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Summary Objectives Interproximal enamel reduction (IPR) is routinely used in orthodontics to generate small to moderate amounts of space within the dental arch. Aim of this ex vivo study was to evaluate the effect of two different IPR systems on the enamel surface’s waviness, roughness, and elemental composition after 6 months of intraoral exposure. Materials and methods Fifteen orthodontic extraction patients were included in the present study. The 39 healthy premolars, which were scheduled to be extracted, were subjected to IPR at least 6 months before their extraction. IPR was performed on their mesial side with two different methods: (1) instrumented method with the Ortho-Strips system (on handpiece) and (2) manually with the Intensiv ProxoStrip (strips)—each with four different grits for contouring, finishing, and polishing. The distal side of each premolar served as its own internal control. Treated and untreated tooth surfaces were evaluated by optical profilometry, Raman, and scanning electron microscope/X-ray energy-dispersive (EDX) analyses. Data were analysed with descriptive statistics and generalized linear models at alpha = 5%. Results Both IPR methods significantly reduced the waviness of the enamel surface (P Conclusions Both stripping systems led to a flatter but rougher enamel surface. Further polishing is needed to restore the initial enamel smoothness. The elemental composition of the stripped enamel returns to the baseline level after 6 months of intraoral exposure.

Summary Background Orthodontic patients wearing fixed appliances are susceptible to traumatic dental injuries during contact-sport. This laboratory study investigated the protective qualities of orthodontic mouthguards using impact-testing to a typodont fitted with a fixed appliance through peak load transfer and retention of the mouthguard. Methods Seven orthodontic mouthguards [three custom-made (Medium-CM, Heavy-CM, Heavy-pro-CM); three commercially-available mouth-formed (Shock-Doctor® Ultra Braces, Opro® Ortho-Gold Braces, Opro® Ortho-Bronze Braces) and a Shock-Doctor® Instant-Fit] were fitted to a maxillary arch typodont bonded with a fixed appliance and impact-tested using 0.5 or 1 Joule (J) energy via hockey-ball, cricket-ball or steel-ball projectile. A load-cell recorded peak load transfer through mouthguard to typodont with retention scored in a binary manner dependent upon any displacement following impact. Differences across mouthguards were calculated with ANOVA or Kruskal–Wallis test for normal and non-normal data, respectively. Post hoc comparisons across mouthguards were conducted via Dunnett's test with Sidak correction. Results Only the three custom-made and Opro® Ortho-Gold Braces were not displaced by impact-testing. For these, Opro® Ortho-Gold Braces transferred the smallest load for 3/6 impact-tests, followed by Medium-CM. Heavy-pro-CM performed poorly, ranking penultimate or worst for all impact-tests. Significant differences were found between mouthguards for cricket-ball and steel-ball set-ups. The Opro® Ortho-Gold Braces performed better than the Heavy and Heavy-pro-CM for 0.5 J cricket-ball impact-test (P < 0.05), whilst Medium-CM performed better than Heavy-pro-CM. For 1 J cricket-ball, there were significant differences between Medium-CM and Heavy-pro-CM (P < 0.05). For 0.5 J steel-ball, the Medium-CM performed significantly better than both Heavy-pro-CM and Opro® Ortho-Gold Braces (P < 0.05), whilst Heavy-CM performed better than the Heavy-pro-CM (P < 0.05). For the 1 J steel-ball, Medium and Heavy-CM performed better than Opro® Ortho-Gold Braces (P < 0.05). Conclusions Opro® Ortho-Gold and Medium-CM mouthguards offer the best protection for low-impact sports, whilst Medium or Heavy-CM mouthguards are recommended for high-impact sport.

