Self-ligating brackets: present and future

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.

Qualitative and Quantitative Evaluation of Different Types of Orthodontic Brackets and Archwires by Optical Microscopy and X-ray Fluorescence Spectroscopy

The wear behaviour and chemical composition of orthodontic components influence the mechanical characteristics of a fixed orthodontic treatment. The purpose of this paper is to evaluate the surface alterations of different types of brackets (aesthetic, metallic, and conventional self-ligating) and archwires (superelastic and thermal) subjected to wear tests through optical microscopy and, subsequently, to identify the chemical elements of accessories by X-ray fluorescence. The cycles (5000 for each bracket and 10,000 for each wire) of the tribological test were carried out in dry conditions inside a machine that allows alternating sliding. The results of the study highlighted different wear behaviours even within the same type of brackets and archwires. The monocrystalline sapphire brackets maintain their aesthetic properties despite traces of wear inside the slots and contain minimal amounts of nickel. Superelastic NiTi archwires have a better overall rating than thermal wires, as they do not show significant surface wear alterations.

An in vitro assessment of the influences of different wire materials and bracket systems when correcting dental crowding

A recently developed orthodontic wire alloy known as GUMMETAL® is claimed to deliver more physiological forces to correct dental mispositioning. However, its mechanical characteristics have not been fully characterized yet. This study aimed to determine and compare the elastic properties of different wire alloys, such as nickel-titanium (NiTi), stainless steel (SS), and GUMMETAL®, and assess their unloading forces when combined with either conventional or self-ligating brackets (CL and SL) when correcting dental crowding. All wires had a 0.016″ cross-section diameter. A three-point bending test was performed to assess the maximum deflection of each wire. Then, a subsequent analysis measured the unloading force for each wire/bracket system in a dental crowding clinical simulation device. The test was carried out in a universal testing machine with a cross-speed displacement of 0.5 mm/min. Data were recorded in different ranges and statistically evaluated using two-way analysis of variance. GUMMETAL® displayed higher unloading mean forces in SL brackets (2228.78 cN) than CL brackets (1967.38 cN) for the 1.6-3.0 deflection interval (p = 0.018). Within this interval, NiTi showed higher forces when used with CL brackets (2683.06 cN) than with SL brackets (1179.66 cN) (p < 0.0001). For the CL bracket systems, SS wires showed higher forces (2125.31 cN) in the 1.0-1.6 deflection interval than the other two wire alloys (NiTi, 1541.52 cN and GUMMETAL®, 852.65 cN) (p < 0.0001). SS wires also displayed lower forces with SL brackets (1844.01 cN) than in CL brackets (2125.31 cN) (p = 0.049). Thus, only GUMMETAL® revealed to be an optimal choice for SL brackets, whereas NiTi for CL brackets.

Rates of tooth movement and bone remodeling activity: Self-ligating versus conventional brackets

Background

Bracket systems have been developed with the purpose of reducing frictional resistance between the archwire and accessories. The aim of this research was to compare rates of tooth movement and regions of cellular bone modeling activity along tooth root surfaces of teeth moved with conventional vs. self-ligating brackets.

Material and Methods

The experiments were conducted in 20 male dogs. Bands were cemented in all intermediate incisors, with conventional brackets (Morelli) on the right side and hybrid self-ligating ones (T3-American Orthodontics) on the left side. A 0.019” x 0.025” stainless steel wire was inserted passively in the slot of these brackets with chain elastics (250 gf) to perform sliding mechanics. Clinical records of the orthodontic mechanics were made before and after 15 days of the tooth movement. The dental segments of the animals were prepared for light microscopy. Statistical analysis of variance and the Tukey correction with a P value at 5% were used.

Results

There were no significant differences in tooth movement rates between the two types of brackets but differences, in the bone modeling activity, suggested that tooth movement with the self-ligating brackets resulted in more tipping and less translational movement than tooth movement with the conventional brackets.

Conclusions

The rates of tooth movement were similar between the two systems. The histological evaluation of cellular bone modeling activity along tooth root surfaces showed more translation movement of teeth with the conventional brackets, and more tipping movement of teeth with self-ligating brackets.

Key words:Edgewise, histological reactions, orthodontic movement, self-ligating, brackets.

Comparison of self-ligating Damon3 and conventional MBT brackets regarding alignment efficiency and pain experience: A randomized clinical trial

Background. Self-ligating brackets might be more efficient than conventional appliance systems during the initial alignment stage of orthodontic treatment due to reduced frictional resistance. This study aimed to compare the alignment efficiency and pain experience of Damon3 self-ligating and MBT pre-adjusted brackets in the initial alignment stage.

Methods. In this randomized clinical trial, 30 patients aged 14‒20 years, who needed non-extraction treatment in both maxillary and mandibular arches, were randomly assigned to two groups; 15 patients were treated with MBT pre-adjusted brackets, and 15 patients received Damon3 self-ligating brackets, both with 0.022-in slots. Alginate impressions were taken at the start of treatment (T0) and four monthly visits (T1, T2, T3, and T4). Little’s irregularity index (LII) was used to assess the tooth displacements. The patients rated their pain experience immediately after the insertion of the archwire, 4 hours, 24 hours, 3 days, 7 days, and at each monthly visit using a visual analog scale (VAS).

Results. The rate of upper dental alignment between T0 and T4 was significantly higher with the Damon3 compared to MBT brackets (P=0.015). Although significantly more changes in the lower LII scores were observed during the first three months with the Damon3 system, the rate of improvement in the irregularity of lower teeth over the 4-month period was not significantly different between the two groups (P=0.50). The patients’ pain experience was not significantly different between the bracket groups (P=0.29).

Conclusion. During the four-month alignment stage, significantly more improvement in the upper dental irregularity was observed with self-ligating compared to conventional brackets. The bracket type had no effect on pain experience during the alignment stage.

