimed®, Tuttlingen, Germany 1.6 7 Stability 5% Replaced Alves et al. (52) PCS University 15 41 2–3 (2–3) (INP, São Paulo, Brazil) 1.4/2 6/8 Not recorded 14.6 Replaced Apel et al. (53) PCS University 25 76 2–4 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Stability/Infection 10.5 Excluded Basha et al. (41) RCT University 14 14 2 (2) Stainless steel 1.3 8 Stability 28.6 Replaced Bayat and Bauss (54) PCS Private 88 110 1–4 (1–2) LOMAS (Mondeal Medical Systems, Tuttlingen,Germany) 2 7/ 9 /11 Stability/Infection 18.2 Not recorded Bechtold et al. (42) RCT University 30 76 1–2 (1–2) Orlus 18107, Ortholution 1.8 7 Not recorded 13.4% Replaced Berens et al. (61) PCS Private 85 239 1–3 (1–2) AbsoAnchor (Dentos, Daegu, Korea)/ Dual-Top (Jeil Medical, Seoul, Korea) 1.4/1.8/2 Not recorded Stability 15.1 Rescrewed/ excluded Blaya et al. (66) PCS University/private 30 30 1 (1) Sin Implant System (São Paulo, Brazil) 1.2 10 Stability 0 Not recorded Chaddad et al. (43) RCT Not recorded 10 32 2–4 (2) C-Implant (Implantium,Seou, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.4-2 6-10 Stability/infection/treatment completion 12.5 Not recorded Cheng et al. (65) PCS University 44 92 Not recorded Leibinger (Freiburg, Germany)/Mondeal (Tuttlingen, Germany) 2 5-15 Stability/infection/treatment completion 8.7 Not recorded Davoody et al. (77) PCS University 25 26 2 (2) NR 1.8-2 8-9 Not recorded 16% Replaced El-Beialy et al. (64) PCS University 12 40 Not recorded AbsoAnchor (Dentos, Daegu, Korea) 1.2 8 Stability 17.5 Excluded Falkensammer et al. (37) RCT University 26 Not recorded Not recorded Dual Top G2 8x6mm, JeilMedical Corporation, Seoul, Korea) 1.6 8 Not recorded NR Not recorded Garfinkle et al. (44) PCS University 13 82 4–8 (4) Osteomed (Addison, Tex) 1.6 6 Stability/treatment completion 19.5 Not recorded Gelgör et al. (63) PCS University 25 25 1 (1) IMF Stryker (Leibinger, Germany) 1.8 14 Stability 0 Not recorded Gupta et al. (55) PCS University 20 40 2(2) Custome made (Denticon, Mumbai) 1.4 8 Stability 22.5 Not recorded Hedayati et al. (62) PCS University 10 27 3 (1–2) Orthognathic screws 2 9/11 Stability 18.5 Repositioned Herman et al. (71) PCS Not recorded 16 49 1-2 (1–2) Ortho Implant (IMTEC, Ardmore, Okla), Sendax MDI 1.8 6/8/10 Stability 40.8 New/Excluded Iwai et al. (70) PCS University 80 142 2 (2) Orthodontic anchor screws (ISA, BIODENT, Tokyo, Japan) 1.6 8 Stability/mobility/contacted root 8.5%-5.6% Not recorded Khanna et al. (56) PCS University 25 100 Not recorded S.K. Surgical Pvt. Ltd. 1.3 9 Not recorded Not recorded Not recorded Kim et al. (57) PCS University 25 50 2 (2) C-Implant (Implantium, Seoul, Korea) 1.8 8.5 Stability 4 Replaced Lehnen et al. (45) RCT Not recorded 25 60 2 (2) Tomas-pin (Dentaurum, Ispringen, Germany) 1.6 8 Not recorded 11.7 Excluded Liu et al. (46) RCT Not recorded 34 68 2 (2) (Cibei, Ningbo, China) 1.2 8 Stability 11.8 Replaced Luzi et al. (69) PCS University 98 140 Not recorded Aarhus Mini-Implants (Medicon, Germany) 1.5/2 9.6/11.6 Stability/treatment completion 15.7 Excluded Ma et al. (47) RCT University 60 4 (2) AbsoAnchor (Dentos, Daegu, Korea)/Dual-Top (Jeil Medical, Seoul, Korea) 1.8 5/ 6 Not recorded Not recorded Not recorded Miyazawa et al. (68) PCS University 18 44 Not recorded (Jeil Medical, Seoul, Korea) 1.6 8 Treatment completion 9.1 Not recorded Motoyoshi et al. (24) PCS University 41 124 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 14.5 Not recorded Motoyoshi et al. (76) PCS University 57 169 1–4 (1–2) (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 14.8 Not recorded Motoyoshi et al. (74) PCS University 32 87 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 12.6 Not recorded Motoyoshi et al. (67) PCS University 52 148 Not recorded ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability 9.5 Excluded Motoyoshi et al. (75) PCS University 65 209 1–4 (1–2) ISA orthodontic implants (BIODENT, Tokyo, Japan) 1.6 8 Stability/treatment completion 11.5 Not recorded Polat-Ozsoy et al. (80) PCS University 11 22 2 (2) AbsoAnchor (Dentos, Daegu, Korea) 1.2 6 Stability/Infection 13.6 Replaced Sandler et al. (36) RCT Hospital 71 44 2(2) American Orthodontics 1.6 8 Not recorded 2.8% Not recorded Sar et al. (58) PCS University 28 