Summary Objective To investigate alterations in the mechanical properties of in-house three-dimensional (3D) printed orthodontic aligners after intraoral ageing. Materials and methods Sixteen 3D-printed aligners (TC-85DAC resin, Graphy, Seoul, Korea) were used for the purpose of the study, which were divided into 10 control (not used) aligners and 6 materials retrieved from 4 patients after 1-week service (retrieved group). Samples from the control group were analysed by attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy. Samples from control/retrieved groups were embedded resin and subjected to instrumented indentation testing (IIT) to record force–indentation depth curves, calculating the following (as per ISO 14577-1, 2002 standard): Martens hardness (HM), indentation modulus (EIT), and elastic index (ηIT), and the indentation relaxation index (RIT). Differences between control and retrieved 3D-printed aligners were checked with Mann–Whitney/t-tests at an alpha = 5%. Results ATR-FTIR analysis showed that aligners were made of a vinyl ester–urethane material. The results of the IIT testing were: HM (control: median 91.5 N/mm2, interquartile range [IQR] 88.0–93.0/as-retrieved: median 90.5 N/mm2, IQR 89.0–93.0); EIT (control, mean 2616.3 MPa, standard deviation [SD] 107.0 MPa/retrieved, mean 2673.2 MPa, SD 149.4 MPa); ηIT (control: median 28.6%, IQR 28.2–30.9%/as-retrieved: median 29.0%, IQR 28.7–29.2%); and RIT (control: median 45.5%, IQR 43.0–47.0%/as-retrieved: median 45.1%, IQR 45.0–45.3%). No differences between as-retrieved and control aligners were found for any of the mechanical properties tested (P > 0.05 in all instances). Conclusion The mechanical properties of the in-house 3D-printed aligners tested were not affected after 1 week in service period.

Summary Objective To assess three rapid maxillary expansion (RME) appliances in nasal ventilation. Trial design Three-arm parallel randomized clinical trial. Methods Sixty-six growing subjects (10–16 years old) needing RME as part of their orthodontic treatment were randomly allocated (1:1:1 ratio) to three groups of 22 patients receiving Hyrax (H), Hybrid-Hyrax (HH), or Keles keyless expander (K). The primary outcome of nasal ventilation (pressure and velocity) and secondary outcomes (skeletal, dental, soft tissue, and nasal obstruction changes) were blindly assessed on the initial (T0) and final (T1, 6 months at appliance removal) cone-beam computed tomography (CBCT) data by applying computational fluid dynamics (CFD) method. Differences across groups were assessed with crude and adjusted for baseline values and confounders (gender, age, skeletal maturation, expansion amount, mucosal/adenoid hypertrophy, nasal septum deviation) regression models with alpha = 5%. Results Fifty-four patients were analysed (19H, 21HH, 14K). RME reduced both nasal pressure (H: −45.8%, HH: −75.5%, K: −63.2%) and velocity (H: −30%, HH: −58.5%, K: −35%) accompanied with nasal obstruction resolution (H: 26%, HH: 62%, K: 50%). Regressions accounting for baseline severity indicated HH expander performing better in terms of post-expansion maximum velocity (P = 0.03) and nasal obstruction resolution (P = 0.04), which was robust to confounders. Mucosal/adenoid hypertrophy and nasal septum deviation changes were variable, minimal, and similar across groups. The HH resulted in significantly greater increase in the nasal cross-sectional area (62.3%), anterior (14.6%), and posterior (10.5%) nasal widths. Nasal obstruction resolution was more probable among younger (P = 0.04), skeletally immature (P = 0.03), and male patients (P = 0.02) without pre-treatment mucosal hypertrophy (P = 0.04), while HH was associated with marginal greater probability for obstruction resolution. Conclusions RME resulted in improvement of nasal skeletal parameters and simulated ventilation with the former being in favour of the HH and the latter not showing significant differences among the three appliances. Limitation Attrition in the K group due to blocked activation rods possibly leading to limited sample to identify any existing group differences. Harms Replacement of blocked Keles expanders for finalizing treatment. Protocol The protocol was not published before the trial commencement. Registration Australian and New Zealand Clinical Trial Registry; ACTRN12617001136392.

Summary Introduction This prospective clinical cohort study investigated the potential influence of obesity on orthodontic treatment outcome. Methods A prospective cohort of adolescent patients undergoing routine fixed appliance treatment were recruited into normal-weight or obese groups based upon body mass index (BMI) centile and followed up until the completion of treatment. Primary outcome was treatment duration, and secondary outcomes included treatment outcome (occlusal change measured using peer assessment rating [PAR]), appointment characteristics, and compliance measures. Results A total of 45 patients mean age 14.8 (1.6) years were included in the final analysis. The normal-weight group included 23 patients with mean BMI 19.4 (2.4) kg/m2 and the obese group 22 patients with mean BMI 30.5 (3.8) kg/m2. There were no significant differences in baseline demographics between groups, except for BMI and pre-treatment PAR. The normal-weight group had a mean pre-treatment PAR of 25.6 (8.3) and the obese 33.3 (11.8) giving the obese group a more severe pre-treatment malocclusion (P = 0.02). There were no significant differences in treatment duration between groups (P = 0.36), but obese patients needed less time per each additional baseline PAR point compared to normal weight (P = 0.02). Obese patients also needed less appointments compared to normal-weight patients (P = 0.02). There were no significant differences between groups for appointment characteristics or compliance. Finally, obese patients were more likely to experience a great PAR reduction than normal-weight patients (relative risk = 2.6; 95% confidence interval = 1.2–4.2; P = 0.02). Conclusions There were no significant differences in treatment duration between obese and normal-weight patients. Obesity does not appear to be a risk factor for negative orthodontic treatment outcome with fixed appliances.