Effect of different combinations of bracket, archwire and ligature on resistance to sliding and axial rotational control during the first stage of orthodontic treatment: An in-vitro study

OBJECTIVE

This study was performed to explore the effect of different bracket, archwire, and ligature combinations on resistance to sliding (RS) and rotational control in first-order angulation.

METHODS

Three types of brackets (multi-level low friction [MLF], self-ligating, and conventional brackets) coupled with four nickel-titanium archwires (0.012, 0.014, 0.016, and 0.018-inch diameter) and two stainless steel ligatures (0.20 and 0.25 mm) were tested in different first-order angulations (0°, 2°, 4°, 6°, 8°, 10°, 15°, 20°) by using an Instron universal mechanical machine in the dry state at room temperature. RS value was evaluated and compared by one-way ANOVA.

RESULTS

Under the same angulation, the RS values showed the following order: conventional brackets > MLF brackets > self-ligating brackets. The RS was the highest for conventional brackets and showed a tendency to increase. The RS for MLF brackets coupled with thinner archwires and ligatures showed a similar tendency as the RS for the self-ligating bracket. In contrast, the RS for MLF brackets coupled with thicker archwires and ligatures increased like that for conventional brackets. MLF brackets showed the greatest range of critical contact angles in first-order angulation.

CONCLUSIONS

The RS in first-order angulation is influenced by bracket design, archwire, and ligature dimension. In comparison with self-ligating and conventional brackets, MLF brackets could express low friction and rotational control with their greater range of critical contact angles.

Evaluation of lower anterior dental changes in patients treated with self-ligating brackets

The aim of this study was to evaluate and compare changes in linear distance and inclination of lower incisors and canines and intercanine distance after a 30 months orthodontic treatment with self-ligating appliances. Seven patients were treated orthodontically with a Roth prescription passive self-ligating bracket. To perform the measurements and comparisons, CBCT scans were taken before the start of the orthodontic treatment (T₁) and after a period of 30 months treatment (T₂). The following measurements were performed: (1) the lower incisors and canines inclination in relation to the mandibular plane, (2) intercanine linear distance in millimeters and (3) linear distance in millimeters of the incisal and apical part of lower anterior teeth to a plane (POGM) passing through pogonion point and perpendicular to the mandibular plane. No significant difference were observed between T₁ and T₂ for canine inclination (p = 0.835), incisors inclination (p = 0.149), canine incisal distance to POGM (p = 0.423) and incisors incisal distance to POGM (p = 0.966), however canine apical distance (p = 0.049) and incisors apical distance (p = 0.002) to POGM was lower at T₁ than at T₂. The intercanine distance was significantly lower (p = 0.022) at T₁ when compared to T_2. The use of passive self-ligating brackets in orthodontic treatment to solve 4 mm tooth crowding were able to produce dental arch expansion by bodily tooth movement.

Effectiveness and efficiency in clinical orthodontic practice

Proffitt et al. have described "effectiveness and efficiency" (E&E) as achieving desired results without wasting the orthodontist's and patients' time. In 1972, Archibald Cochrane published a monograph entitled "Effectiveness and Efficiency," which challenged the medical community to use medical protocols that were evidence-based. As a possible starting point for E&E, the orthodontist could consider an "Evidence-based clinical practice" (EBCP) model, which integrates the best research evidence with clinical expertise and patient values. This model considers scientific or evidence-based orthodontics (EBO) together with patient preferences and patient autonomy, clinical or patient circumstances, and clinical experience and judgment. In this paper, therefore, E&E will be discussed from an EBCP perspective which, for our purposes, includes relevant evidence but also our clinical experience and rationale. We will discuss: wire sequence; NiTi Wire types; space closure by sliding; canine retraction versus en masse retraction, 18" slot versus 22" slot, the Bidimensional System; self-ligating brackets (SL); vertical slot; economic aspects.

Comparative study of torque expression among active and passive self-ligating and conventional brackets

OBJECTIVE

The aim of this study was to compare torque expression in active and passive self-ligating and conventional brackets.

METHODS

A total of 300 segments of stainless steel wire 0.019 x 0.025-in and six different brands of brackets (Damon 3MX, Portia, In-Ovation R, Bioquick, Roth SLI and Roth Max) were used. Torque moments were measured at 12°, 24°, 36° and 48°, using a wire torsion device associated with a universal testing machine. The data obtained were compared by analysis of variance followed by Tukey test for multiple comparisons. Regression analysis was performed by the least-squares method to generate the mathematical equation of the optimal curve for each brand of bracket.

RESULTS

Statistically significant differences were observed in the expression of torque among all evaluated bracket brands in all evaluated torsions (p < 0.05). It was found that Bioquick presented the lowest torque expression in all tested torsions; in contrast, Damon 3MX bracket presented the highest torque expression up to 36° torsion.

CONCLUSIONS

The connection system between wire/bracket (active, passive self-ligating or conventional with elastic ligature) seems not to interfere in the final torque expression, the latter being probably dependent on the interaction between the wire and the bracket chosen for orthodontic mechanics.

Comparison of the force levels among labial and lingual self-ligating and conventional brackets in simulated misaligned teeth

Background/objective

The aim of this study was to evaluate force levels exerted by levelling arch wires with labial and lingual conventional and self-ligating brackets.

Materials/methods

The tested orthodontic brackets were of the 0.022-in slot size for labial and 0.018-in for lingual brackets and were as follows: 1. Labial brackets: (i) conventional bracket (GAC-Twin, Dentsply), (ii) passive self-ligating (SL) brackets (Damon-Q®, ORMCO; Ortho classic H4™, Orthoclassic; FLI®SL, Rocky Mountain Orthodontics) and (iii) active SL brackets (GAC In-Ovation®C, DENTSPLY and SPEED™, Strite). 2. Lingual brackets: (i) conventional brackets (Incognito, 3M and Joy™, Adenta); (ii) passive SL bracket (GAC In-Ovation®LM™, Dentsply and (iii) active SL bracket (Evolution SLT, Adenta). Thermalloy-NiTi 0.013-in and 0.014-in arch wires (Rocky Mountain Orthodontics) were used with all brackets. The simulated malocclusion represented a maxillary central incisor displaced 2 mm gingivally (x-axis) and 2 mm labially (z-axis).

