Comparison of the efficacy of tooth alignment among lingual and labial brackets: an in vitro study

Comparison of the efficacy of tooth alignment among lingual and labial brackets: an in vitro study Summary Background/objective The aim of this study was to evaluate the efficacy of tooth alignment with conventional and self-ligating labial and lingual orthodontic bracket systems. Materials/methods We tested labial brackets (0.022″ slot size) and lingual brackets (0.018″ slot size). The labial brackets were: (i) regular twin brackets (GAC-Twin [Dentsply]), (ii) passive self-ligating brackets including (Damon-Q® [ORMCO]; Ortho classic H4™ [Orthoclassic]; FLI®SL [RMO]), and (iii) active self-ligating brackets (GAC In-Ovation®C [DENTSPLY] and SPEED™[Strite]). The lingual brackets included (i) twin bracket systems (Incognito [3M] and Joy™ [Adenta]), (ii) passive self-ligating bracket system (GAC In-Ovation®LM™ [Dentsply]), and (iii) active self-ligating bracket system (Evolution SLT [Adenta]). The tested wires were Thermalloy-NiTi 0.013″ and 0.014″ (RMO). The archwires were tied to the regular twin brackets with stainless steel ligatures 0.010″ (RMO). The malocclusion simulated a displaced maxillary central incisor in the x-axis (2 mm gingivally) and in the z-axis (2 mm labially). Results The results showed that lingual brackets are less efficient in aligning teeth when compared with labial brackets in general. The vertical correction achieved by labial bracket systems ranged from 72 to 95 per cent with 13″ Thermalloy wires and from 70 to 87 per cent with 14″ Thermalloy wires. In contrast, the achieved corrections by lingual brackets with 13″ Thermalloy wires ranged between 25–44 per cent and 29–52 per cent for the 14” Thermalloy wires. The anteroposterior correction achieved by labial brackets ranged between 83 and 138 per cent for the 13″ Thermalloy and between 82 and 129 per cent for the 14″ Thermalloy wires. On the other hand, lingual brackets corrections ranged between 12 and 40 per cent for the 13″ Thermalloy wires and between 30 and 45 per cent for the 14″ Thermalloy wires. Limitation This is a lab-based study with different labial and lingual bracket slot sizes (however they are the commonly used ones in clinical orthodontics) and study did not consider saliva, periodontal ligament, mastication and other oral functions. Conclusions The effectiveness of lingual brackets in correcting vertical and anteroposterior displacement achieved during the initial alignment phase of orthodontic treatment is lower than that of the effectiveness of labial brackets. Introduction Over the recent years, the number of individuals receiving orthodontic treatment have shifted from essentially children to a notably increased number of adults. The advent of aesthetic appliances has influenced this increase in the acceptability of orthodontic care for adults partly. A high standard of an efficient orthodontic treatment is an optimum goal. The literatures have outlined different indicators of orthodontic appliance efficiency. These indicators including but not limited to the speed of tying orthodontic wires, doctor time (1), the time needed to complete alignment of crowded teeth (2), orthodontic treatment duration, or the number of visits (3, 4). The importance of treatment efficiency arises from the fact that treatment duration is a concern for many orthodontic patients who want to know for how long they will wear the braces as well as for clinicians who want to ensure efficient office management (5, 6). The lingual orthodontic bracket systems have received an increasing popularity and may represent a unique solution that does not impair the patient’s aesthetics (7). The optimum aesthetic requirement of orthodontic appliance may be achieved by the use of lingual appliances (7, 8). Lingual orthodontic brackets have been introduced in the 1970s (9, 10). A fully customized lingual orthodontic appliance was introduced afterwards (11), and its results have been shown to be comparable to those of labial and regular lingual appliances (12). However, there is evidence that the teeth lingual surfaces are more resistant to dental caries compared to labial surfaces (13, 14). The introduction of labial and lingual self-ligating brackets was initially aimed to provide biologically acceptable orthodontic forces and/or to provide more controlled tooth movement compared to those provided with conventional orthodontic bracket systems (15–18). Many studies have shown a significant decrease in ligation time of the labial self-ligating brackets than wire ligation of conventional brackets (19–21). On the other hand, it has been reported that lingual self-ligating brackets may decrease the chairside time needed to change archwires more than that needed to change archwires with labial self-ligating appliance (22). In addition, lingual technique has been considered to be a difficult technique, as it requires special experience and achieving first- and third-order tooth movements is very difficult due to the difference of the anatomy of the lingual surfaces (23), lingual appliances require more chair-side time than with labial bracket systems and in general, longer treatment times are experienced with lingual orthodontic systems than with labial orthodontic brackets systems (24). The main problem in the biomechanics of lingual orthodontics is the short interbracket distance (25). This means that for any wire, the smaller the interbracket distance, the stiffer the wire. Other problems related to finishing orthodontic cases using lingual appliances have also been reported to be dealt with by improving bracket positioning, customized archwires and minimizing play between archwire and bracket slot (26). Superelastic NiTi wires have gained rapid popularity for use in orthodontics and are reported to be more effective and efficient than any alternative wires in the initial treatment phase (27). Theses wires can take advantage of unique properties, including large elastic deflections, relatively constant forces, and thermal or shape-memory effects (27–29). The purpose of this study was to evaluate the effectiveness of the correction of vertical and anteroposterior orthodontic tooth malposition by different conventional and self-ligating labial as well as lingual bracket systems. Material and methods The tested labial orthodontic brackets included: (1) active SL (GAC In Ovation®C, Dentsply; Speed™, Strite), (2) passive SL brackets (Damon® [ORMCO]; FLI®SL [RMO]; Ortho Classic H4™ [Ortho Classic] and conventional brackets (GAC Twin [DENTSPLY]). In the case of the conventional brackets, the archwires were tied with stainless steel ligatures 0.010-in (RMO). The lingual brackets included: active self-ligating (Evolution SLT, [Adenta]), passive self-ligating (GAC In-Ovation®LM™, [DENTSPLY]), and conventional brackets (Incognito, [3M]; Joy™, [Adenta]). The tested lingual brackets incorporate 0.018-in slot size. This is the available slot size in lingual orthodontic brackets. The labial brackets have 0.022-in slot size. This is the most commonly used labial bracket slot size in the USA, UK (30), and many other countries. Two Thermalloy NiTi archwires 0.013-in and 0.014-in were used for all brackets. The transition temperature range (TTR) of thermalloy is 80–90° F (26.7–32.2°C). Regular archwires were applied for labial brackets and mushroom shaped lingual archwires were used with the lingual brackets (RMO, Denver, Colorado). Table 1 shows description and the mesiodistal widths of the tested brackets in this study. Table 1. Study design with reference to materials used. Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation View Large Table 1. Study design with reference to materials used. Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation View Large Acrylic resin models (Palavit G 4004; Heraeus Kulzer, Hanau, Germany) were fabricated from a self-cured acrylic resin (Frasaco, Tettnang, Germany) of a normal maxillary arch. Then, the upper right central incisor was eliminated from each model to allow for the use of a sensor of the custom made orthodontic measurement and simulation system (OMSS) (31, 32). The OMSS consists of two sensors that can measure forces and moments in the three dimensions (31, 32). These two sensors are incorporated on motor-driven stages that can be adjusted to move in three planes of space. The experiment was controlled via commands that were provided by a personal computer to the OMSS. The setup for measurements has been described before (33, 34). The simulated tooth movement was performed to correct the displaced upper central incisor and the forces were measured in each of the vertical and anteroposterior positions. In addition, a calculation of the tooth movement vector was mathematically analyzed considering the centre of resistance of the upper central incisor tooth to be located at 10 mm apically from the centre of the brackets and was located 4.5 mm palatally from the point of application of force (31). The tooth movement vector was divided into 0.01 mm (0.01 degrees) increments that were achieved by the motor-driven stages. Tooth movement was then stopped at the end of each increment, and the force was then remeasured. This cycle was repeated up to 200 times or when the central incisor position was corrected where no force or moment was detected at the bracket sensor. The proportion of the performed movement to the initial malposition was considered as the efficacy of each archwire/bracket combination to correct the misplaced central incisor (33). Statistical analysis was performed utilizing Mann–Whitney U test to evaluate any statistical significant differences between each wire/bracket combinations as well as Bonferroni correction was used to detect difference for multiple analyses. Significance difference was set at 0.05. Statistical analysis was performed using the statistics package SPSS® for Windows (Version 22, IBM, Armonk, New York) and graphics and statistics software Excel Version 2007 (Microsoft, Redmond, Washington). Results All the achieved corrections of the upper incisor malposition by the 0.013″ and 0.014″ Thermalloy NiTi wires with the labial and lingual brackets are presented in Figure 1A and B. The labial brackets show higher corrections in both the intrusion/extrusion and protrusion/retrusion directions compared to those obtained by lingual brackets. The vertical corrections obtained by labial brackets ranged between 72 and 95 per cent for the 0.013″ Thermalloy wires and between 70 and 87 per cent for 0.014″ Thermalloy wires. The protrusion/retrusion corrections obtained with labial brackets ranged between 83 and 138 per cent with 0.013″ Thermalloy wires and ranged between 82 and 129 per cent with 0.014″ Thermalloy wires. On the other hand, the intrusion/extrusion correction by lingual brackets ranged between 25 and 44 per cent and protrusion/retrusion correction ranged between 12 and 40 per cent with 0.013″ Thermalloy wires. Also the intrusion/extrusion correction ranged between 29 and 52 per cent for 0.013″ Thermalloy wires and between 30 and 45 per cent, with 0.014″ Thermalloy. Figure 1. View largeDownload slide Maximum correction for labial and lingual brackets: (A) in the x-axis direction (incisogingival movement), and (B) in the z-axis direction (labiolingual movement). Figure 1. View largeDownload slide Maximum correction for labial and lingual brackets: (A) in the x-axis direction (incisogingival movement), and (B) in the z-axis direction (labiolingual movement). In the vertical direction (x-axis, intrusion/extrusion), the largest corrections (Table 2) were observed with SPEED bracket system with 0.013″ Thermalloy wires (95%) and with both SPEED and Ortho Classic bracket systems 87 per cent with 0.014″ Thermalloy wires, respectively. The lowest corrections in the intrusion/extrusion direction were obtained by lingual brackets Evolution SLT 25 per cent with 0.013″ and 29 per cent with 0.014″ Thermalloy wires. Table 2. Descriptive statistics of the mean correction (mm and percent) in the x- and z axes. Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Mean ± standard deviation values in each column with the superscript letters are not significantly different at P < 0.05. aGAC In-Ovation®C, bSPEED, cDamon-Q, dFLI®SL, eOrtho Classic, fGAC Twin, gGAC In-Ovation®LM, hEvolution, iIncognito, and jJoy. View Large Table 2. Descriptive statistics of the mean correction (mm and percent) in the x- and z axes. Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Mean ± standard deviation values in each column with the superscript letters are not significantly different at P < 0.05. aGAC In-Ovation®C, bSPEED, cDamon-Q, dFLI®SL, eOrtho Classic, fGAC Twin, gGAC In-Ovation®LM, hEvolution, iIncognito, and jJoy. View Large In the protrusion/retrusion direction, the largest corrections were obtained by Damon-Q 138 per cent with 0.013″ Thermalloy wires and 129 per cent with 0.014″ Thermalloy wires. The lowest correction in the protrusion/retrusion direction were obtained by lingual brackets GAC In-Ovation®LM 12 per cent with 0.013″ and by Incognito 35 per cent with 0.014″ Thermalloy wires. Figure 1A and B show the inconsistent differences between conventional brackets and active or passive self-ligating brackets. For both 0.013″ and 0.014″ Thermalloy in the x and z-axes, for example the correction with Damon was 138 per cent compared to 127 per cent with SPEED in the z-axis with 0.013″ Thermalloy. On the other hand, some passive SL brackets showed less correction than active labial SL brackets (e.g. the correction with FLI®SL was 96 per cent compared to SPEED was 127 per cent