Incisor root resorption in class II division 2 patients in relation to orthodontic treatment

Incisor root resorption in class II division 2 patients in relation to orthodontic treatment Summary Background/Objectives The aims were 1. to analyse differences in the occurrence of orthodontic induced inflammatory root resorption (OIIRR) of the upper and lower incisors in Angle Class II division 2 patients, between patients treated with fixed appliance only (one-phase treatment group) and patients treated with removable appliance before treatment with fixed appliance (two-phase treatment group) and 2. to analyse differences in OIIRR between treatment time, age, gender, craniofacial morphology and deviations in the dentition for the two groups together. Materials/Methods Seventy-four subjects treated for Class II division 2 malocclusion were divided into two groups: 46 patients in the one-phase treatment group (28 girls, 18 boys, mean age 14.4) and 28 patients in the two-phase treatment group (18 girls, 10 boys, mean age 12.4) where 336 and 201 incisors were analysed respectively. OIIRR was assessed on intra oral radiographs, deviations of the dentition were assessed on orthopantomograms and the craniofacial morphology was assessed on lateral cephalograms. Differences were tested by Fisher Exact test, McNemar, and multiple regression analysis. Results The one-phase treatment group showed significantly more OIIRR for lower central incisors (P = 0.002) compared to the two-phase treatment group. For the both groups combined, boys showed more OIIRR than girls (P = 0.002) and patients with agenesis showed more OIIRR than patients without agenesis (P = 0.019) for the lower central incisors. Conclusion The results indicate that two-phase treatment modalities may be considered as an option for Angle Class II division 2 patients with enhanced risk for OIIRR. Introduction Orthodontic treatment of Angle Class II division 2 malocclusion requires sufficient torque of the upper incisors to obtain treatment stability (1). It has previously been shown that torque of the upper incisors may enhance the risk of orthodontically induced inflammatory root resorption (OIIRR) (2, 3). The aetiology of OIIRR is complex and multifactorial, and orthodontic treatment is not the only risk factor for inflammatory external apical root resorption. Other predisposing factors are general disorders such as Ectodermal Dysplasia (4), Tuberous Sclerosis (5), Osteogenesis Imperfecta (4), and Paget’s Disease of Bone (6) where the mesenchymal and ectodermal tissue of the teeth and the periodontal ligament is affected. Deviations in the dentition such as Short Root Anomaly (7), unusual root morphology (8), ectopic upper canines (9), multiple agenesis (10), and taurodontism (11) have also been reported to be risk factors for OIIRR. Furthermore, malocclusions such as anterior open bite (12), Angle Class III occlusions (2) and large horizontal overjet (13) as well as functional factors such as nail biting (14) and lip/tongue dysfunction (15) have previously been reported as risk factors for OIIRR. Treatment factors that previously have been reported to be associated with OIIRR are heavy forces (16) and specific tooth movements such as intrusion (17). Associations between OIIRR and treatment time have also been discussed in previous studies (15, 16, 18). Linge and Linge (19) showed, for consecutively-treated patients, that OIIRR occurred significantly less in patients treated in two phases (pre-treatment with removable appliance, followed by fixed appliance) compared to the ones treated in one phase (fixed appliances only), whereas Brin et al. (20) showed no significant differences in OIIRR between one-phase and two-phase treatment modalities in Angle Class II division 1 patients. To our knowledge, differences in OIIRR between one-phase and two-phase treatment modalities have not previously been investigated in Angle Class II division 2 patients. As torque of the upper incisors is necessary in the orthodontic treatment of Angle Class II division 2 patients and as torque movement is associated with an enhanced risk of OIIRR, it seems clinically relevant to focus on the occurrence of OIIRR in Angle class II division 2 patients treated with different treatment modalities. The aims were 1. to analyse differences in the occurrence of OIIRR of the upper and lower incisors in Angle Class II division 2 patients, between patients treated with fixed appliance only (one-phase treatment group) and patients treated with removable appliance before treatment with fixed appliance (two-phase treatment group) and 2. to analyse difference in OIIRR between treatment time, age, gender, craniofacial morphology, and deviations in the dentition in the two groups together. Subjects Radiographs from all children and adolescents with Angle class II division 2 who were orthodontically treated between 2009–2015 at the Postgraduate Clinic in Orthodontics, Department of Odontology, University of Copenhagen and who met the inclusion criteria below, were included in the study. The inclusion criteria were: at least half distal molar relationship on one side (21); retroclined upper incisors (ILs/NL < 1 SD (104°), (22); positive vertical overbite; patients treated orthodontically, with none-extraction therapy and with conventional brackets during the phase with fixed appliance. Exclusion criteria: incomplete exposed teeth due to film displacement; incomplete exposed roots due to overlapping adjacent teeth; root filled incisors; distorted x-rays due to positioning error; patients treated with self-ligating bracket systems and teeth showing signs of resorption prior to orthodontic treatment (Figure 1). Figure 1. View largeDownload slide Flowchart. Figure 1. View largeDownload