Results

Lingual bracket systems showed higher force levels (2.4 ± 0.2 to 3.8 ± 0.2 N) compared to labial bracket systems (from 1.1 ± 0.1 to 2.2 ± 0.4 N). However, the differences between SL and conventional bracket systems were minor and not consistent (labial brackets: 1.2 ± 0.1 N for the GAC Twin and 1.1 ± 0.1 to 1.6 ± 0.1 N for the SL brackets with 0.013-in thermalloy; lingual brackets: 2.5 ± 0.2 to 3.5 ± 0.1 N for the conventional and 2.7 ± 0.3 to 3.4 ± 0.1 N for the SL brackets with 0.013-in Thermalloy).

Limitations

This is an in vitro study with different slot sizes in the labial and lingual bracket systems, results should be interpreted with caution.

Conclusions/implications

Lingual bracket systems showed higher forces compared to labial bracket systems that might be of clinical concern. We recommend highly flexible nickel titanium arch wires lower than 0.013-in for the initial levelling and alignment especially with lingual appliances.

Torque expression in self-ligating orthodontic brackets and conventionally ligated brackets: A systematic review

Background

To evaluate the torque expression of self ligating (SL) orthodontic brackets and conventionally ligated brackets and the torque expression in active and passive SL brackets.

Material and Methods

Our systematic search included MEDLINE, EMBASE, CINAHL, PsychINFO, Scopus, and key journals and review articles; the date of the last search was April 4th 2016. We graded the methodological quality of the studies by means of the Quality Assessment Tool for Quantitative Studies, developed for the Effective Public Health Practice Project (EPHPP).

Results

In total, 87 studies were identified for screening, and 9 studies were eligible. The quality assessment rated one of the study as being of strong quality, 7 (77.78%) of these studies as being of moderate quality. Three out of 7 studies which compared SL and conventionally ligated brackets showed, conventionally ligated brackets with highest torque expression compared to SL brackets. Badawi showed active SL brackets with highest torque expression compared to passive SL brackets. Major and Brauchli showed no significant differences in torque expression of active and passive SL brackets.

Conclusions

Conventionally ligated brackets presented with highest torque expression compared to SL brackets. Minor difference was recorded in a torque expression of active and passive SL brackets.

Key words:Systematic review, self ligation, torque expression, conventional ligation.

Dentoalveolar mandibular changes with self-ligating versus conventional bracket systems: A CBCT and dental cast study

OBJECTIVE:

The aim of the present study was to compare dentoalveolar changes in mandibular arch, regarding transversal measures and buccal bone thickness, in patients undergoing the initial phase of orthodontic treatment with self-ligating or conventional bracket systems.

METHODS:

A sample of 25 patients requiring orthodontic treatment was assessed based on the bracket type. Group 1 comprised 13 patients bonded with 0.022-in self-ligating brackets (SLB). Group 2 included 12 patients bonded with 0.022-in conventional brackets (CLB). Cone-beam computed tomography (CBCT) scans and a 3D program (Dolphin) assessed changes in transversal width of buccal bone (TWBB) and buccal bone thickness (BBT) before (T₁) and 7 months after treatment onset (T₂). Measurements on dental casts were performed using a digital caliper. Differences between and within groups were analyzed by Student's t-test; Pearson correlation coefficient was also calculated.

RESULTS:

Significant mandibular expansion was observed for both groups; however, no significant differences were found between groups. There was significant decrease in mandibular buccal bone thickness and transversal width of buccal bone in both groups. There was no significant correlation between buccal bone thickness and dental arch expansion.

CONCLUSIONS:

There were no significant differences between self-ligating brackets and conventional brackets systems regarding mandibular arch expansion and changes in buccal bone thickness or transversal width of buccal bone.

Alterations in plaque accumulation and gingival inflammation promoted by treatment with self-ligating and conventional orthodontic brackets

OBJECTIVE

The aim of the present study was to evaluate, comparatively, the periodontal response during orthodontic treatment performed with self-ligating and conventional brackets.

METHODS

Sixteen Caucasian individuals of both sexes, aged between 12 and 16 years old and in permanent dentition were selected. Eight individuals were treated with conventional brackets installed on the lower dental arch and self-ligating brackets on the upper arch. Another eight individuals received self-ligating brackets in the lower arch and conventional brackets in the upper arch. The subjects received material and instructions for oral hygiene. Visible plaque index (VPI), gingival bleeding index (GBI) and clinical attachment level (CAL) were evaluated just after installation of orthodontic appliances, and 30, 60 and 180 days later. Mann-Whitney test was used to compare differences between groups (self-ligating and conventional), two-way ANOVA followed by Tukey's test was used to assess CAL at each site of each tooth. Significance level was set at 5%.

RESULTS

No significant changes were found with regard to the assessed parameters (VPI, GBI and CAL) in either one of the systems.

CONCLUSION

No significant changes were found with regard to the periodontal response to orthodontic treatment for the variables assessed and between subjects receiving passive self-ligating and conventional brackets. All individuals had received oral hygiene instructions and had their periodontal conditions monitored.

Frictional force released during sliding mechanics in nonconventional elastomerics and self-ligation: An in vitro comparative study

AIM AND OBJECTIVES

The aim of this study is to evaluate the frictional forces generated by five different orthodontic brackets when used in combination with stainless steel (SS), titanium molybdenum alloy (TMA), and nickel-titanium (NiTi) archwires in dry conditions at physiological temperature.

