Transversal changes, space closure, and efficiency of conventional and self-ligating appliances

Posttreatment stability following therapy using passive self-ligating brackets: extraction vs. nonextraction

PURPOSE

This study aimed to evaluate the effects of lower premolar extraction on posttreatment stability one year following fixed orthodontic treatment with passive self-ligating brackets (Damon system, Ormco, Orange, CA, USA).

METHODS

All patients were treated with fixed orthodontic appliances using passive self-ligating brackets (Damon). For retention, removable Hawley retainers were used. Two groups of patients were included in the study. Each group consisted of 23 patients: group Ex consisted of 10 male and 13 female patients (13.4 ± 1.6 years old) with extraction of lower first premolars and group NonEx consisted of 11 male and 12 female patients (13.4 ± 3.9 years old) without dental extractions. The patients' dental models and photographs were assessed at T0 (pretreatment), T1 (the end of active orthodontic treatment: 3.3 ± 1.0 years in the Ex and 2.3 ± 0.8 years in the NonEx group) and at T2 (1 year posttreatment). All lower casts were scanned and the following dental parameters were recorded and compared between the two groups: intercanine width (ICW), anterior arch width (AAW), intermolar width (IMW), Little's irregularity index (LII) and gingival recessions.

RESULTS

An increase in ICW (group Ex: 1.20 ± 2.51 mm and group NonEx: 0.84 ± 1.48 mm) by the end of active treatment (T1; P < 0.05), as well as a relapse regarding the ICW (group Ex: -0.1 ± 0.47 mm and group NonEx: -67% ± 0.38 mm) one year post-treatment (T2) were recorded in the samples. Relapse in the non-extraction group was statistically and clinically significant, whereas ICW values remained relatively stable in the extraction group during the posttreatment period (T1-T2). The irregularity index decreased during treatment (group Ex: -8.79 ± 6.36 mm and group NonEx: -5.24 ± 2.99 mm) and relapsed in both groups (group Ex: 0.57 ± 90 mm and group NonEx: 0.27 ± 0.53). The rate of relapse in LII was correlated to the relapse rate of ICW. A reduction of IMW was recorded in the Ex group (-1.89 ± 1.82 mm) during active treatment (P < 0.05), which remained stable 1 year posttreatment. AAW increased in both groups (group Ex: 2.77 ± 1.77 mm and group NonEx: 1.77 ± 2.04 mm) throughout active treatment and remained stable at T2.

CONCLUSION

Intergroup comparison revealed that ICW remained stable 1 year posttreatment in the Ex group, whereas high relapse of ICW was recorded in the NonEx group. Furthermore, risk of a relapse of LII appears to be higher in cases with a relapse of the ICW.

Simplifying two-vector mechanics calculations for challenging tooth movements

The purpose of this article was to describe a simple graphical driven method for determining the necessary two-vector mechanics (TVM) as an alternative solution to the ideal or single force. In orthodontics, some tooth movements are difficult to achieve, mainly because of the impossibility of getting the point of application for the necessary force system. Given two points in biomechanically accessible areas, adding together two vectors applied to those points will result in an equivalent force system. The method was developed based on previous research, 3,880 hypothetical cases were analyzed to determine the trends between the resulting forces and their relative locations. A graphical driven TVM method (GTVM) for establishing the necessary TVM is presented in a manner that combine different procedures from the traditional method that simplify the analysis and may allow the user to perform more complex orthodontic cases making easier to compare systems of force equivalents.

Comparison of the sliding resistance between three models of self-ligating ceramic brackets: An in vitro and micro-morphological study

OBJECTIVE

The main objective of our study was to compare a new model of self-ligating ceramic bracket (Clarity™ Ultra by 3M™), to its competitors by evaluating their resistance to sliding during an in vitro simulation of canine retraction.