slide Flowchart. The patients were treated with two different treatment modalities and were divided accordingly: the “one-phase treatment group” where the patients were treated with fixed appliance only and the “two-phase treatment group” where the pre-treatment consisted of expansion plates, followed with or without treatment with functional appliances (Modified Andresen (23), Bionator (24), or Teuscher (25) with high pull headgear) and finishing in fixed appliance. For all patients the fixed appliance consisted of conventional brackets (American Orthodontics Roth, Dentaurum, Ultra-Minitrim, Ispringen, Germany) and all patients were treated with class II mechanisms including Class II and/or vertical settling elastics without any extractions. The one-phase treatment group consisted of 46 patients (28 girls and 18 boys, mean age 14.2 years, range 11.0–16.7 years) and the two-phase treatment group consisted of 28 patients (18 girls and 10 boys, mean age 12.3 years, range 10.3–15.1 years). 336 and 201 upper and lower incisors were analysed in the two groups, respectively. The mean horizontal overjet was 3.4 mm (range 0.9–4.5 mm), and the mean vertical overbite was 5.9 mm (range 3.5–9.3 mm). The means of the craniofacial morphology is shown in Table 1. Table 1. Differences in age, treatment time, and dentofacial morphology between the two groups. Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  View Large Table 1. Differences in age, treatment time, and dentofacial morphology between the two groups. Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  View Large When power analysis was performed using the mean prevalence of OIIRR reported in the two studies performed on OIIRR in one-phase versus two-phase treatment of consecutively-treated patients and Angle class II div. 1 patients (19, 20) at least 24 subjects in each group were required to have sufficient power (80%) to identify statistically significant differences at the 5% level of significance. The protocol was approved by The Danish Data Protection Agency (no: 2014-54-0830). Methods OIIRR was assessed on intra oral radiographs. Deviations of dentition were assessed on orthopantomograms and craniofacial morphology was assessed on lateral cephalograms. OIIRR The digital peri apical intra oral radiographs of the upper and lower incisors taken before any orthodontic treatment and directly after debonding of fixed appliance were obtained by Eggen holders (26). The radiographs were taken in an “Oralix 65s” unit (2010, Philips N.V. Amsterdam, Netherlands). The exposure values were between 63 kV, 8 mA and 0.26–0.32 s, depending on the age of the patient. All the radiographs were examined on the same monitor (Dell U2312HM Round Rock, Texas, USA). The software used for examining the x-rays was Arion, version 3.41.0 (ProCuris AB, Lund, Sweden). All radiographs were set to equal settings: Scale: 1:1, DPI: 670, Zoom: 1.04. The upper and lower incisors were examined before and after treatment in a blinded fashion, i.e. the examiner was unaware of the performed treatment modality. The formula presented by Linge and Linge (15) was used to compensate for radiographs taken with different angles in different stages. The OIIRR was analysed according to a standard method described by Levander and Malmgren (8), with modification and classified into three grades according to previous studies (e.g. 17, 20): 0) No resorption/irregular root contour (Original grades 0–1); 1) Apical resorption up to one-third of the root length (Original grades 2–3); 2) Apical resorption more than one-third of the root length (Original grade 4). Because of very low prevalence of teeth showing apical resorption more than one-third of the root length (0.9%), grades 1 and 2 were merged. OIIRR was then described as “No resorption/irregular root contour” or “Apical resorption”. Contralateral teeth were paired and the most severe side was registered. Each tooth group was described separately. The prevalence of OIIRR in the two groups is shown in Figure 2. Figure 2. View largeDownload slide Difference in the occurrence of teeth with OIIRR (%) between the two treatment groups. Contralateral teeth pooled. Figure 2. View largeDownload slide Difference in the occurrence of teeth with OIIRR (%) between the two treatment groups. Contralateral teeth pooled. Dentition The orthopantomograms were taken before treatment in a Promax RPX241636 unit (2012, Planmeca, Helsinki, Finland). The exposure values were 66–68 kV, 7–8 mA and 16 s, depending on the age of the patient. The software for analysing the radiographs was Arion, version 3.41.0 (ProCuris AB, Lund, Sweden). Deviations in the dentition were registered as “yes/no” as follows: Tooth agenesis of the upper and lower permanent incisors and premolars (27); Taurodontism of the first and second upper and lower permanent first and second molars (28). Craniofacial morphology Before treatment, lateral cephalograms were taken of the patients standing in the natural head posture with their teeth in occlusion (29) in a Promax ProCeph RPX241636 unit (2012, Planmeca, Helsinki, Finland). Exposure values were: 66–68 kV, 16 mA and 0.32–0.40 s, depending on the age of the patient. The lateral cephalograms were digitized by Tiops 4 (Total Interactive Orthodontic Planning System, version 3.4.10.0, Copenhagen, Denmark) and the craniofacial morphology was analysed according to Björk (22) (Table 1 and Figure 3). Figure 3. View largeDownload slide Illustration of points and lines describing the craniofacial morphology (22). Points are: n: Nasion, s: Sella, ba: Basion, sp: Spinal Point, ss: Subspinale, pm: Pterygomaxillare, sm: Supramentale, gn: Gnathion, mlp: Mandibular Line Posterior. Lines; NSL: Nasion-Sella-Line, NL: Nasal line, ML: Mandibular