MATERIALS AND METHODS

Five different types of maxillary upper right side self-ligating brackets (SLBs) (Damon 3MX, Smart Clip and Carriere LX) and conventional SS brackets (Mini 2000, Optimum Series and Victory Series) with a slot size 0.022 inch were coupled with 0.016" NiTi and 0.019 × 0.025" SS/titanium molybdenum alloy (TMA) archwires. Tests were carried out for each group of the bracket-wire combination at physiological temperature and in the dry state. Frictional forces were measured by Instron universal testing machine.

RESULTS

SLB showed lower fictional values in comparison with elastic ligatures. Frictional force increased proportionally to the wire size; TMA and NiTi archwires presented higher frictional resistance than SS archwires.

CONCLUSION

SS brackets tied with conventional ligatures produced high and low friction when ligated with SLBs with passive clip.

The Effect of Using Self-ligating Brackets on Maxillary Canine Retraction: A Split-mouth Design Randomized Controlled Trial

INTRODUCTION

The results of previous studies about the efficacy of using self-ligating brackets (SLBs) in controlling canine movement during retraction are not in harmony. Therefore, the current study aimed to compare the effects of using new passive SLBs on maxillary canine retraction with sliding mechanics vs conventional ligating brackets (CLBs) tied with metal ligatures.

MATERIALS AND METHODS

The sample comprised 15 adult patients (4 males, 11 females; 18-24 years) requiring bilateral extraction of maxillary first premolars. Units of randomization are the left or right maxillary canines within the same patient. The two maxillary canines in each patient were randomly assigned to one of the two groups in a simple split-mouth design. The canines in the SLBs group (n = 15) were bracketed with SLBs (Damon Q™), while the canines in the CLBs group (n = 15) were bracketed with conventional brackets (Mini Master Series). Transpalatal bars were used for anchorage. After leveling and alignment, 0.019 × 0.025" stainless steel working archwires were placed. Canines were retracted using a nickel-titanium close-coil springs with a 150 gm force. The amount and rate of maxillary canine retraction, canine rotation, and loss of anchorage were measured on study models collected at the beginning of canine retraction (T0) and 12 weeks later (T1). Differences were analyzed using paired-samples t-tests.

RESULTS

The effect differences were statistically significant (p < 0.001). Using Damon Q™ SLBs, the amount and rate of canine retraction were greater, while canine rotation and anchorage loss were less.

CONCLUSION

From a clinical perspective, extraction space closure can be accomplished more effectively using SLBs.

CLINICAL SIGNIFICANCE

Self-ligating brackets gave better results compared to the CLBs in terms of rate of movement, amount of canine rotation following extraction, and anchorage loss.

Ceramic brackets and low friction : A possible synergy in patients requiring multiple MRI scanning

AIM

To investigate any advantages of low friction biomechanics in orthodontic patients with fixed appliances without producing metal artifacts during magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Frictional resistance generated by bracket-wire-ligature systems was analyzed via an experimental model that reproduced upper canine misalignment. Each sample was tested 10 consecutive times in a dry state; a total of 160 tests were carried out. We documented the frictional forces generated by a 0.012- and 0.014-inch superelastic nickel-titanium wire (SENT) with ceramic self-ligating brackets (SLB) with metal insert and ceramic monocrystalline brackets with nonconventional elastic ligatures (NCEL) in conjunction with various degrees of canine misalignment (1.5, 3.0, 4.5, and 6.0 mm). Comparisons between the frictional forces released by the two different bracket-wire-ligature systems were made by conducting 3-way analysis of variance (ANOVA) with Tukey HSD pairwise test (P < 0.005).

RESULTS

We observed no clinically relevant difference between the frictional forces released by ceramic SLB and ceramic brackets in conjunction with a 0.012- and 0.014-inch SENT. Statistically significant differences were apparent with a 0.012-inch SENT at 4.5 and 6.0 mm of canine misalignment, where the SLB revealed higher frictional forces.

CONCLUSIONS

Ceramic brackets with NCEL revealed frictional forces similar to those generated in conjunction with ceramic SLB, thereby helping to avoid metal artifacts in case of expected necessary MRI during orthodontic treatment with fixed appliances.

Effect of passive self-ligating bracket placement on the posterior teeth on reduction of frictional force in sliding mechanics

Objective

The purpose of this study was to investigate the static (SFF) and kinetic frictional forces (KFF) in sliding mechanics of hybrid bracket systems that involve placing a conventional bracket (CB) or active self-ligating bracket (ASLB) on the maxillary anterior teeth (MXAT) and a passive SLB (PSLB) on the maxillary posterior teeth (MXPT).

Methods

The samples consisted of two thoroughbred types (group 1, anterior-CB + posterior-CB; group 2, anterior-ASLB + posterior-ASLB) and four hybrid types (group 3, anterior-CB + posterior-PSLB-type 1; group 4, anterior-CB + posterior-PSLB-type 2; group 5, anterior-ASLB + posterior-PSLB-type 1; group 6, anterior-ASLB + posterior-PSLB-type 2) (n = 13 per group). After maxillary dentition alignment and maxillary first premolars removal in the stereolithographically-made typodont system, a 0.019 × 0.025-inch stainless steel wire was drawn through the right quadrant of the maxillary arch at 0.5 mm/min for 5 min. The SFF and KFF were measured with a mechanical testing machine and statistical analyses were performed.

Results

Four different categories of SFF and KFF were observed among all groups (all p < 0.001). Group 1 demonstrated the highest SFF and KFF; groups 4 and 3 were second and third highest, respectively. The fourth category included groups 2, 5, and 6. Placing PSLBs on the MXPT resulted in significant SFF and KFF reductions in cases with CBs on the MXAT, but not in cases with ASLBs on the MXAT.

Conclusions

These data might aid in the development of a hybrid bracket system that enables low-friction sliding of an archwire through the MXPT.