MATERIAL AND METHODS

The sample consisted of 120 brackets (30 brackets in each group: Victory Twin Series LP™, Clarity Ultra™ by 3M™, Damon Clear 2™ by Ormco™ and Empower™ 2 Clear by American Orthodontics™). Canine retraction was simulated using a universal testing machine connected to a software that measured the average sliding resistance (ASR) for each group. Five brackets from each group were randomly selected and observed under a digital optical microscope at ×50 magnification. ANOVA test and Tukey's analysis were carried to detect statistically significant differences between the groups' sliding resistance values, at the risk of α=0.05.

RESULTS

Measured ASR values of control group (metallic Victory Twin) were the highest ones (70.55g), followed by 3M™ (33.22g) then Damon™ (6.72g) and AO™ (5.49g) (P-value<0.0001). Through microscopic observations, we found that the 3M™ bracket has the lowest percentage of slot chamfering (8%) compared to the other brackets (12%). The 3M™ bracket also has the widest slot followed by AO, and then Damon™. All three bracket types have oversized slots compared to the manufacturer's description, the least oversized being the 3M™ bracket, followed by AO™ and then Damon™. 3M™ and Damon™ brackets have covers that concealed the entire wire in the vertical dimension whereas the AO™ bracket has a curvilinear cover that only shields the gingival part of its slot. Wire-play is zero for the 3M™ group, and 0.1mm for the other two groups.

CONCLUSION

Clarity Ultra™ ceramic bracket produced by 3M™ does not perform well against friction forces compared to its competitors and that is due to its micro-morphological characteristics.

Duration of canine retraction with fixed appliances: A systematic review and meta-analysis

INTRODUCTION

Space closure is a challenging and time-consuming phase of orthodontic treatment with fixed appliances. This systematic review evaluated canine retraction duration using fixed appliances after maxillary first premolar extraction.

METHODS

Unrestricted systematic literature searches were conducted in 8 databases for randomized clinical trials, assessing the duration and rate of maxillary canine retraction using fixed appliances with or without treatment adjuncts published up to July 2021. Study selection, data extraction, and risk of bias evaluation were conducted independently and in duplicate. Random-effects meta-analyses of average rates or mean differences (MD) and 95% confidence intervals (CI) were conducted at α = 5%, followed by sensitivity and Grading of Recommendations Assessment, Development, and Evaluation analysis.

RESULTS

Fifty randomized clinical trials (6 parallel and 44 split-mouth designs) covering 811 participants (mean age 19.9 years; 34% male) were included. The estimated average pooled duration to achieve complete canine retraction was 4.98 months (2 trials; 95% CI, -2.9 to 12.88 months). Pooled average canine retraction was 0.97 mm at months 0-1 (23 trials; 95% CI, 0.79-1.16), 1.83 mm at months 0-2 (20 trials; 95% CI, 1.52-2.14), 2.44 mm at months 0-3 (23 trials; 95% CI, 2.10-2.79), 3.49 mm at months 0-4 (6 trials; 95% CI, 1.81-5.17) and 4.25 mm at months 0-5 (2 trials; 95% CI, 0.36-8.14). Surgically-assisted orthodontics was associated with greater canine retraction at all time points: months 0-1 (10 trials; MD, 0.52 mm; P = 0.004), months 0-2 (8 trials; MD, 0.53 mm; P = 0.04), months 0-3 (8 trials; MD, 0.67 mm; P = 0.01), and months 0-4 (3 trials; MD, 1.13 mm; P = 0.01), whereas subgroup analyses indicated significant effects of anchorage reinforcement method and bracket slot size on canine retraction.

CONCLUSIONS

The average time to achieve complete retraction of the maxillary canine using fixed appliances was around 5.0 months. Most studies used split-mouth randomization to investigate canine retraction for around 1-3 months, with substantial heterogeneity across studies. At 3 months of treatment, high-quality evidence supported greater canine retraction with surgically-assisted orthodontics.