line, ILs: Incisal edge—apex of the maxillary incisors, ILi: Incisal edge—apex of the mandibular incisors. Figure 3. View largeDownload slide Illustration of points and lines describing the craniofacial morphology (22). Points are: n: Nasion, s: Sella, ba: Basion, sp: Spinal Point, ss: Subspinale, pm: Pterygomaxillare, sm: Supramentale, gn: Gnathion, mlp: Mandibular Line Posterior. Lines; NSL: Nasion-Sella-Line, NL: Nasal line, ML: Mandibular line, ILs: Incisal edge—apex of the maxillary incisors, ILi: Incisal edge—apex of the mandibular incisors. Reliability For assessment of the reliability of OIIRR 50 teeth were re-analysed after 1 week. The Cohen’s kappa-test (30) showed excellent intra-individual agreement (K = 0.92). For assessment of the reliability of the craniofacial measurement 25 lateral cephalograms were re-traced after one week and no systematic error was found. The method error ranged between 0.2 and 1.4 degrees (31) and the reliability coefficient ranged between 0.96 and 1.00 (32). Statistical analysis SPSS software version 22.0 (IBM Inc. Chicago, Illinois, USA) was used for the statistical analyses. The results were considered to be significant at P values below 0.05. For descriptive statistics t-test, chi-square and Fisher’s Exact were performed. For difference in OIIRR regarding treatment groups and gender, chi-square was performed. For deviations in the dentition Fisher’s exact test was performed. For difference in OIIRR regarding treatment time and craniofacial deviations, logistic regression analyses were performed adjusted for age and gender. Results Differences in age, treatment time, and dentofacial morphology between the two groups are shown in Table 1. The patients in the one-phase treatment group were significantly older than the patients in the two-phase treatment group at treatment start (P < 0.001) and when the fixed appliance was applied in the two-phase treatment group (P < 0.01). The treatment time for fixed appliance in the one-phase treatment group was significantly longer than for the two-phase treatment group (P < 0.001). Agenesis occurred significantly more often in the one-phase treatment group compared to the two-phase treatment group (P = 0.040). For taurodontism, gender, total treatment time and craniofacial morphology no significant differences were found between the two groups. Differences in OIIRR between the two treatment groups The one-phase treatment group showed significantly more OIIRR for the lower central incisors compared to the two-phase treatment group (31.0% versus 7.7%, P = 0.025; Figure 2). The same pattern also applied for the lower lateral incisors (26.2% versus 8.0%), but the difference was not significant (P = 0.069, Figure 2). For the upper incisors there was no significant difference in OIIRR between the two groups. Age, gender, treatment time, and dentofacial morphology For the two treatment groups together boys showed more OIIRR than girls (42.3% versus 9.5%, P = 0.002; Figure 4) for lower central incisors and patients with agenesis showed more OIIRR than patients without agenesis (66.7% versus 17.7%, P = 0.019) for the lower central incisors (Figure 5). The same pattern applied also for the lower lateral incisors for gender (30.8% versus 12.1%) and for patients with agenesis (50% versus 16.4%), but the difference was not statistically significant (P = 0.061 and P = 0.082 respectively). For taurodontism, total treatment time and age no significant difference in OIIRR was found. Figure 4 View largeDownload slide Difference in occurrence of OIIRR (%) between girls and boys for the two groups together. Contralateral teeth pooled. Figure 4 View largeDownload slide Difference in occurrence of OIIRR (%) between girls and boys for the two groups together. Contralateral teeth pooled. Figure 5 View largeDownload slide Difference in occurrence of OIIRR (%) for patients with and without agenesis for the two groups together. Contralateral teeth pooled. Figure 5 View largeDownload slide Difference in occurrence of OIIRR (%) for patients with and without agenesis for the two groups together. Contralateral teeth pooled. Discussion The main aim of the present study was to analyse the difference between the occurrence of OIIRR of the upper and lower permanent incisors in Angle Class II division 2 patients in two groups: one group treated with fixed appliance only (one-phase treatment group), the other group pre-treated with removable appliance before treatment with fixed appliance (two-phase treatment group). Except from age and the occurrence of agenesis the two groups were comparable at treatment start. The patients were younger in the two-phase treatment group compared to the one-phase treatment group. This is a limitation in the present study, but the age difference is in agreement with previous studies where one-phase and two-phase Class II treatments were compared in a randomized clinical trial regarding other purposes than OIIRR (33, 34). Due to growth and stage of dentition it is logical that two-phase treatment modalities start somewhat earlier than one-phase treatments (33, 34). Furthermore, all patients with agenesis were located in the one-phase treatment group. An explanation for this may be that patients with agenesis were considered to need more extensive orthodontic treatment. Therefore, treatment with fixed appliance was considered inevitable and begun immediately. The functional appliance in the two-phase treatment group was not standardised in the present study as three functional appliances (modified Andresen, Bionator, and Teuscher) with and without torque springs were used. Even though the appliances are well defined in the literature (23–25) it may be a limitation in the present study because the Teuscher