[Brackets and friction in orthodontics: experimental study]

Many authors have been involved in developing brackets in order to improve the quality, stability, speed and efficiency of orthodontic treatment. In order to reduce friction between bracket and archwire, new therapeutic approaches have been devised based on novel technologies. Among these innovative techniques, self-ligating brackets are increasingly popular. SLBs can be classified into several categories according to their mode of action and their materials. We performed an experimental study to compare the friction forces generated during the sliding of orthodontic archwires made from various alloys through conventional and self-ligating brackets. Results show the favorable influence of SLBs, compared to conventional systems using elastomeric or metal ligatures, on the level of friction, particularly when shape-memory Ni-Ti archwires are used.

Actual versus theoretical torsional play in conventional and self-ligating bracket systems

OBJECTIVE

The aim of this study was to assess the amount of torsional play in 32 commercially available self-ligating and conventional 0·018-inch and 0·022-inch bracket systems in relation to 0·017×0·022-inch and 0·019×0·025-inch stainless steel wires, respectively, and compare the results with the theoretical amount of play for the given bracket/wire combinations.

METHODS

Torque moments were measured in a mechanical force testing system by twisting straight pieces of stainless steel wire seated in the bracket slot in increments of 0·5° until a full torsional expression was registered. Five upper central incisor brackets from each of the 32 different bracket systems were selected for the study.

RESULTS

The result from the laboratory testing clearly showed that wire/slot play was larger than anticipated from the nominal values, especially regarding the 0·022-inch brackets and particularly in relation to the passive self-ligating brackets. The play ranged from 19·8 to 36·1° of play for the most imprecise bracket system.

CONCLUSIONS

The result does not favour the use of self-ligating brackets when focussing on torque control. The actual play is larger due to oversized slots and the inability of self-ligation brackets to press the archwire into the bottom of the slot. In conventional brackets, the initial torque moment is generated by the steel ligatures pressing the arch wire against the bottom of the slot. The oversize of the slot is thus less critical in relation to the conventional than in relation to the passive self-ligation bracket.

Effect of self-ligating bracket type and vibration on frictional force and stick-slip phenomenon in diverse tooth displacement conditions: an in vitro mechanical analysis

OBJECTIVE

To evaluate the effects of self-ligating bracket (SLB) type and vibration on frictional force and stick-slip phenomenon (SSP) in diverse tooth displacement conditions when a levelling/alignment wire was drawn.

MATERIALS AND METHODS

A total of 16 groups were tested (n = 10/group): Two types of SLBs [active SLB (ASLB, In-Ovation R) and passive SLB (PSLB, Damon Q)]; vibration (30 Hz and 0.25 N) and non-vibration conditions; and 4 types of displacement [2mm lingual displacement of the maxillary right lateral incisor (LD), 2mm gingival displacement of the maxillary right canine (GD), combination of LD and GD (LGD), and control]. After applying artificial saliva to the typodont system, 0.018 copper nickel-titanium archwire was drawn by Instron with a speed of 0.5mm/min for 5 minutes at 36.5°C. After static/kinetic frictional forces (SFF/KFF), and frequency/amplitude of SSP were measured, statistical analysis was performed.

RESULTS

ASLB exhibited higher SFF, KFF, and SSP amplitude (all P < 0.001) and lower SSF frequency (all P < 0.05) than PSLB in all displacement groups. Vibration decreased SFF, KFF, and SSP amplitude and increased SSP frequency in control and all displacement groups (all P < 0.001). ASLB exhibited lower SSP frequency than PSLB only under non-vibration condition (P < 0.05 in LD and GD, P < 0.01 in LGD). However, regardless of vibration conditions, ASLB demonstrated higher SSP amplitude than PSLB in all displacement groups (all P < 0.001 under non-vibration; all P < 0.01 under vibration).

CONCLUSION

Even in tooth displacement conditions, vibration significantly reduced SFF, KFF, SSP amplitude, and increased SPP frequency in both PSLB and ASLB. However, in vivo studies would be needed to confirm the clinical significance.

Frictional resistance of self-ligating versus conventional brackets in different bracket-archwire-angle combinations

Objective

To compare the influence of archwire material (NiTi, beta-Ti and stainless steel) and brackets design (self-ligating and conventional) on the frictional force resistance.

Material and Methods

Two types of brackets (self-ligating brackets - Smartclip, 3M/Unitek - and conventional brackets - Gemini, 3M/Unitek) with three (0, 5, and 10 degrees) slot angulation attached with elastomeric ligatures (TP Orthodontics) were tested. All brackets were tested with archwire 0.019"x0.025" nickel-titanium, beta-titanium, and stainless steel (Unitek/3M). The mechanical testing was performed with a universal testing machine eMIC DL 10000 (eMIC Co, Brazil). The wires were pulled from the bracket slots at a cross-head speed of 3 mm/min until 2 mm displacement.

Results

Self-ligating brackets produced significantly lower friction values compared with those of conventional brackets. Frictional force resistance values were directly proportional to the increase in the bracket/ wire angulation. With regard to conventional brackets, stainless steel wires had the lowest friction force values, followed by nickel-titanium and beta-titanium ones. With regard to self-ligating brackets, the nickel-titanium wires had the lowest friction values, significantly lower than those of other materials.

Conclusion

even at different angulations, the self-ligating brackets showed significantly lower friction force values than the conventional brackets. Combined with nickel-titanium wires, the self-ligating brackets exhibit much lower friction, possibly due to the contact between nickel-titanium clips and wires of the same material.

Comparison of the frictional resistance between archwire and different bracket system: An in vitro study

BACKGROUND AND OBJECTIVES

The purpose of this study is to evaluate the frictional resistance generated by conventional stainless steel, radiance ceramic bracket, self-ligating and composite brackets using a 0.019 × 0.025 stainless steel straight length wires in a 022 slot and to select brackets based on their frictional characteristic.