Summary Background Orthodontic patients wearing fixed appliances are susceptible to traumatic dental injuries during a wide range of sporting activities. This randomized clinical trial investigated wearability and preference of mouthguards during sporting activities in patients undergoing orthodontic treatment with fixed appliances. Methods A prospective three-arm crossover randomized clinical trial conducted in the UK. Thirty patients in active orthodontic treatment with fixed appliances undertaking at least 120 minutes of contact sport per 6–8-week observation period were randomly assigned to one of six mouthguard allocation sequences consisting of three mouthguard types: (MG1) custom-made laboratory constructed, (MG2) mouth-formed OPRO® Gold Braces, and (MG3) pre-fabricated Shock Doctor® Single Brace. Patients completed a nine-outcome 100-mm visual analogue scale (VAS) questionnaire relating to mouthguard wearability during sport. Once feedback was completed, subjects were allocated the next mouthguard in the sequence. At study-end, subjects were asked to identify their preferred mouthguard. Results Twenty-four patients (median age = 13; inter-quartile range 12–14.5 years) completed n = 72 follow-up questionnaires with most playing rugby union or field hockey. Considering VAS score as a continuous variable, for comfort, stability, hardness, ability to breathe, ability to not cause nausea, and inclination to chew, MG2 performed better than MG3. For categorization of VAS score into low (less than 80 mm) or high (at least 80 mm) wearability, for comfort, stability, ability to not cause nausea, and inclination to chew, MG1 and MG2 also rated superior to MG3. Patients preferred MG1 overall. Conclusions This randomized clinical trial found that during contact sport patients in fixed appliances reported superior wearability for custom-made and mouth-formed mouthguards in comparison to pre-fabricated. Overall, patients preferred custom-made mouthguards. Clinical trials registration ClinicalTrials.gov: NCT04588831.

Introduction We have investigated orofacial pain in a prospective cohort of obese and normal-weight subjects undergoing fixed-appliance orthodontic treatment. Methods Fifty-five subjects (27 males, 28 females) mean age 15.1 (1.6) years and mean body mass index 30.2 (3.5) in obese and 19.4 (2.2) kg/m2 in normal-weight groups were followed for 1 week after appliance placement. Primary outcome was maximum-pain measured using a 100-mm visual analogue scale. Secondary outcomes included mean pain and oral analgesic consumption. Results Mean maximum pain for the total sample was 73.7 (standard deviation 14.8; 95% confidence interval 69.8-77.7) mm with no significant differences among groups (P = 0.247). However, mean maximum pain was higher at all time-points for the obese group and significant at 72 hours (P = 0.034). Total analgesia consumed by the obese group was also significantly higher than normal weight (P = 0.041). Multivariable regression found the only significant predictor for mean pain was time. After adjusting for confounding, obesity was associated with higher (+4.47 mm) mean pain at each time-point (P = 0.018). A significant association existed between obesity and total analgesic consumption (univariable-analysis, P = 0.035; multivariable analysis, P = 0.023). After accounting for confounders, obese patients were associated with taking a higher quantity of oral analgesics. Conclusions We found a trend towards increased mean pain and an association with increased analgesic consumption in obese subjects during the first week following fixed-appliance placement.

Summary Background The use of orthodontic aligners to treat a variety of malocclusions has seen considerable increase in the last years, yet evidence about their efficacy and adverse effects relative to conventional fixed orthodontic appliances remains unclear. Objective This systematic review assesses the efficacy of aligners and fixed appliances for comprehensive orthodontic treatment. Search methods Eight databases were searched without limitations in April 2019. Selection criteria Randomized or matched non-randomized studies. Data collection and analysis Study selection, data extraction, and risk of bias assessment was done independently in triplicate. Random-effects meta-analyses of mean differences (MDs) or relative risks (RRs) with their 95% confidence intervals (CIs) were conducted, followed by sensitivity analyses, and the GRADE analysis of the evidence quality. Results A total of 11 studies (4 randomized/7 non-randomized) were included comparing aligners with braces (887 patients; mean age 28.0 years; 33% male). Moderate quality evidence indicated that treatment with orthodontic aligners is associated with worse occlusal outcome with the American Board of Orthodontics Objective Grading System (3 studies; MD = 9.9; 95% CI = 3.6–16.2) and more patients with unacceptable results (3 studies; RR = 1.6; 95% CI = 1.2–2.0). No significant differences were seen for treatment duration. The main limitations of existing evidence pertained to risk of bias, inconsistency, and imprecision of included studies. Conclusions Orthodontic treatment with aligners is associated with worse treatment outcome compared to fixed appliances in adult patients. Current evidence does not support the clinical use of aligners as a treatment modality that is equally effective to the gold standard of braces. Registration PROSPERO (CRD42019131589).