28 2(2) Stryker, Leibinger, Germany 2 8 Not recorded Not recorded Not recorded Sarul et al. (73) Split mouth PCS University 27 54 2 (2) OrthoEasy Pin (Forestadent, Phorzheim, Germany) Not recorded 6/ 8 Mobility/stability 26% Not recorded Sharma et al. (39) RCT University 46 30 2(2) Denticon 1.2 8 Stability 3% Replaced Son et al. (78) PCS University 70 140 2 (2) (ISA self-drill type anchor screw; Biodent, Tokyo, Japan) 1.6 8 Mobility/stability 4% Not recorded Thiruvenkatachari et al. (72) PCS University 10 18 1–2 (1–2) Titanium microimplant 1.3 8 Stability 0 Not recorded Türköz et al. (48) RCT University 62 112 1–2 (1–2) AbsoAnchor (Dentos, Daegu, Korea) 1.4 7 Stability 22.3 Not recorded Yoo et al. (60) PCS University 132 227 Not recorded Biomaterial Korea 1.5 7 Stability/problems in loading 19.5 Not recorded Upadhyay et al. (49) RCT University 33 72 4 (2) Modified Ti fixation screws 1.3 8 Stability 6.9 Replaced Upadhyay et al. (51) PCS University 30 30 2 (2) Modified Ti fixation screws 1.3 8 Stability 10 Replaced Upadhyay et al. (59) PCS University 40 46 2 (2) Ti mini-implants 1.3 8 Not recorded 4.3 Replaced Upadhyay et al. (79) PCS University 34 28 2 (2) Ti mini-implants 1.3 8 Not recorded Not recorded Not recorded Wiechmann et al. (50) RCT Not recorded 49 133 AbsoAnchor (Dentos, Daegu, Korea)/dual-Top (Jeil Medical, Seoul, Korea) 1.2/1.6 5/10 Stability/treatment completion/infection 23.3 Not recorded PCS, prospective cohort study; RCT, randomised clinical trial. View Large There was considerable variation between the miniscrews’ manufacturers used in the included studies and in the dimensions of the inserted miniscrews. The diameter of the inserted miniscrews ranged from 1.2 to 2 mm and their length ranged from 5 to 15 mm. As presented, the recorded failure rate of miniscrews in the included studies also ranged from zero to 40.8 per cent. Risk of bias of included studies The random sequence generation domain was assessed as adequate in nine trials of the included RCTs while the remaining trials were assessed as having high risk of bias or unclear risk (Table 3). Allocation concealment domain was graded as having low risk of bias in five trials only and the rest of the studies were assessed as having unclear risk of bias or high risk of bias. The blinding of participants and personnel was not possible in the included trials due to the nature of orthodontic treatment. However, blinding of assessors was possible and was carried out in 6 trials, in the remaining 10 studies either blinding was not performed or the reporting was not adequate. There were no dropouts in the included trials. Therefore, all included trials were assessed as having low risk of bias. Selective bias domain was judged to have a low risk of bias in three trials. The remaining studies were judged to have unclear risk of bias because no information was reported to allow judgment. The summary judgment of risk of bias was assessed to be low in four trials only (36–39). The remaining trials were judged to have overall high risk of bias after all six domains’ assessment was performed (40–51). Table 3. Risk of bias assessment of the included RCTs. Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk CCT, controlled clinical trial; RCT, randomized clinical trial. View Large Table 3. Risk of bias assessment of the included RCTs. Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk Author Study type Random sequence generation Allocation concealment Blinding of outcome assessors Incomplete outcome data Selective reporting Other bias Overall risk of bias Aboul-Ela et al. (40) RCT Yes Unclear No Yes Unclear No High risk Al-Sibaie and Hajeer (38) RCT Yes Yes Yes Yes Yes Yes Low risk Basha et al. (41) CCT No No No Yes Unclear Yes High risk Bechtold et al. (42) RCT Yes Unclear No Yes Unclear No High risk Chaddad et al. (43) CCT No No No Yes Unclear No High risk Falkensammer et al. (37) RCT Yes Yes Yes Yes Unclear Yes Low risk Garfinkle et al. (44) RCT Unclear Unclear No Yes Unclear No High risk Lehnen et al. (45) RCT Unclear Unclear Yes Yes Unclear Yes High risk Liu et al. (46) RCT Yes Unclear No Yes Unclear No High risk Ma et al. (47) RCT Yes Unclear Yes Yes Unclear No High risk Sandler et al. (36) RCT Yes Yes Yes Yes Yes