activator has torque springs (25). This may affect the results of the present study as torque of the upper incisors may be associated with OIIRR (2, 3). In the present study OIIRR was analysed according to a standard method described by Levander and Malmgren (8) and modified according to previous studies (17, 20) in three grades: “no resorption/irregular root contour”, “apical root resorption < 1/3 of the root length” and “apical root resorption > 1/3 of the root length”. Because only 0.9% of the patients showed resorption more than one-third of the root, apical root resorption less than or greater than one-third of the root length was merged. Though not sophisticated, the method is a standard method and the method error in the present study showed excellent intra-individual agreement. Differences in OIIRR between the two groups In the present study, there was a significant difference in OIIRR between the one-phase and the two-phase treatment groups for the lower central incisors, where the one-phase treatment groups showed more OIIRR. One explanation for this finding could be that in the two-phase treatment group, the main sagittal and vertical correction of the dentition was probably corrected/partially corrected with removable appliance with the help of alveolar growth and eruption of the dentition (23–25), in contrast to more active forces in the one-phase treatment group (1). In the one-phase treatment group the treatment time for fixed appliance was also significantly longer than that for the two-phase treatment group and Class II elastic mechanism was therefore used for a longer period of time in the one-phase treatment group. In the present study no significant differences in the occurrence of OIIRR for the upper incisors were found. The finding was in agreement with Brin et al. (20) who examined the difference in OIIRR between one-phase and two-phase treatment modalities in Angle Class II division 1 patients. The reason for the lack of difference in OIIRR for the upper incisors between the groups may be because of the same forces and root movements were applied on the upper incisors during the phase with fixed appliances in both treatment groups. Age, gender, treatment time, and dentofacial morphology Boys showed more OIIRR than girls. This is in agreement with some previous studies (13, 35). However, other studies showed that girls are at greater risk for developing OIIRR (11, 12) whereas other studies did not find any difference between genders in the occurrence of OIIRR (36–39). OIIRR was not age dependent, which was in agreement with previous studies (13, 17, 36, 38, 40–43). Several studies have shown that treatment time is significant for OIIRR (13, 15, 16, 18, 20, 44–47), whereas some studies did not show any significance for treatment time and OIIRR (17, 19, 48) as found in the present study. It may be difficult to look at treatment time only, without considering other factors such as severity of the malocclusion (44), amount of tooth movement (41, 46, 47, 49, 50) and the size of the overjet (13, 20, 37), which are factors previously found to be associated with OIIRR. In the present study, the subjects were homogenous, as all the patients were Angle Class II division 2 patients and treated with Class II mechanisms without any extractions. OIIRR occurred significantly more often in patients with agenesis than patients without agenesis. It should be bared in mind that only seven patients in the present study had agenesis. However, the findings are in agreement with previous studies (10, 11, 51). One explanation may be that the innervation of the most vulnerable areas of the dentition is stressed, hence the agenesis and the higher risk of OIIRR (11, 51). Another theory is that patients with agenesis require more extensive dental rehabilitation, which often includes a long period of orthodontic treatment (10). Taurodontism was not associated with the occurrence of OIIRR in the present study. Taurodontism and OIIRR have only been sparsely investigated previously and studies disagree on whether taurodontism may be a risk factor for OIIRR (11, 52). The present study found no significant association between craniofacial morphology and OIIRR, which is in agreement with a previous study (40). One explanation for the lack of a significant difference for craniofacial morphology and OIIRR is that craniofacial morphology may not have any influence on OIIRR. Another explanation may be that all patients included in the present study had Angle Class II division 2 malocclusion, and thus a relatively homogenous anatomical character with respect to craniofacial morphology and malocclusion. Also, all patients were treated with no extractions and with Class II mechanisms in the fixed appliance, regardless of treatment in one- or two-phase modality. Conclusion Patients in the one-phase treatment group showed significantly more OIIRR than patients in the two-phase treatment group for the lower central incisors. Boys showed more OIIRR than girls and patients with agenesis showed more OIIRR than patients without agenesis, in both cases for the lower central incisors. The results indicate that two-phase treatment modalities may be considered as an option for Angle Class II division 2 patients with enhanced risk for OIIRR. Conflict of interest None to declare. Acknowledgement Ib Jarle Christensen, Senior researcher, Department of Gastroenterology, Hvidovre Hospital, Denmark, is acknowledged for statistical assistance. References 1. Nanda, R.S. and Tosun, Y. 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( 1999) Are dental anomalies risk factors for apical root resorption in orthodontic patients? American Journal of Orthodontics and Dentofacial Orthopedics , 116, 187– 195. Google Scholar CrossRef Search ADS   © The Author(s) 2017. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The European Journal of Orthodontics Oxford University Press