METHODOLOGY

In order to conduct this study, four different types of bracket system were selected of the mclaughlin-bennet-trevesi (MBT) discipline. They are Group 1 - stainless steel, Group 2 - composite bracket Group 3 - (American Orthodontics) radiance ceramic bracket Group 4 - self-ligating bracket (SLB) (Empower). In this study, five maxillary brackets of an arch of each type were used. All brackets are 0.022 × 0.028 in preadjusted edgewise appliance which simulates the dental arch. Five brackets were bonded to a stainless steel bar of dimension 150 mm × 25 mm × 3 mm. The bracket-arch wire units were submitted to mechanical test with an Instron universal testing machine 3365. A testing apparatus or holding jig was designed to hold the bracket during the mechanical test. Each sample was pulled at a speed of 6 mm for 1 min. Descriptive statistical information including mean and standard deviation of maximum friction force was calculated for each bracket wire combination.

INTERPRETATION AND CONCLUSION

The SLB has the least friction among the four groups. The ceramic bracket showed the highest friction followed by stainless steel bracket, composite bracket, and SLB.

Efficacy of Super Slick elastomeric modules in reducing friction during sliding: a comparative in vitro study

AIM

To evaluate and compare the frictional resistance produced by Super Slick modules during sliding with four different types of brackets and four ligature types both in conventional and figure-of-8 ligation method with saliva as lubricant.

MATERIALS AND METHODS

The frictional resistance was evaluated by using four different ligatures on 0.019" × 0.025" stainless steel (SS) archwires using four different brackets using an universal testing machine with unstimulated saliva as a lubricant. Mean and SD values were calculated. Data was statistically analyzed using analysis of variance ANOVA with post hoc test.

RESULTS

The results showed that self-ligating brackets produced least frictional forces. Among all other tested combinations,Tefon-coated SS ligatures in ceramic with metal slot brackets produced least coefficient of static and kinetic friction and full ceramic brackets ligated with Super Slick elastomeric modules demonstrated the highest, with other combinations falling in between.

CONCLUSION

Super Slick elastomeric modules, produced highest coefficient of both static and kinetic friction with the conventional and figure-of-8 ligation technique even in wet conditions using natural fresh human saliva.

CLINICAL SIGNIFICANCE

Both static and kinetic frictional resistance play an important role during sliding mechanics. Various factors have been attributed for friction. However, bracket type, archwire material, type of ligature and method of ligation are important variables. Recently polymeric coated slick elastomeric modules were introduced with the claim that they produce very low frictional forces in wet condition. Contrary to the claim made by the manufacturers of Super Slick elastomeric modules, they produced highest coefficient of both static and kinetic friction with the conventional and figure-of-8 ligation technique.

A comparative in-vivo evaluation of the alignment efficiency of 5 ligation methods: A prospective randomized clinical trial

Objectives:

To conduct a prospective randomized study comparing the efficiency of 5 different ligation systems (ELL; elastomeric ligature, SSL; stainless steel ligature, LL; leone slide ligature, PSL; passive self-ligation and ASL; active self-ligation) over the duration of mandibular crowding alleviation.

Materials and Methods:

Fifty consecutive patients (54.2% male, 45.8% female; mean age: 16.69 years) satisfying the inclusion criteria were randomly allocated to 5 ligation groups with an equal sample size of 10 per group. The 5 groups received treatment with 0.022-inch MBT pre-adjusted edge-wise technique (ELL: Gemini 3M Unitek, SSL: Gemini 3M Unitek, LL: Gemini 3M Unitek, PSL: SmartClip 3M Unitek and ASL: In-Ovation R Euro GAC International). The models and cephalograms were evaluated for anterior arch alignment, extraction space closure, and lower incisal inclinations at pre-treatment T₁ and at the end of initial alignment T₂. Analysis of variance (ANOVA) and Post-hoc tests were used for data analysis.

Results:

Forty-eight participants completed the study, and SL systems showed a significant difference over CL groups in time to alignment, passive space closure, and incisal inclination. Multiple regression showed a reduction of 5.28 days in time to alignment by changing the ligation group in the order of ELL to ASL group and 1 mm increase in initial irregularity index increases time to alignment by 11.68 days.

Conclusion:

Self-ligation brackets were more efficient than conventional ligation brackets during initial leveling and alignment.

Effects of third-order torque on frictional force of self-ligating brackets

OBJECTIVE

To investigate the effects of third-order torque on frictional properties of self-ligating brackets (SLBs).

MATERIALS AND METHODS

Three SLBs (two passive and one active) and three archwires (0.016 × 0.022-inch nickel-titanium, and 0.017 × 0.025-inch and 0.019 × 0.025-inch stainless steel) were used. Static friction was measured by drawing archwires though bracket slots with four torque levels (0°, 10°, 20°, 30°), using a mechanical testing machine (n  =  10). A conventional stainless-steel bracket was used for comparison. RESULTS were subjected to Kruskal-Wallis and Mann-Whitney U-tests. Contact between the bracket and wire was studied using a scanning electron microscope.

RESULTS

In most bracket-wire combinations, increasing the torque produced a significant increase in static friction. Most SLB-wire combinations at all torques produced less friction than that from the conventional bracket. Active-type SLB-wire combinations showed higher friction than that from passive-type SLB-wire combinations in most conditions. When increasing the torque, more contact between the wall of a bracket slot and the edge of a wire was observed for all bracket types.

CONCLUSIONS

Increasing torque when using SLBs causes an increase in friction, since contact between the bracket slot wall and the wire edge becomes greater; the design of brackets influences static friction.

Non-surgical, non-extractive treatment of a severe class III malocclusion in permanent dentition: follow-up of a case 24 years posttreatment

This case shows a patient who had presented a severe Class III malocclusion, both maxillary and mandibular crowding and an impacted canine: she is now 24 years posttreatment. She was treated, in permanent dentition, by proclination of both maxillary and mandibular incisors, expansion of the maxillary arch and of the mandibular intercanine width and disinclusion of the impacted canine. At debonding, she presented well-aligned arch forms, a centered midline and a pleasant smile. Twenty-four years after treatment, her records show that the occlusion has remained stable. The use of wires of almost full thickness helped effectively control incisor torque, thus keeping the teeth inside the cortical bone and limiting the expected periodontal problems.