in the z axis with 0.013″ Thermalloy). In addition, some active SL brackets showed less correction than some conventional brackets (e.g. the correction with Evolution SLT was 39 per cent compared to 45 per cent with Joy with 0.014″ Thermaloy in the z-axis). Also, there were insignificant differences (P > 0.05) between some active self-ligating (GAC In Ovation®C) or passive self-ligating brackets (FLI®SL) and conventional brackets (GAC Twin) (Table 2). Also, SPEED and passive self-ligating brackets (Ortho Classic) showed significant differences (P < 0.05) compared with another self-ligating (GAC In Ovation®C/Damon-Q) or conventional brackets (GAC Twin). Also, lingual bracket systems showed similar inconsistencies. Discussion Although the in vitro study does not simulate the oral cavity environment in all aspects, in vitro studies can provide proof of principle in today’s epoch of evidence-based dentistry. The OMSS, made it possible to analyze orthodontic tooth movement dynamically (31). In this study, we evaluated the differences between the amount of tooth alignment achieved by labial and lingual brackets during the initial levelling phase with 0.013″ and 0.014″ NiTi Thermalloy wires with different active self-ligating, passive self-ligating and conventional brackets. The commonly used wires in levelling and alignment phases is either 0.013″ or 0.014″ NiTi wires. It is to be noted that also some clinicians may start orthodontic levelling and alignment phase using 0.016 NiTi wires, depending on the severity of crowding/archwire displacement. In our study, we have utilized 0.013″ and 0.014″ Thermalloy wires, which to our best knowledge are the commonly utilized initial levelling wires. Labial brackets showed significantly increased efficacy of alignment correction than what was achieved with lingual brackets. Both conventional and self-ligating (passive or active) brackets showed higher correction compared to lingual brackets. This could be due to the smaller the wire lengths in between brackets in the case of lingual brackets relative to those of the labial brackets in general (Table 1). Reducing the interbracket length of the wires decreases the archwire springiness and its range of action (35). According to Burstone (27) when the interbracket distance with lingual appliance reduced from 8 to 4 mm the stiffness is inversely proportional to L3. Therefore, the stiffness of the lingual to labial is 83/43 = 8. That means, a 50 per cent reduction in wire length leads to 800 per cent the Stiffness (27). In addition, this may be due to the bracket slot dimension difference (0.022″ for the labial brackets and 0.018″ for the lingual brackets). It is known that with a small bracket slot, it is expected to have the less play between the archwire and the bracket and higher forces are expected with lingual brackets than with labial brackets. We have selected the lingual brackets (0.018″ slot) and labial brackets (0.022″ slot) as they are the most commonly used brackets slot sizes in the USA, UK (30) as well as expected to be the same in other countries. A previous study measured the efficiency with different self-ligating and conventional labial brackets and reported that the tooth alignment occurred because of the interaction between the bracket design, bracket type, and wire type. That study reported that up to 95 per cent alignment was produced with archwires such as 0.012″ Orthonol, 0.012″ Thermalloy, or 0.0155″ coaxial archwires (33). Non-significant differences (P > 0.05) were observed in the correction of malaligned central incisor in both the x- and z-axes between some active self-ligating (GAC In Ovation®C, Evolution SLT) or passive self-ligating (FLI®SL, GAC In-Ovation®LM) and conventional brackets (GAC Twin, Joy) for both 0.013″ and 0.014″ Thermalloy with labial and lingual brackets (Table 2). Another active self-ligating (SPEED) and passive self-ligating brackets (Ortho Classic) showed significant differences (P < 0.05) compared with another self-ligating (GAC In Ovation®C/Damon-Q) or conventional brackets (GAC Twin). These differences could be due to the design, material of each bracket as well as the difference in the interbracket distances between these brackets. These results are comparable with Fansa et al. (36) who measured the efficiency of alignment of the upper central incisor with different archwires (BioStarter® 0.012″, 0.016″; Titanol® Low Force 0.016″ × 0.016″ and 0.016″ × 0.022″) with several self-ligating and conventional brackets as well. They found that the type of ligation, whether self-ligating (active or passive) or conventional labial brackets play a secondary role in incisor position correction. They found over-correction or nearly complete correction of anteroposterior correction was related to torque movement in the range of 7.5 to 12 degrees (36). We have also observed over-correction in our study with some labial brackets that could be due to the fact that the forces were applied eccentrically to the centre of resistance, which of course is due to the labial location of the brackets to the centre of resistance of the central incisor. As the forces have an extrusive effect, a lingual crown torque is generated in combination with the lever arm and the bracket apparently displays larger movement and overcorrection. When the archwire diameter had increased from 0.013″ to 0.014″, it did not increase in the amount of correction achieved for either lingual or labial brackets as it might be expected (Table 3). The maximum observed increase in correction of the malaligned upper incisor with the 0.014″ archwires was 22 per cent compared to the 0.013″ archwires (Table 3). On the other hand, a maximum of 10 per cent decrease in the alignment correction was observed with increasing the archwire diameter from 0.013″ to 0.014″. These results are in agreement with those reported by Montasser et al. (37). They found that increasing the diameter of the archwire from 0.014″ to 0.016″ did not increase in the amount of incisor position correction. This could be due to the nature of the in vitro system where only the wire and one tooth can move, the bigger the wire the more stiff it is and therefore the more prone to produce a notch at the corners of the bracket adjacent to the incisor bracket displaced, reducing the efficacy of the movement. This could be also explained by the higher friction in the adjacent brackets with higher archwire diameters. Additionally, increasing the wire dimension could have limited the wire play in the bracket slots, which may have produced a minor difference affecting the efficacy of tooth movement. Future studies shall be planned to evaluate efficacy and force levels exerted by similar archwires in combination with labial versus lingual brackets with same (0.018″) slot sizes. Table 3. Correction change with the increase of the wire cross section (from 0.013″ to 0.014″) in the incisogingival (x-axis) and labiolingual (z-axis). Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 View Large Table 3. Correction change with the increase of the wire cross section (from 0.013″ to 0.014″) in the incisogingival (x-axis) and labiolingual (z-axis). Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 View Large Conclusion 1. This study showed that the lingual brackets were less efficient in correcting initial tooth alignment than in the labial brackets. 2. No relevant differences were found for the efficacy of tooth alignment correction between active or passive self-ligating brackets and conventional brackets for either labial or lingual brackets. 3. Increasing the archwire diameter from 0.013″ to 0.014″ did not increase the correction of malaligned central incisor either lingual or labial brackets. Clinical relevance The labial brackets are more efficient in tooth alignment at the initial stages than the lingual brackets. However, additional measures could be done to improve the efficacy of tooth misalignment with lingual appliances, i.e. to enlarge the interbracket distance to increase wire flexibility. In addition, highly flexible nickel titanium archwires would be recommended especially with lingual appliances. The authors would like to thank Rocky Mountain Orthodontics, ORMCO, Ortho Classic, Dentsply, 3M, Adenta, and Strite for supplying the materials for this research. Funding This study was supported in part by the Alexander von Humboldt Foundation Senior Research Award Received by Dr Tarek El-Bialy. Conflict of Interest The authors declare that there is no conflict of interest with any of the companies that manufactured, produced, or donated any of the materials that have been investigated in this study. References 1. Turnbull , N.R. and Birnie , D.J . ( 2007 ) Treatment efficiency of conventional vs self-ligating brackets: effects of archwire size and material . American Journal of Orthodontics and Dentofacial Orthopedics , 131 , 395 – 399 . Google Scholar CrossRef Search ADS PubMed 2. Scott , P. , DiBiase , A.T. , Sherriff , M. and Cobourne , M.T . ( 2008 ) Alignment efficiency of Damon3 self-ligating and conventional orthodontic bracket systems: a randomized clinical trial . American Journal of Orthodontics and Dentofacial Orthopedics , 134 , 470.e1 – 470.e8 . 3. Fleming , P.S. , DiBiase , A.T. and Lee , R.T . ( 2010 ) Randomized clinical trial of orthodontic treatment efficiency with self-ligating and conventional fixed orthodontic appliances . 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Alexander , C.M. , Alexander , R.G. , Gorman , J.C. , Hilgers , J.J. , Kurz , C. , Scholz , R.P. and Smith , J.R . ( 1982 ) Lingual orthodontics. A status report . Journal of Clinical Orthodontics , 16 , 255 – 262 . Google Scholar PubMed 10. Fujita , K . ( 1979 ) New orthodontic treatment with lingual bracket mushroom arch wire appliance . American Journal of Orthodontics , 76 , 657 – 675 . Google Scholar CrossRef Search ADS PubMed 11. Grauer , D. and Proffit , W.R . ( 2011 ) Accuracy in tooth positioning with a fully customized lingual orthodontic appliance . American Journal of Orthodontics and Dentofacial Orthopedics , 140 , 433 – 443 . Google Scholar CrossRef Search ADS PubMed 12. Smith , J.R. , Gorman , J.C. , Kurz , C. and Dunn , R.M . ( 1986 ) Keys to success in lingual therapy. Part 2 . Journal of Clinical Orthodontics , 20 , 330 – 340 . Google Scholar PubMed 13. Wiechmann , D. , Klang , E. , Helms , H.J. and Knösel , M . ( 2015 ) Lingual appliances reduce the incidence of white spot lesions during orthodontic multibracket treatment . American Journal of Orthodontics and Dentofacial Orthopedics , 148 , 414 – 422 . Google Scholar CrossRef Search ADS PubMed 14. van der Veen , M.H. , Attin , R. , Schwestka-Polly , R. and Wiechmann , D . ( 2010 ) Caries outcomes after orthodontic treatment with fixed appliances: do lingual brackets make a difference ? European Journal of Oral Sciences , 118 , 298 – 303 . Google Scholar CrossRef Search ADS PubMed 15. Cacciafesta , V. and Sfondrini , M.F . ( 2010 ) Correction of horizontal and vertical discrepancies with a new interactive self-ligating bracket system: the Quick system . World Journal of Orthodontics , 11 , 404 – 412 . Google Scholar PubMed 16. Chen , S.S. , Greenlee , G.M. , Kim , J.E. , Smith , C.L. and Huang , G.J . ( 2010 ) Systematic review of self-ligating brackets . American Journal of Orthodontics and Dentofacial Orthopedics , 137 , 726.e1 – 726.e18; discussion 726 . 17. Fleming , P.S. and Johal , A . ( 2010 ) Self-ligating brackets in orthodontics. A systematic review . The Angle Orthodontist , 80 , 575 – 584 . Google Scholar CrossRef Search ADS PubMed 18. Eberting , J.J. , Straja , S.R. and Tuncay , O.C . ( 2001 ) Treatment time, outcome, and patient satisfaction comparisons of Damon and conventional brackets . Clinical Orthodontics and Research , 4 , 228 – 234 . Google Scholar CrossRef Search ADS PubMed 19. Maijer , R. and Smith , D.C . ( 1990 ) Time savings with self-ligating brackets . Journal of Clinical Orthodontics , 24 , 29 – 31 . Google Scholar PubMed 20. Shivapuja , P.K. and Berger , J . ( 1994 ) A comparative study of conventional ligation and self-ligation bracket systems . American Journal of Orthodontics and Dentofacial Orthopedics , 106 , 472 – 480 . Google Scholar CrossRef Search ADS PubMed 21. Storey , E. and Smith , R . ( 1952 ) Force in orthodontics and its relation to tooth movement . Australian Dental Journal , 56 , 11 – 8 . 22. Cacciafesta , V . ( 2013 ) The 2D lingual appliance system . Journal of Orthodontics , 40 , S60 – S67 . Google Scholar CrossRef Search ADS PubMed 23. Nidoli , G. , Lazzati , M. , Macchi , A. and Castoldi , A . ( 1985 ) Clinico-statistical analysis of dental morphology in relation to positioning of lingual brackets . Mondo Ortodontico , 10 , 45 – 53 . Google Scholar PubMed 24. Dalessandri , D. , Lazzaroni , E. , Migliorati , M. , Piancino , M.G. , Tonni , I. and Bonetti , S . ( 2013 ) Self-ligating fully customized lingual appliance and chair-time reduction: a typodont study followed by a randomized clinical trial . European Journal of Orthodontics , 35 , 758 – 765 . Google Scholar CrossRef Search ADS PubMed 25. Romano R . ( 1998 ) Lingual Orthodontics . Hamilton, Ont., BC Decker , pp. 15, 16, 63. 26. Auluck , A . ( 2013 ) Lingual orthodontic treatment: what is the current evidence base ? Journal of Orthodontics , 40 , S27 – S33 . Google Scholar CrossRef Search ADS PubMed 27. Burstone , C.J. and Choy , K . ( 2015 ) The Biomechanical Foundational of Clinical Orthodontics . Quintessence Publishing Co., Chicago , 1st edn, pp. 477, 491 – 498 . 