The Efficacy of Accelerating Orthodontic Tooth Movement by Combining Self-Ligating Brackets With One or More Acceleration Methods: A Systematic Review

This review aimed to evaluate the effectiveness of using one or more acceleration methods with self-ligating brackets to accelerate orthodontic tooth movement in adults and the associated effects of these interventions. An electronic search of the following databases (PubMed, Scopus, Google Scholar, EMBASE) was performed (From January 1990 to November 2021). ClinicalTrials.gov and the International Clinical Trials Registry Platform were also electronically searched to find any unpublished studies and ongoing trials. The selected randomized controlled trials (RCTs) involved adult patients treated using self-ligating brackets combined with one or more acceleration methods compared with self-ligating brackets or conditional brackets alone. The risk of bias was assessed using Cochrane's risk of bias tool. A total of seven RCTs and one controlled clinical trial (CCT) were included in this review. Combining self-ligating brackets with flapless corticotomy, low-level laser therapy (LLLT), and infrared light accelerated orthodontic movement by 43% and 50% for surgical methods, 20-50% for LLLT, and 22% for infrared light. Regarding side effects on periodontal tissues, neither flapless corticotomy nor low-frequency vibrational forces caused any damage. Combining self-ligating brackets and flapless corticotomy, low-level laser, or infrared light effectively accelerated orthodontic movement by 20% to 50 %. In contrast, the combination of self-ligating brackets with vibrational forces did not affect speeding tooth movement. The acceleration methods did not have any side effects on the periodontal tissues, but the available evidence was insufficient. There is a need for further primary research regarding the effectiveness of combining self-ligating brackets with acceleration methods and the possible untoward side effects.

Operating time for wire ligation with self-ligating and conventional brackets: A standardized in vitro study

OBJECTIVE

Operating time is one of the main advantages attributed from the literature to the use of self-ligating brackets (SLB). The aim of this study is to investigate the time needed for a complete archwire change procedure with conventional brackets (CB) and SLBs in a standardized in vitro research setting, comparing operators with different expertise.

MATERIALS AND METHODS

Thirty-three participants were divided into three equal groups: undergraduate students, postgraduate students, and orthodontists. Three sets of typodonts bonded with three types of brackets, including passive SLBs, active SLBs, and CBs using both steel and elastic ligatures were investigated. Operators had to insert, ligate, deligate, and remove wires in sets of typodonts representing an actual dentition before and after orthodontic treatment, mounted in phantoms. Archwire change procedure times were compared between the different bracket/ligation systems, between the before- and after-treatment typodonts, and between operators.

RESULTS

There were significant differences between SLBs and CBs, the greatest difference being 11 min 16 s between passive SLBs and CBs ligated with metallic ligatures at T0, for the total archwire change procedure by the operators overall. For all the operators, there was a statistically significant difference in total archwire change procedure time between the systems. The undergraduate students were the slowest when using CBs, but they showed no significant difference compared to the other users when using SLBs.

CONCLUSION

SLBs can offer a significant operating time reduction compared to CBs, and time saving is not dependent on the operator's experience and training.

Stability of transverse dental arch dimension with passive self-ligating brackets: a 6-year follow-up study

Objective

The stability of the transverse expansion in passive self-ligating bracket treatments is a debated topic in orthodontics. However, to date, only 3 reports are available in the literature, with the maximum follow-up of 3 years after the end of therapy. The present study aims to evaluate the stability of orthodontic treatment with self-ligating brackets in a 6-year follow-up period of time.

Materials and methods

A sample of 56 non-extractive cases (of whom 33 females, mean age 16.9, SD = 9.0 years) consecutively treated with Damon® system was retrospectively selected. All patients received fixed retainers from canine to canine in both arches at the end of treatment, and no removable retainers were provided. The mean values of the transverse intercusp, transverse centroid and transverse lingual distances were evaluated for all teeth from canines to second molars in both arches. Each measure was calculated at four timepoints: before treatment (T0), at the end of treatment (T1), one year after treatment (T2) and six years after treatment (T3). Transverse diameters were measured for all teeth, starting from the canines to the second molars, for a total of 1680 observations, and subsequently compared in order to evaluate intra-treatment and post-treatment modifications.