Effect of applied moment on resistance to sliding among esthetic self-ligating brackets

OBJECTIVE

To determine the effect of mode of ligation and bracket material on resistance to sliding (RS) by comparing various esthetic brackets of conventionally ligated and self-ligating (SL) designs under an increasing applied moment in the second-order dimension.

MATERIALS AND METHODS

Eight different commercially available esthetic brackets of SL and conventional elastomeric-ligated (CL) designs were mounted on a testing apparatus to simulate canine retraction using sliding mechanics and the application of a moment on 0.019″×0.025″ stainless steel archwire. The samples examined were the CL brackets Clarity™, Inspire Ice™, SpiritMB™, and Mystique™, and the SL brackets ClaritySL™, In-OvationC™, In-OvationR™, and Smartclip™. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets. Descriptive measures and one-way analysis of variance were used to calculate means and statistical differences among the bracket types.

RESULTS

The CL monocrystalline bracket displayed significantly greater (P < .05) RS than all other brackets tested. Among the other brackets, the range of RS values was 145.8-191.7 g and 291.9-389.2 g at moments of 2000 g-mm and 4000 g-mm, respectfully, though these differences were not significant (P < .05). All brackets tested displayed greater levels of RS (P < .05) at 4000 g-mm than at 2000 g-mm.

CONCLUSION

With the exception of the CL monocrystalline bracket, all brackets displayed comparable amounts of RS regardless of mode of ligation or bracket slot material.

Systematic review on self-ligating vs. conventional brackets: initial pain, number of visits, treatment time

OBJECTIVE

Meta-analysis of differences between conventional and self-ligating brackets concerning pain during tooth movement, number of patient visits, total treatment duration, and ligation times.

MATERIALS AND METHODS

Online search in Medline, Embase, and Central focused on randomized clinical trials and controlled clinical studies published between 1996 and 2012.

RESULTS

Four studies on pain met our inclusion criteria, two on the number of appointments, two on overall treatment time but none on ligation times. Pain levels did not differ significantly between patients treated with conventional or self-ligating brackets after 4 h, 24 h, 3 and 7 days. The number of appointments and total treatment times revealed no significant differences between self-ligating and conventional brackets.

CONCLUSION

The lack of significant overall effects apparent in this meta-analysis contradicts evidence-based statements on the advantages of self-ligating brackets over conventional ones regarding discomfort during initial orthodontic therapy, number of appointments, and total treatment time. Due to the limited number of studies included, further randomized controlled clinical trials are required to deliver more data and to substantiate evidence-based conclusions on differences between the two bracket types considering orthodontic pain, number of visits, treatment, and ligation times.

Opening and closure forces of sliding mechanisms of different self-ligating brackets

Self-ligating brackets engage the wire by means of a slide mechanism. Forces that have to be applied to open and close the sliding mechanism of brackets are still unknown.

OBJECTIVE

The aim of this study was to measure and compare the opening and closure forces of different self-ligating brackets.

MATERIAL AND METHODS

Three different stainless steel self-ligating brackets (Carriere LX, Ortho Organizers; F1000, Leone; Damon Q, Ormco) were tested. For each different bracket, 20 maxillary right central incisors and 20 mandibular right central incisors were used. Opening and closure forces were measured using an Instron Universal Testing Machine. Statistical analysis was performed and ANOVA and Tukey tests were carried out.

RESULTS

Opening forces were registered between 1.1 N and 5.6 N, whereas closure forces were recorded between 1.57 N and 4.87 N. Significant differences were detected among the different brackets and between the two prescriptions tested.

CONCLUSION

The knowledge of different opening and closure forces of self-ligating brackets can help the orthodontist in the clinical management of these devices.

Self-ligating fully customized lingual appliance and chair-time reduction: a typodont study followed by a randomized clinical trial

In this study, we tested the hypothesis that self-ligation can reduce the chair time necessary for inserting and removing the archwire in a fully customized, multi-bracket, orthodontic, lingual appliance. A permuted-block, randomized trial design was employed to treat seven patients, each with Incognito(®) lingual appliances and Harmony(®) self-ligating lingual appliances. Three operators (a third year resident in orthodontics, an orthodontic specialist, and an experienced lingual orthodontist) were instructed, and they were allowed to familiarize themselves with two typodonts. Next, the operators were asked to insert and remove a.014 NiTi customized archwire for each patient, and they were timed. The time required for removing and inserting archwires decreased proportionally with operator experience: it was shorter with self-ligating appliances (114.82±18.06 seconds versus 595.83±289.09 seconds, P < 0.001) and when testing the typodonts' performances (480.61±285.74 seconds versus 518.65±296.97 seconds, P < 0.001). However, differences between operators were smaller when using typodonts (31.77±21.19 seconds versus 43.87±27.06 seconds, P < 0.001) and with self-ligation (15.17±9.29 seconds versus 45.37±25.44 seconds, P < 0.001). In vivo performance improved after typodont training, allowing for difference reductions between operators. Lingual self-ligation appears to require less hands-on ability and training of the orthodontist, for reduction of chair time.

Self-ligating vs conventional brackets as perceived by orthodontists

OBJECTIVE

To determine if there are significant clinical differences between self-ligating brackets (SLB) and conventional brackets (CB) during orthodontic treatment, as perceived by orthodontists.

MATERIALS AND METHODS

A survey was developed and distributed to evaluate how SLB compare to CB in terms of orthodontists' perceptions (n  =  430).