28. Mandall , N. , Lowe , C. , Worthington , H. , Sandler , J. , Derwent , S. , Abdi-Oskouei , M. and Ward , S . ( 2006 ) Which orthodontic archwire sequence? A randomized clinical trial . European Journal of Orthodontics , 28 , 561 – 566 . Google Scholar CrossRef Search ADS PubMed 29. Pandis , N. , Polychronopoulou , A. and Eliades , T . ( 2009 ) Alleviation of mandibular anterior crowding with copper-nickel-titanium vs nickel-titanium wires: a double-blind randomized control trial . American Journal of Orthodontics and Dentofacial Orthopedics , 136 , 152.e1 – 7;discussion 152 . 30. El-Angbawi , A.M. , Bearn , D.R. and McIntyre , G.T . ( 2014 ) Comparing the effectiveness of the 0.018-inch versus the 0.022-inch bracket slot system in orthodontic treatment: study protocol for a randomized controlled trial . Trials , 15 , 389 . Google Scholar CrossRef Search ADS PubMed 31. Drescher , D. , Bourauel , C. and Thier , M . ( 1991 ) Application of the orthodontic measurement and simulation system (OMSS) in orthodontics . European Journal of Orthodontics , 13 , 169 – 178 . Google Scholar CrossRef Search ADS PubMed 32. Bourauel , C. , Drescher , D. and Thier , M . ( 1992 ) An experimental apparatus for the simulation of three-dimensional movements in orthodontics . Journal of Biomedical Engineering , 14 , 371 – 378 . Google Scholar CrossRef Search ADS PubMed 33. Montasser , M.A. , Keilig , L. and Bourauel , C . ( 2015 ) An in vitro study into the efficacy of complex tooth alignment with conventional and self-ligating brackets . Orthodontics and Craniofacial Research , 18 , 33 – 42 . Google Scholar CrossRef Search ADS PubMed 34. Alobeid , A. , El-Bialy , T. , Khawatmi , S. , Dirk , C. , Jäger , A. and Bourauel , C . ( 2017 ) Comparison of the force levels among labial and lingual self-ligating and conventional brackets in simulated misaligned teeth . European Journal of Orthodontics , 39 , 419 – 425 . Google Scholar CrossRef Search ADS PubMed 35. Proffit , W.R. , Fields , H.W. and Sarver , D.M . ( 2013 ) Contemporary Orthodontics . 5th ed . Mosby , St Louis . pp. 328 – 667 . 36. Fansa , M. , Keilig , L. , Reimann , S. , Jäger , A. and Bourauel , C . ( 2009 ) The leveling effectiveness of self-ligating and conventional brackets for complex tooth malalignments . Journal of Orofacial Orthopedics , 70 , 285 – 296 . Google Scholar CrossRef Search ADS PubMed 37. Montasser , M.A. , Keilig , L. and Bourauel , C . ( 2016 ) Archwire diameter effect on tooth alignment with different bracket-archwire combinations . American Journal of Orthodontics and Dentofacial Orthopedics , 149 , 76 – 83 . Google Scholar CrossRef Search ADS PubMed © 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

Comparison of the efficacy of tooth alignment among lingual and labial brackets: an in vitro study

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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/cjy005
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Abstract

Summary Background/objective The aim of this study was to evaluate the efficacy of tooth alignment with conventional and self-ligating labial and lingual orthodontic bracket systems. Materials/methods We tested labial brackets (0.022″ slot size) and lingual brackets (0.018″ slot size). The labial brackets were: (i) regular twin brackets (GAC-Twin [Dentsply]), (ii) passive self-ligating brackets including (Damon-Q® [ORMCO]; Ortho classic H4™ [Orthoclassic]; FLI®SL [RMO]), and (iii) active self-ligating brackets (GAC In-Ovation®C [DENTSPLY] and SPEED™[Strite]). The lingual brackets included (i) twin bracket systems (Incognito [3M] and Joy™ [Adenta]), (ii) passive self-ligating bracket system (GAC In-Ovation®LM™ [Dentsply]), and (iii) active self-ligating bracket system (Evolution SLT [Adenta]). The tested wires were Thermalloy-NiTi 0.013″ and 0.014″ (RMO). The archwires were tied to the regular twin brackets with stainless steel ligatures 0.010″ (RMO). The malocclusion simulated a displaced maxillary central incisor in the x-axis (2 mm gingivally) and in the z-axis (2 mm labially). Results The results showed that lingual brackets are less efficient in aligning teeth when compared with labial brackets in general. The vertical correction achieved by labial bracket systems ranged from 72 to 95 per cent with 13″ Thermalloy wires and from 70 to 87 per cent with 14″ Thermalloy wires. In contrast, the achieved corrections by lingual brackets with 13″ Thermalloy wires ranged between 25–44 per cent and 29–52 per cent for the 14” Thermalloy wires. The anteroposterior correction achieved by labial brackets ranged between 83 and 138 per cent for the 13″ Thermalloy and between 82 and 129 per cent for the 14″ Thermalloy wires. On the other hand, lingual brackets corrections ranged between 12 and 40 per cent for the 13″ Thermalloy wires and between 30 and 45 per cent for the 14″ Thermalloy wires. Limitation This is a lab-based study with different labial and lingual bracket slot sizes (however they are the commonly used ones in clinical orthodontics) and study did not consider saliva, periodontal ligament, mastication and other oral functions. Conclusions The effectiveness of lingual brackets in correcting vertical and anteroposterior displacement achieved during the initial alignment phase of orthodontic treatment is lower than that of the effectiveness of labial brackets. Introduction Over the recent years, the number of individuals receiving orthodontic treatment have shifted from essentially children to a notably increased number of adults. The advent of aesthetic appliances has influenced this increase in the acceptability of orthodontic care for adults partly. A high standard of an efficient orthodontic treatment is an optimum goal. The literatures have outlined different indicators of orthodontic appliance efficiency. These indicators including but not limited to the speed of tying orthodontic wires, doctor time (1), the time needed to complete alignment of crowded teeth (2), orthodontic treatment duration, or the number of visits (3, 4). The importance of treatment efficiency arises from the fact that treatment duration is a concern for many orthodontic patients who want to know for how long they will wear the braces as well as for clinicians who want to ensure efficient office management (5, 6). The lingual orthodontic bracket systems have received an increasing popularity and may represent a unique solution that does not impair the patient’s aesthetics (7). The optimum aesthetic requirement of orthodontic appliance may be achieved by the use of lingual appliances (7, 8). Lingual orthodontic brackets have been introduced in the 1970s (9, 10). A fully customized lingual orthodontic appliance was introduced afterwards (11), and its results have been shown to be comparable to those of labial and regular lingual appliances (12). However, there is evidence that the teeth lingual surfaces are more