Summary Objective This cross-sectional study aimed to explore the level of knowledge and expectations people deciding on a future orthodontic treatment have about post-orthodontic retention and to investigate the influence of sociocultural characteristics. Material and methods A total of 227 consecutive people involved as legal decision maker (as patient, parent, or legal guardian) for a prospective orthodontic treatment (mean age 37.1 years; 37.3 per cent male) received before their first appointment a questionnaire to assess their knowledge and expectations about post-orthodontic retention. Data were analysed descriptively, whereas predictors were identified with logistic regressions at P value of less than or equal to 0.05. Results Among the 220 responders, 46.3 per cent (n = 99) knew that retention appliances are used after orthodontic treatment and 52.8 per cent (n = 113) believed perfect results can guarantee stability, whereas at the same time, 77.8 per cent (n = 168) knew that teeth can move on their own without any orthodontic appliances. The majority considered stability of the orthodontic result important or extremely important (94.5 per cent; n = 206), preferred bonded over removable retainers (67.2 per cent; n = 133), believed the orthodontist to be primarily responsible for a stable result (73.2 per cent; n = 158), and found it appropriate to charge for recall visits (72.9 per cent; n = 153). Participants’ gender, age, education, nationality, and past orthodontic experiences within the close family significantly influenced answers. Limitations The setting of a single-centred survey conducted in one university moderates the generalizability of the portrayed results. Conclusions Although stability of orthodontic treatment results is very important to people deciding about a prospective orthodontic treatment, knowledge regarding the need for post-orthodontic retention varies and may at times be contradictious. Sociocultural factors seem to influence the level of knowledge and the expectations on post-orthodontic retention.

Background: Orthodontically induced external root resorption (OIRR) is a pathologic consequence of orthodontic tooth movement. However, the limitations of two-dimensional radiography suggest that cone beam computed tomography (CBCT) with its three-dimensional capabilities might be more suitable to assess OIRR. Objective: The aim of this study was to assess in an evidence-based manner data on linear or volumetric OIRR measurements of permanent teeth by means of CBCT, during and/or after the end of orthodontic treatment. Search methods: Unrestricted electronic and hand searches were performed up to January 2017 in 15 databases. Selection criteria methods: Randomized clinical trials, prospective, and retrospective non-randomized studies assessing OIRR during and/or after orthodontic treatment using CBCT in human patients were included. Data collection and analysis: After duplicate study selection, data extraction, and risk-of-bias assessment according to the Cochrane guidelines, random-effects meta-analyses, followed by subgroup, meta-regression, and sensitivity analyses were also performed in order to evaluate factors that affect OIRR. Results: A total of 33 studies (30 datasets) were included in the qualitative analysis while data from 27 of them were included in the quantitative analysis. Direct comparisons from randomized trials found little to no influence of appliance-related factors on OIRR. Explorative analyses including non-randomized studies found a pooled OIRR of 0.79 mm based on all included studies and 0.86 mm when OIRR was assessed at the end of orthodontic treatment. Statistically significant differences in OIRR were found according to tooth type or jaw, inclusion of extractions, treatment duration, and diagnostic accuracy of the CBCT. Conclusions: Based on the results of this study, CBCT seems to be a reliable tool to examine OIRR during or at the end of orthodontic treatment. Although the average OIRR measured with CBCT seems to lack clinical relevance, there are certain factors that may affect OIRR following orthodontic treatment. Nevertheless, due to data heterogeneity and low quality of the included studies, the corresponding results should be interpreted with some caution.