No Low risk Sharma et al. (39) RCT Yes Yes Yes Yes Yes Yes Low risk Türköz et al. (48) RCT Unclear Unclear No Yes Unclear No High risk Upadhyay et al. (51) CCT No No No Yes Unclear Yes High risk Upadhyay et al. (49) RCT Yes Yes Unclear Yes Unclear Yes Unclear Wiechmann et al. (50) RCT Unclear Unclear No Yes Unclear Yes High risk CCT, controlled clinical trial; RCT, randomized clinical trial. View Large With regard to the quality assessment of prospective cohort studies, the vast majority of the these studies had mediumquality according to the NOS (24, 52–76) (Table 4). Three studies were judged to have high quality (77–79) and one study was judged to have low quality (80). Table 4. Risk of bias assessment of included cohort studies using Newcastle–Ottawa Scale (NOS). Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High View Large Table 4. Risk of bias assessment of included cohort studies using Newcastle–Ottawa Scale (NOS). Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High Study Selection Comparability Outcome NOS score Overall assessment Representativeness of exposed cohort Selection of non-exposed cohort Ascertainment of exposure Demonstration that outcome of interest was not present at the start of the study Comparability of the cohorts Assessment of outcome Was follow-up long enough? Adequacy of follow-up Alves et al. (52) 1 0 1 1 0 1 1 1 6 Medium Apel et al. (53) 1 0 1 1 0 1 1 1 6 Medium Bayat and Bauss (54) 0 1 1 1 1 0 0 1 5 Medium Berens et al. (61) 1 0 1 1 0 1 1 1 6 Medium Blaya et al. (66) 1 0 1 1 0 1 1 1 6 Medium Cheng et al. (65) 1 0 1 1 0 0 1 1 5 Medium Davoody et al. (77) 1 1 1 1 1 0 1 1 7 High El-Beialy et al. (64) 0 0 1 1 0 1 1 1 5 Medium Gelgör et al. (63) 1 0 1 1 0 1 1 1 6 Medium Gupta et al. (55) 1 1 1 1 0 0 1 1 6 Medium Hedayati et al. (62) 1 0 1 1 0 1 1 1 6 Medium Herman et al. (71) 1 0 1 1 0 1 1 1 6 Medium Iwai et al. (70) 1 1 1 1 0 0 1 1 6 Medium Khanna et al. (56) 1 0 1 1 0 0 1 0 4 Medium Kim et al. (57) 1 0 1 1 0 1 1 1 6 Medium Luzi et al. (69) 1 0 1 1 0 1 1 1 6 Medium Miyazawa et al. (68) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (67) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (76) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (74) 1 0 1 1 0 0 1 1 5 Medium Motoyoshi et al. (75) 1 0 1 1 0 1 1 1 6 Medium Motoyoshi et al. (24) 1 0 1 1 0 0 1 1 5 Medium Polat-Ozsoy et al. (80) 1 0 1 0 0 0 0 1 3 Low Sar et al. (58) 1 0 1 1 0 0 1 1 6 Medium Sarul et al. (73) 1 1 1 1 0 0 1 1 6 Medium Son et al. (78) 1 0 1 1 1 1 1 1 7 High Thiruvenkatachari et al. (72) 1 0 1 1 0 1 1 1 6 Medium Yoo et al. (60) 0 0 1 1 1 1 1 1 6 Medium Upadhyay et al. (59) 1 0 1 1 0 1 1 1 6 Medium Upadhyay et al. (79) 1 0 1 1 1 1 1 1 7 High View Large Overall miniscrews failure rate (primary outcomes) Out of 46 studies, the primary outcome of this review, i.e. failure rate of miniscrews, was reported in 41 studies. Data of 3250 miniscrews were extracted and pooled in a random-effect model. The pooled failure rate was 13.5 per cent (95% CI 11.5–15.9, P = 0.001, I2 = 57.1%) (Figure 2). Data of 1391 miniscrews were extracted from 30 studies that included less than 100 miniscrews for each study that were pooled in a random-effect model. The failure rate of 12.5 per cent miniscrews (95% CI 9.7–16.1, P < 0.001, I2 = 60.23%) was comparable to the summary points estimates of the effect size of all the studies. Data from the 11 studies where each study included more than 100 miniscrews were then analysed in a random-effect model, the total number of miniscrews placed was 1893. The failure rate of miniscrews was 14.3 per cent (95% CI 11.5–17.7, P = 0.027, I2 = 71.5%). Similarly, in studies where more than 100 miniscrews were placed, the rate did not differ considerably from the estimates of the effect size of the main analysis. Figure 2. View largeDownload slide Forest plot of overall miniscrews failure rate (random-effect model). Figure 2. View largeDownload slide Forest plot of overall miniscrews failure rate (random-effect model). Assessment of the miniscrew failure risk factors (secondary outcomes) Miniscrews diameter and length were reported more in studies than any factor except for the location (maxilla or mandible). Diameter, length, age, jaw of insertion, smoking