Incisor root resorption in class II division 2 patients in relation to orthodontic treatment

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Abstract

Summary Background/Objectives The aims were 1. to analyse differences in the occurrence of orthodontic induced inflammatory root resorption (OIIRR) of the upper and lower incisors in Angle Class II division 2 patients, between patients treated with fixed appliance only (one-phase treatment group) and patients treated with removable appliance before treatment with fixed appliance (two-phase treatment group) and 2. to analyse differences in OIIRR between treatment time, age, gender, craniofacial morphology and deviations in the dentition for the two groups together. Materials/Methods Seventy-four subjects treated for Class II division 2 malocclusion were divided into two groups: 46 patients in the one-phase treatment group (28 girls, 18 boys, mean age 14.4) and 28 patients in the two-phase treatment group (18 girls, 10 boys, mean age 12.4) where 336 and 201 incisors were analysed respectively. OIIRR was assessed on intra oral radiographs, deviations of the dentition were assessed on orthopantomograms and the craniofacial morphology was assessed on lateral cephalograms. Differences were tested by Fisher Exact test, McNemar, and multiple regression analysis. Results The one-phase treatment group showed significantly more OIIRR for lower central incisors (P = 0.002) compared to the two-phase treatment group. For the both groups combined, boys showed more OIIRR than girls (P = 0.002) and patients with agenesis showed more OIIRR than patients without agenesis (P = 0.019) for the lower central incisors. Conclusion The results indicate that two-phase treatment modalities may be considered as an option for Angle Class II division 2 patients with enhanced risk for OIIRR. Introduction Orthodontic treatment of Angle Class II division 2 malocclusion requires sufficient torque of the upper incisors to obtain treatment stability (1). It has previously been shown that torque of the upper incisors may enhance the risk of orthodontically induced inflammatory root resorption (OIIRR) (2, 3). The aetiology of OIIRR is complex and multifactorial, and orthodontic treatment is not the only risk factor for inflammatory external apical root resorption. Other predisposing factors are general disorders such as Ectodermal Dysplasia (4), Tuberous Sclerosis (5), Osteogenesis Imperfecta (4), and Paget’s Disease of Bone (6) where the mesenchymal and ectodermal tissue of the teeth and the periodontal ligament is affected. Deviations in the dentition such as Short Root Anomaly (7), unusual root morphology (8), ectopic upper canines (9), multiple agenesis (10), and taurodontism (11) have also been reported to be risk factors for OIIRR. Furthermore, malocclusions such as anterior open bite (12), Angle Class III occlusions (2) and large horizontal overjet (13) as well as functional factors such as nail biting (14) and lip/tongue dysfunction (15) have previously been reported as risk factors for OIIRR. Treatment factors that previously have been reported to be associated with OIIRR are heavy forces (16) and specific tooth movements such as intrusion (17). Associations between OIIRR and treatment time have also been discussed in previous studies (15, 16, 18). Linge and Linge (19) showed, for consecutively-treated patients, that OIIRR occurred significantly less in patients treated in two phases (pre-treatment with removable appliance, followed by fixed appliance) compared to the ones treated in one phase (fixed appliances only), whereas Brin et al. (20) showed no significant differences in OIIRR between one-phase and two-phase treatment modalities in Angle Class II division 1 patients. To our knowledge, differences in OIIRR between one-phase and two-phase treatment modalities have not previously been investigated in Angle Class II division 2 patients. As torque of the upper incisors is necessary in the orthodontic treatment of Angle Class II division 2 patients and as torque movement is associated with an enhanced risk of OIIRR, it seems clinically relevant to focus on the occurrence of OIIRR in Angle class II division 2 patients treated with different treatment modalities. The aims were 1. to analyse differences in the occurrence of OIIRR of the upper and lower incisors in Angle Class II division 2 patients, between patients treated with fixed appliance only (one-phase treatment group) and patients treated with removable appliance before treatment with fixed appliance (two-phase treatment group) and 2. to analyse difference in OIIRR between treatment time, age, gender, craniofacial morphology, and deviations in the dentition in the two groups together. Subjects Radiographs from all children and adolescents with Angle class II division 2 who were orthodontically treated between 2009–2015 at the Postgraduate Clinic in Orthodontics, Department of Odontology, University of Copenhagen and who met the inclusion criteria below, were included in the study. The inclusion criteria were: at least half distal molar relationship on one side (21); retroclined upper incisors (ILs/NL < 1 SD (104°), (22); positive vertical overbite; patients treated orthodontically, with none-extraction therapy and with conventional brackets during the phase with fixed appliance. Exclusion criteria: incomplete exposed teeth due to film displacement; incomplete exposed roots due to overlapping adjacent teeth; root filled incisors; distorted x-rays due to positioning error; patients treated with self-ligating bracket systems and teeth showing signs