Background Insertion of orthodontic fixed appliances has been known to induce a mostly transient qualitative and quantitative alteration of the intraoral microbiota. However, the extent to which treatment with fixed appliances might have a lasting adverse effect on the periodontal attachment of the teeth has not yet been investigated in an evidence-based manner. Objectives Aim of this systematic review was to assess the effect of comprehensive treatment with fixed orthodontic appliances on clinical attachment levels of adolescent and adult periodontally healthy patients. Search methods Seven databases were searched from inception to February 2017. Selection criteria Prospective non-randomized longitudinal clinical studies. Data collection and analysis After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, Paule-Mandel random-effects meta-analyses of the clinical attachment loss and its 95 per cent confidence intervals (CIs) were calculated. Results A total of 9 trials were identified that included 335 treated patients (at least 34 per cent male / 66 per cent female) with an average age of 22.6 years. The average pooled clinical attachment loss was 0.11 mm (9 studies; 335 patients; 95 per cent CI = 0.12 mm gain to 0.34 mm loss; P = 0.338) with high heterogeneity. Furthermore, one study hinted that a small amount of clinical attachment might be gained by intrusion of upper incisors. Additional analyses indicated that the results were robust to addition of untreated patient groups, while patient age and timing of outcome measurement might play an important role. Conclusions According to existing evidence from longitudinal clinical studies orthodontic treatment with fixed appliances has little to no clinically relevant effect on periodontal clinical attachment levels.

Background Permanent canines are amongst the teeth most affected by impaction and ectopic eruption. Although impacted canines are often subjected to surgical exposure and alignment with either the open or the closed technique for many decades, their treatment effects have not yet been systematically asssessed. Objectives The aim of this systematic review was to critically assess whether significant differences exist in the outcomes of the open or closed surgical exposure of impacted canines. Search methods An unrestricted electronic search of nine databases from inception to December 2016 was performed. Selection criteria methods Included were randomized or prospective non-randomized studies comparing open versus closed exposure of impacted canines in human patients. Data collection and analysis After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, random-effects meta-analyses of mean differences (MDs) and odds ratios (ORs), including their 95 per cent confidence intervals (CIs) were performed, followed by subgroup and sensitivity analyses. Results A total of eight unique studies and a total of 433 (30.1% male/59.9% female) patients were included, with an average age of 15.2 years and a total of 453 impacted canines (48.6% and 51.4% in the open and closed exposure, respectively). Open exposure of impacted canines was associated with reduced duration of canine alignment (two studies; MD = -2.14 months; 95% CI = -4.23 to -0.05 months; P < 0.05; moderate heterogeneity and moderate quality) and lower odds of tooth ankylosis (one study; OR = 0.15; 95% CI = 0.03-0.83; P < 0.05; low quality) compared to closed exposure; both findings being independent of canine localization. However, initial alignment of palatally impacted canines took overall significantly longer than labially impacted canines (8.87 versus 4.17 months). Conclusions Based on existing evidence, open surgical exposure seems to be superior in treatment duration and ankylosis risk over the closed technique. Due to the limited number of small included trials, further research is needed for robust clinical recommendations. Registration PROSPERO (CRD42016051916).

INTRODUCTION Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application. METHODS A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled. The tooth varied in the crown-root angle (CRA) between 156°, 170°, and 184°. An 0.018-inch slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 × 0.025-inch β-titanium wire was modelled. Bracket torque prescription varied between 0°, 12°, and 22°, with bracket placement at the centre of the middle, gingival or incisal third of the crown. A total of 27 models were generated and a buccal root torque of 30° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analysed statistically. RESULTS The palatal crown displacement was significantly affected by bracket positioning (up to 94 per cent), while the buccal apex displacement was significantly affected by bracket prescription (up to 42 per cent) and bracket positioning (up to 23 per cent). Strains in the PDL were affected mainly by CRA (up to 54 per cent), followed by bracket positioning (up to 45 per cent). Finally, bracket prescription considerably affected the stresses in the bracket (up to 144 per cent). LIMITATIONS These in silico results need to be validated in vivo before they can be clinically extrapolated. CONCLUSION Tooth anatomy and the characteristics of the orthodontic appliance should be considered during torque application.