status, and type of soft tissue were investigated (Supplementary Table 2). Associated factors with miniscrews failure were assessed in planned subgroup analysis when possible. Influence of study design on estimating the failure rate of miniscrews was assessed (Supplementary Figure 1). Fourteen RCTs that included 876 miniscrews were pooled in one random-effect model as a part of the sensitivity analysis. Their failure rate was 13.3 per cent (95% CI 9.7–18, Q = 31.5 P < 0.001, I2 = 55.6%). Interestingly, this was very close to the pooled failure rate (13.5%, 95% CI 11.1–16.4, Q = 76.54, P < 0.001, I2 = 67.34%) of 27 PCSs that included 2374 miniscrews. Influence of length and design of miniscrew on the estimation of failure rate of miniscrews was also assessed (Supplementary Figures 2 and 3). The length of 8 mm was used as a cut-off point to assess the effect of length of miniscrews on the failure rate. The failure rate of the long miniscrews equal or greater than 8 mm was (12.2%, 95% CI 6.7–21.4, Q = 15.2, DF = 5, P < 0.001, I2 = 67.2%) and the failure rate for the short miniscrews was 12.7% (95% CI 10.5–15.4, Q = 47.26, P < 0.001, DF = 26, I2 = 44.9%). Data from 11 studies that used non-self-drill miniscrews and 9 studies that used self-drill miniscrews were pooled. Miniscrews failure rate was 14.9 per cent (95% CI 10.4–20.8, Q = 20.7, DF = 8, P < 0.001, I2 = 88.9%) in the non-self-drill miniscrews group which was not significantly different from the estimate effect in the self-drill miniscrews (14.2%, 95% CI 5.6–31.8, Q = 51.57, P < 0.001, I2 = 71.41%). Only one study (54) evaluated the association between smoking and miniscrews failure rate and it included 110 miniscrews. Seventy-three miniscrews were placed in non-smokers, 18 miniscrews for light smokers (≤10 cigarettes/day), and the rest for heavy smokers (≥10 cigarettes/day). The failure rates were 9.5, 11, and 57.8 per cent respectively. Moreover, one trial (43) reported on the influence of type of gingivae at insertion site. Thirty-two miniscrews were included in the study, those were placed in keratinized tissue (11 miniscrews) showed no failure, 4 out of 21 miniscrews (19%) that were placed in non-keratinized tissue failed. Publication bias analysis Supplementary Figure 4 shows a funnel plot of studies where the effect sizes were plotted against standard error. The vertical line represents the estimate of weighted mean effect size. As one would expect, studies with a smaller sample size and large sampling error would scatter toward the bottom of the funnel plot. If publication bias is not present, the data points would normally expect to be distributed symmetrically around the mean effect size estimate. In this current meta-analysis, the shape of the inverted funnel plot was asymmetrical between the right and the left sides of the plot, which means that there was absence of smaller sized studies towards the right side of the plot. Therefore, a considerable publication bias due to a failure of including studies with small effect sizes seems likely in this meta-analysis. Furthermore, both Begg’s test (Kendall’s tua = −0.34535, P = 0.00131) and Egger’s test (−1.789, 95% CI −2.70 to −0.874, P = 0.00017) suggested that publication bias may be present in this meta-analysis. Discussion This systematic review included 16 randomised clinical trials and 30 prospective cohort studies, in which the miniscrews were used to reinforce orthodontic anchorage. The majority of the included trials were judged as having a high risk of bias. In most of these trials, randomization and allocation concealment procedures were either inadequate or reported incompletely. The quality of most of prospective cohort studies was medium. This can be attributed to the fact that most of included cohort studies did not include a comparison group, thus, they had a lower score in the NOS. The meta-analysis estimated the miniscrews failure rate to be 13.5 per cent (95% CI 11.5–15.9). Sensitivity analysis, after excluding small studies, showed almost similar pooled failure rate of miniscrews (14.3%) to the overall estimate effect indicating adequate robustness of the results. This finding differed slightly from the failure rate that was previously reported by