resistant to dental caries compared to labial surfaces (13, 14). The introduction of labial and lingual self-ligating brackets was initially aimed to provide biologically acceptable orthodontic forces and/or to provide more controlled tooth movement compared to those provided with conventional orthodontic bracket systems (15–18). Many studies have shown a significant decrease in ligation time of the labial self-ligating brackets than wire ligation of conventional brackets (19–21). On the other hand, it has been reported that lingual self-ligating brackets may decrease the chairside time needed to change archwires more than that needed to change archwires with labial self-ligating appliance (22). In addition, lingual technique has been considered to be a difficult technique, as it requires special experience and achieving first- and third-order tooth movements is very difficult due to the difference of the anatomy of the lingual surfaces (23), lingual appliances require more chair-side time than with labial bracket systems and in general, longer treatment times are experienced with lingual orthodontic systems than with labial orthodontic brackets systems (24). The main problem in the biomechanics of lingual orthodontics is the short interbracket distance (25). This means that for any wire, the smaller the interbracket distance, the stiffer the wire. Other problems related to finishing orthodontic cases using lingual appliances have also been reported to be dealt with by improving bracket positioning, customized archwires and minimizing play between archwire and bracket slot (26). Superelastic NiTi wires have gained rapid popularity for use in orthodontics and are reported to be more effective and efficient than any alternative wires in the initial treatment phase (27). Theses wires can take advantage of unique properties, including large elastic deflections, relatively constant forces, and thermal or shape-memory effects (27–29). The purpose of this study was to evaluate the effectiveness of the correction of vertical and anteroposterior orthodontic tooth malposition by different conventional and self-ligating labial as well as lingual bracket systems. Material and methods The tested labial orthodontic brackets included: (1) active SL (GAC In Ovation®C, Dentsply; Speed™, Strite), (2) passive SL brackets (Damon® [ORMCO]; FLI®SL [RMO]; Ortho Classic H4™ [Ortho Classic] and conventional brackets (GAC Twin [DENTSPLY]). In the case of the conventional brackets, the archwires were tied with stainless steel ligatures 0.010-in (RMO). The lingual brackets included: active self-ligating (Evolution SLT, [Adenta]), passive self-ligating (GAC In-Ovation®LM™, [DENTSPLY]), and conventional brackets (Incognito, [3M]; Joy™, [Adenta]). The tested lingual brackets incorporate 0.018-in slot size. This is the available slot size in lingual orthodontic brackets. The labial brackets have 0.022-in slot size. This is the most commonly used labial bracket slot size in the USA, UK (30), and many other countries. Two Thermalloy NiTi archwires 0.013-in and 0.014-in were used for all brackets. The transition temperature range (TTR) of thermalloy is 80–90° F (26.7–32.2°C). Regular archwires were applied for labial brackets and mushroom shaped lingual archwires were used with the lingual brackets (RMO, Denver, Colorado). Table 1 shows description and the mesiodistal widths of the tested brackets in this study. Table 1. Study design with reference to materials used. Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation View Large Table 1. Study design with reference to materials used. Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation Bracket type Bracket width (central incisor) Bracket width (lateral incisor) Distance between central and lateral incisors’ brackets Type of ligation Type of wire Group observations (per wire) Total observations Labial brackets GAC innovation®C 2.9 mm 2.7 mm 15.2 mm Active self-ligation 0.013″ NiTi (Thermalloy) 0.014″ NiTi (Thermalloy) 5 100 SPEED 2.2 mm 2.4 mm 13.8 mm Active self-ligation Damon-Q 2.9 mm 2.8 mm 13.7 mm Passive self-ligation Fli-SL 3.3 mm 3.0 mm 13.9 mm Passive self-ligation Ortho Classic H4™ 2.7 mm 2.7 mm 16.3 mm Passive self-ligation GAC Twin 3.8 mm 3.0 mm 14.0 mm Stainless steel ligation Lingual brackets GAC In-Ovation®LM 2.2 mm 2.2 mm 10.8 mm Passive self-ligation Evolution SLT 2.4 mm 2.4 mm 10.5 mm Active self-ligation Incognito 2.4 mm 2.2 mm 10.8 mm Stainless steel ligation Joy 2.2 mm 2.2 mm 10.9 mm Stainless steel ligation View Large Acrylic resin models (Palavit G 4004; Heraeus Kulzer, Hanau, Germany) were fabricated from a self-cured acrylic resin (Frasaco, Tettnang, Germany) of a normal maxillary arch. Then, the upper right central incisor was eliminated from each model to allow for the use of a sensor of the custom made orthodontic measurement and simulation system (OMSS) (31, 32). The OMSS consists of two sensors that can measure forces and moments in the three dimensions (31, 32). These two sensors are incorporated on motor-driven stages that can be adjusted to move in three planes of space. The experiment was controlled via commands that were provided by a personal computer to the OMSS. The setup for measurements has been described before (33, 34). The simulated tooth movement was performed to correct the displaced upper central incisor and the forces were measured in each of the vertical and anteroposterior positions. In addition, a calculation of the tooth movement vector was mathematically analyzed considering the centre of resistance of the upper central incisor tooth to be located at 10 mm apically from the centre of the brackets and was located 4.5 mm palatally from the point of application of force (31). The tooth movement vector was divided into 0.01 mm (0.01 degrees) increments that were achieved by the motor-driven stages. Tooth movement was then stopped at the end of each increment, and the force was then remeasured. This cycle was repeated up to 200 times or when the central incisor position was corrected where no force or moment was detected at the bracket sensor. The proportion of the performed movement to the initial malposition was considered as the efficacy of each archwire/bracket combination to correct the misplaced central incisor (33). Statistical analysis was performed utilizing Mann–Whitney U test to evaluate any statistical significant differences between each wire/bracket combinations as well as Bonferroni correction was used to detect difference for multiple analyses. Significance difference was set at 0.05. Statistical analysis was performed using the statistics package SPSS® for Windows (Version 22, IBM, Armonk, New York) and graphics and statistics software Excel Version 2007 (Microsoft, Redmond, Washington). Results All the achieved corrections of the upper incisor