Background: Although the headgear appliance has been used extensively to correct anteroposterior discrepancies, its treatment effects have not yet been adequately assessed in an evidence-based manner. Objective: Aim of this systematic review was to assess the therapeutic and adverse effects of early headgear treatment from controlled clinical trials on human patients in an evidence-based manner. Search methods: An unrestricted electronic search of six databases from inception to December 2015. Selection criteria: Randomized and prospective non-randomized controlled trials assessing the effects of headgear treatment on human patients. Data collection and analysis: After duplicate study selection, data extraction, and risk of bias assessment according to the Cochrane guidelines, random-effects meta-analyses of mean differences (MDs) and relative risks (RRs), including their 95% confidence intervals (CIs) were performed, followed by subgroup and sensitivity analyses. Results: A total of 18 unique studies with a total of 930 (56% male/44% female) patients were included. Headgear treatment was associated with a posterior translation of the anterior maxilla border in the short term, as seen by the mean annualized change in the SNA angle (MD = −1.63°/year; 95% CI = −2.20 to −1.06°/year; high quality evidence) compared to untreated patients. This effect was independent of the rotation of the palatal plane and the inclination of the upper incisors, while a proportional relationship with the initial discrepancy in SNA was seen. The clinical significance of this improvement diminished in the long term, although only limited evidence existed. Additionally, early headgear treatment might decrease the risk of dental trauma during the following years (RR = 0.34; 95% CI = 0.14 to 0.80; moderate quality evidence). Low quality evidence on the effect of headgear on the rotation of the palatal plane, the nasolabial angle, the occlusal outcome, and signs of temporomandibular disorders precluded robust assessments, due to risk of bias, inconsistency, imprecision, and small-study effects. Conclusions: Based on existing trials, headgear is a viable treatment option to modify sagittal growth of the maxilla in the short term in Class II patients with maxillary prognathism. Registration: PROSPERO (CRD42015029837). Funding: None.

INTRODUCTION Biomechanical analysis of orthodontic tooth movement is complex, as many different tissues and appliance components are involved. The aim of this finite element study was to assess the relative effect of material alteration of the various components of the orthodontic appliance on the biomechanical behaviour of tooth movement. METHODS A three-dimensional finite element solid model was constructed. The model consisted of a canine, a first, and a second premolar, including the surrounding tooth-supporting structures and fixed appliances. The materials of the orthodontic appliances were alternated between: (1) composite resin or resin-modified glass ionomer cement for the adhesive, (2) steel, titanium, ceramic, or plastic for the bracket, and (3) β-titanium or steel for the wire. After vertical activation of the first premolar by 0.5mm in occlusal direction, stress and strain calculations were performed at the periodontal ligament and the orthodontic appliance. RESULTS The finite element analysis indicated that strains developed at the periodontal ligament were mainly influenced by the orthodontic wire (up to +63 per cent), followed by the bracket (up to +44 per cent) and the adhesive (up to +4 per cent). As far as developed stresses at the orthodontic appliance are concerned, wire material had the greatest influence (up to +155 per cent), followed by bracket material (up to +148 per cent) and adhesive material (up to +8 per cent). LIMITATIONS The results of this in silico study need to be validated by in vivo studies before they can be extrapolated to clinical practice. CONCLUSION According to the results of this finite element study, all components of the orthodontic fixed appliance, including wire, bracket, and adhesive, seem to influence, to some extent, the biomechanics of tooth movement.

SUMMARY BACKGROUND: Fixed-appliance treatment is a major part of orthodontic treatment, but clinical evidence remains scarce. OBJECTIvES: Objective of this systematic review was to investigate how the therapeutic effects and sideeffects of brackets used during the fixed-appliance orthodontic treatment are affected by their characteristics. SEARCh METhODS AND SElECTION CRITERIA: We searched MEDlINE and 18 other databases through April 2012 without restrictions for randomized controlled trials and quasi-randomized controlled trials investigating any bracket characteristic. DATA COllECTION AND ANAlYSIS: After duplicate selection and extraction procedures, risk of bias was assessed also in duplicate according to Cochrane guidelines and quality of evidence according to the Grades of Recommendation. Assessment, Development and Evaluation approach. Random-effects meta-analyses, subgroup analyses, and sensitivity analyses were performed with the corresponding 95 per cent confidence intervals (CI) and 95 per cent prediction intervals (PI). RESUlTS: We included 25 trials on 1321 patients, with most comparing self-ligated (S l) and conventional brackets. Based on the meta-analyses, the duration of orthodontic treatment was on average 2.01 months longer among patients with S l brackets (95 per cent CI: 0.45 to 3.57). The 95 per cent PIs for a future trial indicated that the difference could be considerable (−1.46 to 5.47 months). Treatment characteristics, outcomes, and side-effects were clinically similar between S l and conventional brackets. For most bracket characteristics, evidence is insufficient. Some meta-analyses included trials with high risk of bias, but sensitivity analyses indicated robustness. CONClUSIONS: Based on existing evidence, no clinical recommendation can be made regarding the bracket material or different ligation modules. For S l brackets, no conclusive benefits could be proven, while their use was associated with longer treatment durations.