Papageorgiou et al. (7) who reported a failure rate of 13.5 per cent (95% CI 11.5–15.8). The minor difference between the two estimates might have resulted from including additional studies in our meta-analysis (38, 42, 55, 59, 60, 77, 78). Secondly, we excluded retrospective studies, studies with unclear design or studies in language other than English that had been included in the previous meta-analysis (80). Associated factors with miniscrews failure were assessed in subgroup analyses. It appeared from the findings of this meta-analysis that miniscrews with diameter smaller than 1.3 mm had lower failure rate (10.7%, 95% CI 7.6–15) when compared with miniscrews with diameter of 1.4–1.6 mm (13.6%, 95% CI 10.3–17.1) and diameter of 1.7–2 mm (14.4%, 95% CI 8.8–23.5). However, the number of included miniscrews with small diameter was 450 while the included miniscrews with medium diameter were 1586 and the ones with large diameter were 391. This variation in sample size between the included miniscrews and the heterogeneity may have influenced the conclusiveness of the findings. Papageorgiou et al. (7) found comparable failure rates for miniscrews of small and large diameter: 10.9 per cent (95% CI 7.7–15.3) and 14.3 per cent (95% CI 7.4–25.8), respectively. However, they found that miniscrews with medium diameter had failure rate of 12.7 per cent (95% CI 8.1–19.3). Lim and his team conducted two retrospective studies and found that the miniscrew diameter had no significant effect on the success of miniscrew (81,82). Furthermore, the difference between large and medium size diameter was minimum, approximately 0.8 per cent. This was proven in previous study that diameter greater than 1.6 mm seems to confer no significant benefit as wide miniscrews are associated with higher risk of root contact than narrow miniscrews (22). The miniscrews in this meta-analysis were subdivided into short (≤8 mm) and long (>8 mm) group. Most of the studies used short miniscrews (Supplementary Table 2). The failure rate of short miniscrews was 12.7 per cent (95% CI 10.5–15.4) which is slightly larger than the failure rate of long miniscrews (8.3%, 95% CI 3.1–20.2). It is at the discretion of the clinician to consider this difference clinically significant or not, but theoretically, longer miniscrews should have a lower failure rate as they offer better mechanical retention in the bone than shorter miniscrew. Lim et al. (82) found higher failure rate (25%) with miniscrews of 6 mm or less, whereas miniscrews longer than 6mm had lower failure rate (<12%). This could be due to the significant heterogeneities in the subgroup analysis, thus, this finding is not conclusive and it should be interpreted with caution. Furthermore, in this review an arbitrary cut-off point of 8 mm was adopted to assess the effect of length of miniscrew on the failure rate; hence, the possibilities of the overlap of the findings on either side of the cut-off point is high, i.e. those miniscrews with 7.9 mm or less will be included in the short group. It is acknowledged that this cut-off point carries weak specificity on the pooled estimate. The design of the miniscrews was compared in a small number of included studies and did not have any effect on the failure rate according to our findings. The failure rate of self-drilling miniscrews was 14.2 per cent (95% CI 5.6–31.8) and for the non-self-drilling it was 14.9 per cent (95% CI 10.4–20.8). Similar finding was reported by Papageorgiou et al. (7) for the non-self-drilling miniscrews (17.7%, 95% CI 5.1–44.9) but was significantly lower in self-drilling group (7.7%, 95% CI 4.8–12.0). This discrepancy might be due to the fact that we extracted the data of miniscrews design from nine studies compared to three studies in Papageorgiou and team review (7), this might have influenced the estimation of the failure rate. Moreover, this could be due to the significant heterogeneities in the subgroup analysis, thus, this finding is not conclusive and it should be interpreted with caution. Interestingly, Chen et al. (17) in their retrospective study found that self-drilling miniscrews had higher failure rate (33%) when compared with non-self-drilling (10%) (83), though this difference was not