Results

There were increases in all transverse dental measurements during active treatment. A statistically significant (p < .05) reduction of the transverse diameter was found, for upper and lower premolars, from T1 to T3.

Conclusion

The 6-year follow-up analysis detected that the initial transverse expansion showed a statistically significant relapse in premolars. No relapse was detected at the level of canines, due to the presence of fixed retainers, and minimal at first molars.

An Umbrella Review of Systematic Reviews With or Without Meta-Analysis Assessing Treatment Outcomes and Efficiency of Self-Ligating Brackets

Introduction

Self-ligating bracket systems are popular and seem to demonstrate lesser friction, allowing tooth movement without exerting unwanted forces on surrounding structures. This umbrella review aimed to compare self-ligating and conventional bracket systems for treatment efficiency.

Methods

An electronic search in 8 databases was performed for literature published between January 1, 1990, and October 1, 2021, with manual hand-searching of references of retrieved articles. Quality assessment was performed using the risk of bias in a systematic tool by 2 independent reviewers. Data were extracted using a prepiloted form (Joanna Briggs Institute) for evidence synthesis. Corrected covered area was calculated to quantify study overlaps across systematic reviews with or without meta-analysis.

Results

605 articles were retrieved, of which 16 were selected. Most included studies had a low risk of bias, except for 6 that showed an unclear risk of bias. Data analysis revealed a reduction in lower incisor proclination, bacterial accumulation, and oral malodor using self-ligating appliances.

Conclusions

Self-ligating systems reduce mandibular incisor proclination, bacterial accumulation, external apical root resorption, chairside time, and oral malodor. No other differences could be demonstrated in comparison with conventional appliance systems.

Is there any difference between conventional, passive and active self-ligating brackets? A systematic review and network meta-analysis

AIM

To test the null hypothesis that there was no difference in treatment efficiency between therapies undertaken with conventional (CBs), passive self-ligating (PSLBs) or active self-ligating (ASLBs) brackets.

MATERIALS AND METHODS

An electronic search was performed in 3 data bases (Pubmed, Web of Science, Cochrane Library) from their origin up to January 2019. Additional references were hand searched. Search was strictly restricted to randomized controlled trials (RCTs) and split-mouth design studies (SMDs). RCTs and SMDs were initially processed separately and subsequently combined in a network meta-analysis. The following variables were evaluated: treatment duration, number of visits, occlusal outcomes, alignment rate, transverse arch dimensional changes, incisor position modification, rate of space closure, anchorage loss, bond failure, root resorption, perception of discomfort during the initial phase of alignment, time to ligate in or to untie an archwire, periodontal variables, quality of life.

RESULTS

On 229 papers, 30 RCTs and 9 SMDs were finally included in this study. Out of 85 comparisons, 16 only revealed statistically significant differences. It was quicker to untie and ligate an 0.014 NiTi arch from/in 6 ASLBs anterior ceramic brackets compared to 6 ceramic CBs. It was also more painful to insert and remove an 0.019×0.025 SS wire in/from PSLB's brackets compared to CB's attachments. Compared to conventional brackets, there was less maxillary incisor proclination with PSLBs in non-extraction cases. Moreover, there was less bleeding on probing 4-5 weeks after bonding with PSLBs compared to CBs brackets. The only significant difference between ASLBs and PSLBs was that alignment was 10 days faster with active self-ligating braces compared with passive self-ligating braces even if treatment duration between ASLBs and PSLBs was not significantly different. The network meta-analysis revealed that IMPA was greater in extractions cases with CBs compared with both ASLBs (+2,5°) and PSLBs (+1,6°).