malposition by the 0.013″ and 0.014″ Thermalloy NiTi wires with the labial and lingual brackets are presented in Figure 1A and B. The labial brackets show higher corrections in both the intrusion/extrusion and protrusion/retrusion directions compared to those obtained by lingual brackets. The vertical corrections obtained by labial brackets ranged between 72 and 95 per cent for the 0.013″ Thermalloy wires and between 70 and 87 per cent for 0.014″ Thermalloy wires. The protrusion/retrusion corrections obtained with labial brackets ranged between 83 and 138 per cent with 0.013″ Thermalloy wires and ranged between 82 and 129 per cent with 0.014″ Thermalloy wires. On the other hand, the intrusion/extrusion correction by lingual brackets ranged between 25 and 44 per cent and protrusion/retrusion correction ranged between 12 and 40 per cent with 0.013″ Thermalloy wires. Also the intrusion/extrusion correction ranged between 29 and 52 per cent for 0.013″ Thermalloy wires and between 30 and 45 per cent, with 0.014″ Thermalloy. Figure 1. View largeDownload slide Maximum correction for labial and lingual brackets: (A) in the x-axis direction (incisogingival movement), and (B) in the z-axis direction (labiolingual movement). Figure 1. View largeDownload slide Maximum correction for labial and lingual brackets: (A) in the x-axis direction (incisogingival movement), and (B) in the z-axis direction (labiolingual movement). In the vertical direction (x-axis, intrusion/extrusion), the largest corrections (Table 2) were observed with SPEED bracket system with 0.013″ Thermalloy wires (95%) and with both SPEED and Ortho Classic bracket systems 87 per cent with 0.014″ Thermalloy wires, respectively. The lowest corrections in the intrusion/extrusion direction were obtained by lingual brackets Evolution SLT 25 per cent with 0.013″ and 29 per cent with 0.014″ Thermalloy wires. Table 2. Descriptive statistics of the mean correction (mm and percent) in the x- and z axes. Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Mean ± standard deviation values in each column with the superscript letters are not significantly different at P < 0.05. aGAC In-Ovation®C, bSPEED, cDamon-Q, dFLI®SL, eOrtho Classic, fGAC Twin, gGAC In-Ovation®LM, hEvolution, iIncognito, and jJoy. View Large Table 2. Descriptive statistics of the mean correction (mm and percent) in the x- and z axes. Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Vestibular brackets Lingual brackets Wire type n Correction GAC In-Ovation®C SPEED Damon-Q FLI®SL Ortho Classic GAC Twin GAC In-Ovation®LM Evolution SLT Incognito Joy x-axis (intrusion/extrusion) 0.013″ 5 mm 1.4 ± 0.04c,d,f,j 1.9 ± 0.05e 1.4 ± 0.04a,d,f,j 1.5 ± 0.04a,c,f,j 1.8 ± 0.04b 1.4 ± 0.08a,c,d,j 0.5 ± 0.08h,j 0.5 ± 0.03g,j 0.8 ± 0.1j 1 ± 0.4a,c,d,f,g,h,i % 74 ± 4 95 ± 4 72 ± 4 76 ± 1 93 ± 2 74 ± 5 26 ± 4 25 ± 2 44 ± 7 40 ± 9 0.014″ 5 mm 1.3 ± 0.1c,d,f,j 1.7 ± 0.1c,d,f 1.4 ± 0.1a,b,d,f 1.5 ± 0.1a,b,c,e,f,j 1.7 ± 0.1d 1.4 ± 0.09a,b,c,d,j 0.7 ± 0.08h,i,j 0.5 ± 0.09g,i,j 0.6 ± 0.1g,h,j 1 ± 0.3a,d,f,g,h,i % 70 ± 3 87 ± 7 72 ± 11 79 ± 12 87 ± 9 74 ± 5 35 ± 4 29 ± 4 34 ± 8 52 ± 10 z-axis (protrusion/retrusion) 0.013″ 5 mm 1.6 ± 0.1f,j 2.6 ± 0.1c,e 2.7 ± 0.1b 1.9 ± 0.1f,j 2.3 ± 0.1b 1.7 ± 0.2a,d,j 0.2 ± 0.05h,j 0.3 ± 0.09g,j 0.7 ± 0.1j 1.1 ± 0.6a,d,f,h,g,i % 83 ± 14 127 ± 17 138 ± 11 96 ± 17 119 ± 6 91 ± 12 12 ± 3 16 ± 4 37 ± 6 40 ± 9 0.014″ 5 mm 1.6 ± 0.05f,j 2.4 ± 0.06e 2.6 ± 0.06 2 ± 0.05 2.3 ± 0.05b 1.6 ± 0.1a,j 0.6 ± 0.1h,i,j 0.7 ± 0.1g,i,j 0.6 ± 0.2g,h,j 1.1 ± 0.4a,f,g,h,i % 84 ± 25 121 ± 13 129 ± 7 104 ± 41 119 ± 3 82 ± 9 30 ± 6 39 ± 5 35 ± 10 45 ± 10 Mean ± standard deviation values in each column with the superscript letters are not significantly different at P < 0.05. aGAC In-Ovation®C, bSPEED, cDamon-Q, dFLI®SL, eOrtho Classic, fGAC Twin, gGAC In-Ovation®LM, hEvolution, iIncognito, and jJoy. View Large In the protrusion/retrusion direction, the largest corrections were obtained by Damon-Q 138 per cent with 0.013″ Thermalloy wires and 129 per cent with 0.014″ Thermalloy wires. The lowest correction in the protrusion/retrusion direction were obtained by lingual brackets GAC In-Ovation®LM 12 per cent with 0.013″ and by Incognito 35 per cent with 0.014″ Thermalloy wires. Figure 1A and B show the inconsistent differences between conventional brackets and active or passive self-ligating brackets. For both 0.013″ and 0.014″ Thermalloy in the x and z-axes, for example the correction with Damon was 138 per cent compared to 127 per cent with SPEED in the z-axis with 0.013″ Thermalloy. On the other hand, some passive SL brackets showed less correction than active labial SL brackets (e.g. the correction with FLI®SL was 96 per cent compared to SPEED was 127 per cent in the z axis with 0.013″ Thermalloy). In addition, some active SL brackets showed less correction than some conventional brackets (e.g. the correction with Evolution SLT was 39 per cent compared to 45 per cent with Joy with 0.014″ Thermaloy in the z-axis). Also, there were insignificant differences (P > 0.05) between some active self-ligating (GAC In Ovation®C) or passive self-ligating brackets (FLI®SL) and conventional brackets (GAC Twin) (Table 2). Also, SPEED and passive self-ligating brackets (Ortho Classic) showed significant differences (P < 0.05) compared with another self-ligating (GAC In Ovation®C/Damon-Q) or conventional brackets (GAC Twin). Also, lingual bracket systems showed similar inconsistencies. Discussion Although the in vitro study does not simulate the oral cavity environment in all aspects, in vitro studies can provide proof of principle in today’s epoch of evidence-based dentistry. The OMSS, made it possible to analyze orthodontic tooth movement dynamically (31). In this study, we evaluated the differences between the amount of tooth alignment achieved by labial and lingual brackets during the initial levelling phase with 0.013″ and 0.014″ NiTi Thermalloy wires with different active self-ligating, passive self-ligating and conventional brackets. The commonly used wires in levelling and alignment phases is either 0.013″ or 0.014″ NiTi wires. It is to be noted that also some clinicians may start orthodontic levelling and alignment phase using 0.016 NiTi wires, depending on the severity of crowding/archwire displacement. In our study, we have utilized 0.013″ and 0.014″ Thermalloy wires, which to our best knowledge are the commonly utilized initial levelling wires. Labial brackets showed significantly increased efficacy of alignment correction than what was achieved with lingual brackets. Both conventional and self-ligating (passive or active) brackets showed higher correction compared to lingual brackets. This could be due to the smaller the wire lengths in between brackets in the case of lingual brackets relative to those of the labial brackets in general (Table 