of resorption prior to orthodontic treatment (Figure 1). Figure 1. View largeDownload slide Flowchart. Figure 1. View largeDownload slide Flowchart. The patients were treated with two different treatment modalities and were divided accordingly: the “one-phase treatment group” where the patients were treated with fixed appliance only and the “two-phase treatment group” where the pre-treatment consisted of expansion plates, followed with or without treatment with functional appliances (Modified Andresen (23), Bionator (24), or Teuscher (25) with high pull headgear) and finishing in fixed appliance. For all patients the fixed appliance consisted of conventional brackets (American Orthodontics Roth, Dentaurum, Ultra-Minitrim, Ispringen, Germany) and all patients were treated with class II mechanisms including Class II and/or vertical settling elastics without any extractions. The one-phase treatment group consisted of 46 patients (28 girls and 18 boys, mean age 14.2 years, range 11.0–16.7 years) and the two-phase treatment group consisted of 28 patients (18 girls and 10 boys, mean age 12.3 years, range 10.3–15.1 years). 336 and 201 upper and lower incisors were analysed in the two groups, respectively. The mean horizontal overjet was 3.4 mm (range 0.9–4.5 mm), and the mean vertical overbite was 5.9 mm (range 3.5–9.3 mm). The means of the craniofacial morphology is shown in Table 1. Table 1. Differences in age, treatment time, and dentofacial morphology between the two groups. Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  View Large Table 1. Differences in age, treatment time, and dentofacial morphology between the two groups. Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  Variable  One-phase  Two-phase  P value  Age in years before treatment start  14.22 (SD 1.37)  12.33 (SD 1.12)  P < 0.001  Age in years before fixed appliance  14.22 (SD 1.37)  13.38 (SD 1.13)  P < 0.01  Treatment time in fixed appliance  27.20 (SD 7.17)  19.50 (SD 9.31)  P < 0.001  Total treatment time in months  27.20 (SD 7.17)  30.61 (SD 8.40)  NS  n-s-ba°  131.53 (SD 6.04)  131.30 (SD 6.50)  NS  s-n-ss°  81.72 (SD 4.14)  80.91 (SD 4.28)  NS  s-n-sm°  76.74 (SD 3.49)  76.21 (SD 3.85)  NS  ss-n-sm°  5.00 (SD 2.09)  4.81 (SD 1.79)  NS  NSL/NL°  5.96 (SD 3.42)  6.30 (SD 4.02)  NS  NSL/ML°  27.90 (SD 5.04)  27.77 (SD 6.37)  NS  NL/ML°  21.93 (SD 4.10)  21.47 (SD 7.00)  NS  iLs/NL°  94.72 (SD 6.32)  97.29 (SD 6.76)  NS  iLi/ML°  94.40 (SD 6.69)  92.96 (SD 14.03)  NS  Agenesis  N:7 (15.2 %)  N:0  P = 0.040  Taurodontism  N:14 (30.4 %)  N:7 (25.0 %)  NS  View Large When power analysis was performed using the mean prevalence of OIIRR reported in the two studies performed on OIIRR in one-phase versus two-phase treatment of consecutively-treated patients and Angle class II div. 1 patients (19, 20) at least 24 subjects in each group were required to have sufficient power (80%) to identify statistically significant differences at the 5% level of significance. The protocol was approved by The Danish Data Protection Agency (no: 2014-54-0830). Methods OIIRR was assessed on intra oral radiographs. Deviations of dentition were assessed on orthopantomograms and craniofacial morphology was assessed on lateral cephalograms. OIIRR The digital peri apical intra oral radiographs of the upper and lower incisors taken before any orthodontic treatment and directly after debonding of fixed appliance were obtained by Eggen holders (26). The radiographs were taken in an “Oralix 65s” unit (2010, Philips N.V. Amsterdam, Netherlands). The exposure values were between 63 kV, 8 mA and 0.26–0.32 s, depending on the age of the patient. All the radiographs were examined on the same monitor (Dell U2312HM Round Rock, Texas, USA). The software used for examining the x-rays was Arion, version 3.41.0 (ProCuris AB, Lund, Sweden). All radiographs were set to equal settings: Scale: 1:1, DPI: 670, Zoom: 1.04. The upper and lower incisors were examined before and after treatment in a blinded fashion, i.e. the examiner was unaware of the performed treatment modality. The formula presented by Linge and Linge (15) was used to compensate for radiographs taken with different angles in different stages. The OIIRR was analysed according to a standard method described by Levander and Malmgren (8), with modification and classified into three grades according to previous studies (e.g. 17, 20): 0) No resorption/irregular root contour (Original grades 0–1); 1) Apical resorption up to one-third of the root length (Original grades 2–3); 2) Apical resorption more than one-third of the root length (Original grade 4). Because of very low prevalence of teeth showing apical resorption more than one-third of the root length (0.9%), grades 1 and 2 were merged. OIIRR was then described as “No resorption/irregular root contour” or “Apical resorption”. Contralateral teeth were paired and the most severe side was registered. Each tooth group was described separately. The prevalence of OIIRR in the two groups is shown in Figure 2. Figure 2. View largeDownload slide Difference in the occurrence of teeth with OIIRR (%) between the two treatment groups. Contralateral teeth pooled. Figure 2. View largeDownload slide Difference in the occurrence of teeth with OIIRR (%) between the two treatment groups. Contralateral teeth pooled. Dentition The orthopantomograms were taken before treatment in a Promax RPX241636 unit (2012, Planmeca, Helsinki, Finland). The exposure values were 66–68 kV, 7–8 mA and 16 s, depending on the age of the patient. The software for analysing the radiographs was Arion, version 3.41.0 (ProCuris AB, Lund, Sweden). Deviations in the dentition were registered as “yes/no” as follows: Tooth agenesis of the upper and lower permanent incisors and premolars (27); Taurodontism of the first and second upper and lower permanent first and second molars (28). Craniofacial morphology Before treatment, lateral cephalograms were taken of the patients standing in the natural head posture with their teeth in occlusion (29) in a Promax ProCeph RPX241636 unit (2012, Planmeca, Helsinki, Finland). Exposure values were: 66–68 kV, 16 mA and 0.32–0.40 s, depending on the age of the patient. The lateral cephalograms were digitized by Tiops 4 (Total Interactive Orthodontic Planning System, version 3.4.10.0, Copenhagen, Denmark) and the craniofacial morphology was analysed according to Björk (22) (Table 1 and Figure 3). Figure 3. View largeDownload slide Illustration of points and lines describing the craniofacial morphology (22). Points are: n: Nasion, s: Sella, ba: Basion, sp: Spinal Point, ss: Subspinale, pm: Pterygomaxillare, sm: Supramentale, gn: Gnathion, mlp: Mandibular Line Posterior. Lines; NSL: Nasion-Sella-Line, NL: Nasal line, ML: Mandibular line, ILs: Incisal edge—apex of the maxillary incisors, ILi: Incisal edge—apex of the mandibular incisors. Figure 3. View largeDownload slide Illustration of points and lines describing the craniofacial morphology (22). Points are: n: Nasion, s: Sella, ba: Basion, sp: Spinal Point, ss: Subspinale, pm: Pterygomaxillare, sm: Supramentale, gn: Gnathion, mlp: Mandibular Line Posterior. Lines; NSL: Nasion-Sella-Line, NL: Nasal line, ML: Mandibular line, ILs: Incisal edge—apex of the maxillary incisors, ILi: Incisal edge—apex of the mandibular incisors. Reliability For assessment of the reliability of OIIRR 50 teeth were re-analysed after 1 week. The Cohen’s kappa-test (30) showed excellent intra-individual agreement (K = 0.92). For assessment of the reliability of the craniofacial measurement 25 lateral cephalograms were re-traced after one week and no systematic error was found. The method error ranged between 0.2 and 1.4 degrees (31) and the reliability coefficient ranged between 0.96 and 1.00 (32). Statistical analysis SPSS software version 22.0 (IBM Inc. Chicago, Illinois, USA) was used for the statistical analyses. The results were considered to be significant at P values below 0.05. For descriptive statistics t-test, chi-square and Fisher’s Exact were performed. For difference in OIIRR regarding treatment groups and gender, chi-square was performed. For deviations in the dentition Fisher’s exact test was performed. For difference in OIIRR regarding treatment time and craniofacial deviations, logistic regression analyses were performed adjusted for age and gender. Results Differences in age, treatment time, and dentofacial morphology between the two groups are shown in Table 1. The patients in the one-phase treatment group were significantly older than the patients in the two-phase treatment group at treatment start (P < 0.001) and when the fixed appliance was applied in the two-phase treatment group (P < 0.01). The treatment time for fixed appliance in the one-phase treatment group was significantly longer than for the two-phase treatment group (P < 0.001). Agenesis occurred significantly more often in the one-phase treatment group compared to the two-phase treatment group (P = 0.040). For taurodontism, gender, total treatment time and craniofacial morphology no significant differences were found between the two groups. Differences in OIIRR between the two treatment groups The one-phase treatment group showed significantly more OIIRR for the lower central incisors compared to the two-phase treatment group (31.0% versus 7.7%, P = 0.025; Figure 2). The same pattern also applied for the lower lateral incisors (26.2% versus 8.0%), but the difference was not significant (P = 0.069, Figure 2). For the upper incisors there was no significant difference in OIIRR between the two groups. Age, gender, treatment time, and dentofacial morphology For the two treatment groups together boys showed more OIIRR than girls (42.3% versus 9.5%, P = 0.002; Figure 4) for lower central incisors and patients with agenesis showed more OIIRR than patients without agenesis (66.7% versus 17.7%, P = 0.019) for the lower central incisors (Figure 5). The same pattern applied also for the lower lateral incisors for gender (30.8% versus 12.1%) and for patients with agenesis (50% versus 16.4%), but the difference was not statistically significant (P = 0.061 and P = 0.082 respectively). For taurodontism, total treatment time and age no significant difference in OIIRR was found. Figure 4 View largeDownload slide Difference in occurrence of OIIRR (%) between girls and boys for the two groups together. Contralateral teeth pooled. Figure 4 View largeDownload slide Difference in occurrence of OIIRR (%) between girls and boys for the two groups together. Contralateral teeth pooled. Figure 5 View largeDownload slide Difference in occurrence of OIIRR (%) for patients with and without agenesis for the two groups together. Contralateral teeth pooled. Figure 5 View largeDownload slide Difference in occurrence of OIIRR (%) for patients with and without agenesis for the two groups together. Contralateral teeth pooled. Discussion The main aim of the present study was to analyse the difference between the occurrence of OIIRR of the upper and lower permanent incisors in Angle Class II division 2 patients in two groups: one group treated with fixed appliance only (one-phase treatment group), the other group pre-treated with removable appliance before treatment with fixed appliance (two-phase treatment group). Except from age and the occurrence of agenesis the two groups were comparable at treatment start. The patients were younger in the two-phase treatment group compared to the one-phase treatment group. This is a limitation in the present study, but the age