CONCLUSIONS

The vast majority of the studied variables did not show any significant differences between the three types of brackets. The most significant findings were that it was quicker to insert and remove archwires from ASLBs compared to CBs, and it was more painful to insert and remove an 0.019×0.025" stainless steel wire in/from PSLBs compared to CBs. The major difference between ASLBs and PSLBs was that alignment was 10 days faster with active self-ligating braces compared with passive self-ligating braces even if treatment duration between ASLBs and PSLBs was not significantly different. Most of the claims put forward by the suppliers were not substantiated by our network meta-analysis.

Predictors of orthodontic treatment conclusion: A historical cohort study

INTRODUCTION

The study investigated which patient and orthodontic treatment factors act as predictors for the conclusion of the ongoing treatment in a dental clinic of a specialization program in Orthodontics.

METHODS

Data were collected from the records of patients treated from 1997 to 2015. Potential predictors for treatment conclusion were investigated: patient-related factors (PRFs) and treatment-related factors (TRFs). PRFs were sex, age, face balance, Angle malocclusion classification, open bite, denture, facial pattern, facial profile, buccal corridor, crossbite, maxillary deficiency, and sagittal mandibular behavior; and TRFs were therapeutic approaches, treatment modality, extractions, and Bolton discrepancy. The initial and final treatment dates were collected. Descriptive data analysis, univariate, and multivariate logistic regression were performed (5% significance).

RESULTS

Of the 903 records, 561 patients were included in the study. It was demonstrated that starting the treatment at a young age (PRF) and the presence of crossbite (TRF) are predictive factors for the treatment conclusion. A vertical facial pattern (dolichofacial or brachyfacial) and a greater number of extractions for orthodontic reasons may contribute positively to the conclusion of the treatment. The frequency of treatment inconclusion was higher during the first 2 years of treatment (more than 50% of the patients that initiated the treatment).

CONCLUSIONS

Young age at the beginning of treatment and the presence of crossbite malocclusion can increase the chance of treatment conclusion.

Inter-premolar width changes related to the orthodontic traction of maxillary impacted canines in adolescents and young adults: A retrospective CBCT study

OBJECTIVE

Maxillary canine impaction is directly associated with a narrow maxillary arch, mainly in the inter-premolar widths. This study compared the transverse changes at the level of maxillary premolars after traction of maxillary impacted canines (MICs) in adolescents and young adults through three main goals: to compare unilateral versus bilateral cases, to compare buccally versus palatally MIC cases, and to compare the affected versus non-affected side exclusively in the unilateral group.

METHODS

This before and after CBCT study involved 45 MIC orthodontically tractioned until the occlusal plane with a standardized protocol. The sample was classified regarding the impaction type (unilateral versus bilateral), impaction location (palatal versus buccal) and the affected versus unaffected sides in the unilateral cases. MIC characteristics as impaction sector, height, and complexity of the traction, as well as α and β angles, canine root length and area were measured. Moreover, cephalometric characteristics were also evaluated. Mann-Whitney U or Wilcoxon signed-rank tests and multiple regressions were applied (α=0.05).

RESULTS

Maxillary inter-premolar widths (first or second) expanded approximately 3mm after traction of unilateral or bilateral MIC (P>0.05). Changes in hemi-arch widths between palatal (1.67mm) versus buccal (1.90mm) MIC were similar (P>0.05). In unilateral impaction, the transversal changes on the affected side were 2mm versus almost 1mm observed in the unaffected side (P<0.05). Finally, the multiple linear regressions were identified to the ANB angle, the impaction sectors and the distance from middle raphe to the cusp tip of MIC as influential variables.

CONCLUSION

The maxillary inter-premolar widths increase after traction of MIC without differences between type or location of impaction. In addition, the transverse change in the affected side in unilateral MIC is greater than the unaffected side resolving the earlier transverse asymmetry.