1). Reducing the interbracket length of the wires decreases the archwire springiness and its range of action (35). According to Burstone (27) when the interbracket distance with lingual appliance reduced from 8 to 4 mm the stiffness is inversely proportional to L3. Therefore, the stiffness of the lingual to labial is 83/43 = 8. That means, a 50 per cent reduction in wire length leads to 800 per cent the Stiffness (27). In addition, this may be due to the bracket slot dimension difference (0.022″ for the labial brackets and 0.018″ for the lingual brackets). It is known that with a small bracket slot, it is expected to have the less play between the archwire and the bracket and higher forces are expected with lingual brackets than with labial brackets. We have selected the lingual brackets (0.018″ slot) and labial brackets (0.022″ slot) as they are the most commonly used brackets slot sizes in the USA, UK (30) as well as expected to be the same in other countries. A previous study measured the efficiency with different self-ligating and conventional labial brackets and reported that the tooth alignment occurred because of the interaction between the bracket design, bracket type, and wire type. That study reported that up to 95 per cent alignment was produced with archwires such as 0.012″ Orthonol, 0.012″ Thermalloy, or 0.0155″ coaxial archwires (33). Non-significant differences (P > 0.05) were observed in the correction of malaligned central incisor in both the x- and z-axes between some active self-ligating (GAC In Ovation®C, Evolution SLT) or passive self-ligating (FLI®SL, GAC In-Ovation®LM) and conventional brackets (GAC Twin, Joy) for both 0.013″ and 0.014″ Thermalloy with labial and lingual brackets (Table 2). Another active self-ligating (SPEED) and passive self-ligating brackets (Ortho Classic) showed significant differences (P < 0.05) compared with another self-ligating (GAC In Ovation®C/Damon-Q) or conventional brackets (GAC Twin). These differences could be due to the design, material of each bracket as well as the difference in the interbracket distances between these brackets. These results are comparable with Fansa et al. (36) who measured the efficiency of alignment of the upper central incisor with different archwires (BioStarter® 0.012″, 0.016″; Titanol® Low Force 0.016″ × 0.016″ and 0.016″ × 0.022″) with several self-ligating and conventional brackets as well. They found that the type of ligation, whether self-ligating (active or passive) or conventional labial brackets play a secondary role in incisor position correction. They found over-correction or nearly complete correction of anteroposterior correction was related to torque movement in the range of 7.5 to 12 degrees (36). We have also observed over-correction in our study with some labial brackets that could be due to the fact that the forces were applied eccentrically to the centre of resistance, which of course is due to the labial location of the brackets to the centre of resistance of the central incisor. As the forces have an extrusive effect, a lingual crown torque is generated in combination with the lever arm and the bracket apparently displays larger movement and overcorrection. When the archwire diameter had increased from 0.013″ to 0.014″, it did not increase in the amount of correction achieved for either lingual or labial brackets as it might be expected (Table 3). The maximum observed increase in correction of the malaligned upper incisor with the 0.014″ archwires was 22 per cent compared to the 0.013″ archwires (Table 3). On the other hand, a maximum of 10 per cent decrease in the alignment correction was observed with increasing the archwire diameter from 0.013″ to 0.014″. These results are in agreement with those reported by Montasser et al. (37). They found that increasing the diameter of the archwire from 0.014″ to 0.016″ did not increase in the amount of incisor position correction. This could be due to the nature of the in vitro system where only the wire and one tooth can move, the bigger the wire the more stiff it is and therefore the more prone to produce a notch at the corners of the bracket adjacent to the incisor bracket displaced, reducing the efficacy of the movement. This could be also explained by the higher friction in the adjacent brackets with higher archwire diameters. Additionally, increasing the wire dimension could have limited the wire play in the bracket slots, which may have produced a minor difference affecting the efficacy of tooth movement. Future studies shall be planned to evaluate efficacy and force levels exerted by similar archwires in combination with labial versus lingual brackets with same (0.018″) slot sizes. Table 3. Correction change with the increase of the wire cross section (from 0.013″ to 0.014″) in the incisogingival (x-axis) and labiolingual (z-axis). Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 View Large Table 3. Correction change with the increase of the wire cross section (from 0.013″ to 0.014″) in the incisogingival (x-axis) and labiolingual (z-axis). Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 Bracket type Vestibular brackets Lingual brackets GAC in-Ovation®C SPEED Damon-Q FLI®SL Ortho classic GAC twin GAC in-Ovation®LM Evolution SLT Incognito Joy Correction (x-axis) Change (%) −4 −6 −8 +2.5 −6 0 +10 +4 −10 +12 Correction (z-axis) Change (%) +2 −9 0 +8 −1 −9 +18 +22 −3 +6 View Large Conclusion 1. This study showed that the lingual brackets were less efficient in correcting initial tooth alignment than in the labial brackets. 2. No relevant differences were found for the efficacy of tooth alignment correction between active or passive self-ligating brackets and conventional brackets for either labial or lingual brackets. 3. Increasing the archwire diameter from 0.013″ to 0.014″ did not increase the correction of malaligned central incisor either lingual or labial brackets. Clinical relevance The labial brackets are more efficient in tooth alignment at the initial stages than the lingual brackets. However, additional measures could be done to improve the efficacy of tooth misalignment with lingual appliances, i.e. to enlarge the interbracket distance to increase wire flexibility. In addition, highly flexible nickel titanium archwires would be recommended especially with lingual appliances. The authors would like to thank Rocky Mountain Orthodontics, ORMCO, Ortho Classic, Dentsply, 3M, Adenta, and Strite for supplying the materials for this research. Funding This study was supported in part by the Alexander von Humboldt Foundation Senior Research Award Received by Dr Tarek El-Bialy. 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Journal

The European Journal of OrthodonticsOxford University Press

Published: Mar 13, 2018

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