significant. Age is a patient-related factor with a higher failure rate in adolescents than adults potentially as a result of the difference in the buccal plate thickness (17). In this review, most studies recruited a mix of young (≤18 years) and adult patients (>18 years). The failure rate of miniscrews placed in young patents was 8.6 per cent (95% CI 4.7–15.1) which is lower than the failure rate reported by Papageorgiou et al. (7) who found that the failure rate in patients younger than 20 years was 12.6 (95% CI 6.4–23.3). The difference between the two estimates was not significant and could be the result of the variation in the included studies between the two meta-analyses. Similarly, the failure rate of miniscrews placed in adults according to our analysis was 11.2 per cent (95% CI 6.6–18.7) compared to 15.5 per cent (95% CI 11.2–21.0) in Papageorgiou and team review (7). In contrary, retrospective studies (82, 84) showed that older patients had higher failure rate probably due to smoking and compromised periodontium. Moreover, these findings may simply be a function of sample size, as there were more miniscrews inserted in younger participants than adults. In our analysis, the failure rate of miniscrews placed in the maxilla was 11.0 per cent (95% CI 8.8–13.7) while the failure rate of those placed in the mandible was 16.5 per cent (95% CI 11.6–22.7). The higher failure rate in the mandible may be caused by the greater bone density, the limited amount of cortical bone around the miniscrews, and the narrow vestibule compared with the maxilla (84). However, it is important to consider the significant degree of heterogeneities in the subgroup analysis during interpretation of the data. Data regarding to the effect of smoking on the failure rate of miniscrews was extracted from only one study (54) in our review and it appears that smoking has a negative effect on miniscrew stability although there is very limited data to support this fact. The type of mucosa insertion and its relationship to the miniscres failure rate was investigated in only one study (43). Chaddad and colleagues found that 11 miniscrews placed in the keratinized tissue had no failures. On the other hand, 1 out of 5 miniscrews would fail when it is inserted through the mobile non-keratinised gingivae. Limitations of the study The overal failure rate of the miniscrews should be read with caution due to the significant heterogeneity (Q = 86.34, P > 0.001, I2 = 57.1%) between the studies. This is to be expected because the included studies had different designs, sample sizes and methods. Inspection of the funnel plot and statistically significant Egger’s test and Begg’s test suggested that publication bias is likely to be present. This bias is expected because the included studies in this meta-analysis and not all of the included trials were meta-analysed because the authors did not report data on failure rate of miniscrew. Additionally, the asymmetry in the funnel plot may have raised because of true methodological and statistical heterogeneity. It is worth noting that the funnel plot is able to indicate the presence of the publication bias but it cannot explain the reasons for the asymmetry (83, 85). Conclusion The included studies in this meta-analysis were a mix of clinical trials that mostly had a high risk of bias and prospective cohort studies with mostly moderate quality. The failure rate of miniscrews was modest (13.5%, 95% CI 11.5–15.9) which suggests that miniscrews are clinically reliable. Subgroup analysis showed that with the possible exception of smoking and type of mucosal insertion, the assessed risk factors had very minor effects on miniscrew survival. However, the subgoup analysis should be interpted with caution due to high-level hetrogniety and unbalanced and small groups. High quality RCTs with large sample sizes are required to support the findings of this review. Supplementary material Supplementary material is available at European Journal of Orthodontics online. Conflict of interest None to declare. 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The European Journal of OrthodonticsOxford University Press

Published: Jan 5, 2018

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