Comparison of changes in the dental transverse and sagittal planes between patients treated with self-ligating and with conventional brackets

INTRODUCTION

Several advantages have been established regarding the efficiency of self-ligating brackets (SL). In spite of some controversy surrounding this question in the literature, clinical results confirm that "arch development" requires fewer extractions.

OBJECTIVE

The objective of this study was to compare changes in the transverse and sagittal planes in patients treated with conventional ligating brackets (CL)as well as in patients treated with SL brackets and oversized arches.

METHODS

A sample was selected from a pool of 300 consecutive cases treated by a single clinician: 51 patients with SL brackets and oversized wires, and 55 with CL brackets. These two groups were compared with a control group of 20 patients. All plaster models were scanned and dental landmarks were measured to identify changes from commencement (T0) to conclusion (T1) of treatment. Lateral cephalograms were analyzed for changes in the lower incisor (IMPA) and the first lower molar distal angulation (MAng). Intraoperator reliability was tested with linear regression analysis. To assure all groups were comparable at T0, an ANOVA test with a 95%confidence interval (CI) was performed for all values. To assess changes from T0 to T1 in all groups, a Student's t-test with 95% CI was used. Finally, results from the three groups were compared using an ANOVA-test (95% CI) and a post-hoc test.

RESULTS

Increases in all the transverse variables were recorded in the two groups treated (SL and CL), except for the lower intercanine distance in the SL group. IMPA difference from T0 to T1 was higher in the CL group, and molar distal angulation (MAng) took place in the SL group.

CONCLUSIONS

Self-ligating brackets with oversized arches and conventional ligating brackets showed increases in all variables in the transverse plane, except for the SL group at the mandibular intercanine distance. In comparison with the CL group, fewer different IMPA values were observed in the SL group, in which distal molar angulation occurred.

"In Vitro" Study About Variables that Influence in Arch Friction with Conventional and Self-Ligating Brackets

Many advantages have been described surrounding self-ligating (SL) brackets compared to metallic conventional ligating (CL) brackets, such as: Less total treatment time, alignment efficiency, patient comfort, plaque retention, and low friction. The objective of this in vitro simulation was to know the variables that affect arch displacement in CL and SL brackets-active (ASL) and passive (PSL)-and analyze if static friction values are affected by bracket design, arch wire section, kind of ligature, and use of a friction reducer agent (FRA) in a wet state. Larger values of static friction were found in CL with metallic ligature (ML) (8.01 ± 1.08 N/mm) and elastic ligature (EL) (6.96 ± 0.48 N/mm). Lower values were found in PSL brackets combined with FRA (0.58 ± 0.21 N/mm). The study was carried out using different stereographical models of a maxillary upper right quadrant with canine, first and second premolar, and first molar bonded brackets. A section of 25 mm of 0.019 × 0.025" stainless steel arch with a rectangular section (SS) and hybrid section (HY) was inserted into the different bracket models. Static friction values were collected using a universal test machine in wet conditions and testing the effect of a friction reducer agent (FRA). To assure the reliability of the study, different wire combinations were repeated after two weeks by the same operator and a linear analysis of regression was done. Each bracket model analysis-with the different wires, use of the FRA, and comparison among brackets in similar conditions-was done using an ANOVA test with a confidence interval of 95% and comparative Post-Hoc tests (LSD). In this in vitro simulation we found higher static friction values in CL compared to ASL and PSL. In PSL, lower values were achieved. CL brackets using ML showed the highest static friction values with a great variability. In this setting, the use of HY wires did not reduce static friction values in ASL and PSL, while in CL brackets with EL friction the values were reduced significantly. An FRA combined with ASL reduced significantly static friction values but not with PSL. In the case of CL, the FRA effect was higher with SS and better than with HY wires. ML values were similar to ASL static friction. The direct extrapolation of the results might be inaccurate, since all these findings should be tested clinically to be validated.