difference is in agreement with previous studies where one-phase and two-phase Class II treatments were compared in a randomized clinical trial regarding other purposes than OIIRR (33, 34). Due to growth and stage of dentition it is logical that two-phase treatment modalities start somewhat earlier than one-phase treatments (33, 34). Furthermore, all patients with agenesis were located in the one-phase treatment group. An explanation for this may be that patients with agenesis were considered to need more extensive orthodontic treatment. Therefore, treatment with fixed appliance was considered inevitable and begun immediately. The functional appliance in the two-phase treatment group was not standardised in the present study as three functional appliances (modified Andresen, Bionator, and Teuscher) with and without torque springs were used. Even though the appliances are well defined in the literature (23–25) it may be a limitation in the present study because the Teuscher activator has torque springs (25). This may affect the results of the present study as torque of the upper incisors may be associated with OIIRR (2, 3). In the present study OIIRR was analysed according to a standard method described by Levander and Malmgren (8) and modified according to previous studies (17, 20) in three grades: “no resorption/irregular root contour”, “apical root resorption < 1/3 of the root length” and “apical root resorption > 1/3 of the root length”. Because only 0.9% of the patients showed resorption more than one-third of the root, apical root resorption less than or greater than one-third of the root length was merged. Though not sophisticated, the method is a standard method and the method error in the present study showed excellent intra-individual agreement. Differences in OIIRR between the two groups In the present study, there was a significant difference in OIIRR between the one-phase and the two-phase treatment groups for the lower central incisors, where the one-phase treatment groups showed more OIIRR. One explanation for this finding could be that in the two-phase treatment group, the main sagittal and vertical correction of the dentition was probably corrected/partially corrected with removable appliance with the help of alveolar growth and eruption of the dentition (23–25), in contrast to more active forces in the one-phase treatment group (1). In the one-phase treatment group the treatment time for fixed appliance was also significantly longer than that for the two-phase treatment group and Class II elastic mechanism was therefore used for a longer period of time in the one-phase treatment group. In the present study no significant differences in the occurrence of OIIRR for the upper incisors were found. The finding was in agreement with Brin et al. (20) who examined the difference in OIIRR between one-phase and two-phase treatment modalities in Angle Class II division 1 patients. The reason for the lack of difference in OIIRR for the upper incisors between the groups may be because of the same forces and root movements were applied on the upper incisors during the phase with fixed appliances in both treatment groups. Age, gender, treatment time, and dentofacial morphology Boys showed more OIIRR than girls. This is in agreement with some previous studies (13, 35). However, other studies showed that girls are at greater risk for developing OIIRR (11, 12) whereas other studies did not find any difference between genders in the occurrence of OIIRR (36–39). OIIRR was not age dependent, which was in agreement with previous studies (13, 17, 36, 38, 40–43). Several studies have shown that treatment time is significant for OIIRR (13, 15, 16, 18, 20, 44–47), whereas some studies did not show any significance for treatment time and OIIRR (17, 19, 48) as found in the present study. It may be difficult to look at treatment time only, without considering other factors such as severity of the malocclusion (44), amount of tooth movement (41, 46, 47, 49, 50) and the size of the overjet (13, 20, 37), which are factors previously found to be associated with OIIRR. In the present study, the subjects were homogenous, as all the patients were Angle Class II division 2 patients and treated with Class II mechanisms without any extractions. OIIRR occurred significantly more often in patients with agenesis than patients without agenesis. It should be bared in mind that only seven patients in the present study had agenesis. However, the findings are in agreement with previous studies (10, 11, 51). One explanation may be that the innervation of the most vulnerable areas of the dentition is stressed, hence the agenesis and the higher risk of OIIRR (11, 51). Another theory is that patients with agenesis require more extensive dental rehabilitation, which often includes a long period of orthodontic treatment (10). Taurodontism was not associated with the occurrence of OIIRR in the present study. Taurodontism and OIIRR have only been sparsely investigated previously and studies disagree on whether taurodontism may be a risk factor for OIIRR (11, 52). The present study found no significant association between craniofacial morphology and OIIRR, which is in agreement with a previous study (40). One explanation for the lack of a significant difference for craniofacial morphology and OIIRR is that craniofacial morphology may not have any influence on OIIRR. Another explanation may be that all patients included in the present study had Angle Class II division 2 malocclusion, and thus a relatively homogenous anatomical character with respect to craniofacial morphology and malocclusion. 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Published: Nov 17, 2017

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