RESULTS

SLB were preferred during the initial stage of treatment based on the shorter adjustment appointments and faster initial treatment progress they provided (P < .0001). On the other hand, practitioners preferred CB during the finishing and detailing stages of treatment (P < .0001). CB were also preferred over SLB because they were cheaper and resulted in fewer emergency appointments.

CONCLUSIONS

The orthodontists' preference was significantly influenced by (1) the proportion of patients treated with SLB (P < .0001), (2) the number of cases it took them to become accustomed to SLB (P < .0001), and (3) the average appointment intervals associated with SLB (P < .0001).

A comparison of resistance to sliding of self-ligating brackets under an increasing applied moment

OBJECTIVE

To test the null hypotheses that at clinically relevant amounts of applied moment, there are no differences in the amount of resistance to sliding (RS) between self-ligating (SL) and conventionally ligated (CL) brackets on both stainless steel (SS) and nickel-titanium (NT) archwire.

MATERIALS AND METHODS

Three different SL brackets and one CL bracket, all 0.022″ slot, were tested on a custom-built device to simulate canine retraction mechanics in the second-order dimension. The setup allowed for simultaneous and continuous measurement of RS and applied moment at the bracket-archwire interface. The brackets tested were Damon3, In-Ovation R, Smartclip, and Victory, all of which were tested with 0.019″ × 0.025″ SS and NT archwires. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets and both archwire types. Descriptive measures, analysis of variance, and Tukey-Kramer post-test comparisons were used to calculate results.

RESULTS

All brackets displayed a greater amount of RS with NT than with SS archwires. At the higher moment levels (4000 g-mm), no significant reduction in RS was found between CL and SL brackets on both SS and NT archwires. At lower levels of applied moment (2000 g-mm), reductions in RS of 18% (42.7 g) and 18% (38.5 g) were found between the CL bracket and the best performing SL bracket on NT and SS, respectively.

CONCLUSION

At low values of applied moment, some statistical differences were found; however, in general, the differences in RS amongst the various SL and CL brackets tested may not be clinically relevant.

Desmistificando os braquetes autoligáveis

Atualmente, os braquetes autoligáveis têm sido associados a tratamentos mais rápidos e eficazes, o que desperta a curiosidade em compará-los ao sistema convencional. Ao contrário dos braquetes tradicionais, os autoligáveis não necessitam de ligaduras, sejam elásticas ou metálicas. A literatura é farta em concluir que essa característica diminui, ostensivamente, a resistência do atrito durante as mecânicas de deslize. Além disso, existem alegações sobre a dimimuição da necessidade de extrações e de expansão maxilar com o uso desses acessórios. Portanto, o objetivo dessa revisão de literatura foi buscar os mais novos estudos a respeito dos aparelhos autoligáveis atualmente utilizados nos tratamentos ortodônticos, confirmando ou retificando as especulações vigentes.

Maxillary canine retraction with self-ligating and conventional brackets

OBJECTIVE

To measure space closure during the retraction of upper permanent canines with self-ligating and conventional brackets.

MATERIALS AND METHODS

Fifteen patients who required maxillary canine retraction into first premolar extraction sites as part of their orthodontic treatment completed this study. In a random split-mouth design, the retraction of upper canines was performed using an elastomeric chain with 150 g of force. The evaluations were performed in dental casts (T0, initial; T1, 4 weeks; T2, 8 weeks; T3, 12 weeks). The amount of movement and the rotation of the canines as well as anchorage loss of the upper first molars were evaluated.

RESULTS

There was no difference between self-ligating and conventional brackets regarding the distal movement of upper canines and mesial movement of first molars (P > .05). Rotation of the upper canines was minimized with self-ligating brackets (P < .05).

CONCLUSION

Distal movement of the upper canines and anchorage loss of the first molars were similar with both conventional and self-ligating brackets. Rotation of the upper canines during sliding mechanics was minimized with self-ligating brackets.

Systematic review of self-ligating brackets

INTRODUCTION

Self-ligating brackets have been gaining popularity over the past several decades. Various advantages for these systems have been claimed. The purposes of this systematic review were to identify and review the orthodontic literature with regard to the efficiency, effectiveness, and stability of treatment with self-ligating brackets compared with conventional brackets.

METHODS

An electronic search in 4 data bases was performed from 1966 to 2009, with supplemental hand searching of the references of retrieved articles. Quality assessment of the included articles was performed. Data were extracted by using custom forms, and weighted mean differences were calculated.

RESULTS

Sixteen studies met the inclusion criteria, including 2 randomized controlled trials with low risk of bias, 10 cohort studies with moderate risk of bias, and 4 cross-sectional studies with moderate to high risk of bias. Self-ligation appears to have a significant advantage with regard to chair time, based on several cross-sectional studies. Analyses also showed a small, but statistically significant, difference in mandibular incisor proclination (1.5 degrees less in self-ligating systems). No other differences in treatment time and occlusal characteristics after treatment were found between the 2 systems. No studies on long-term stability of treatment were identified.

CONCLUSIONS

Despite claims about the advantages of self-ligating brackets, evidence is generally lacking. Shortened chair time and slightly less incisor proclination appear to be the only significant advantages of self-ligating systems over conventional systems that are supported by the current evidence.

Self-ligating brackets in orthodontics. A systematic review

OBJECTIVE

To evaluate the clinical differences in relation to the use of self-ligating brackets in orthodontics.

MATERIALS AND METHODS

Electronic databases were searched; no restrictions relating to publication status or language of publication were applied. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) investigating the influence of bracket type on alignment efficiency, subjective pain experience, bond failure rate, arch dimensional changes, rate of orthodontic space closure, periodontal outcomes, and root resorption were selected. Both authors were involved in study selection, validity assessment, and data extraction. Disagreements were resolved by discussion.

RESULTS

Six RCTs and 11 CCTs were identified. Meta-analysis of the influence of bracket type on subjective pain experience failed to demonstrate a significant advantage for either type of appliance. Statistical analysis of other outcomes was unfeasible because of inadequate methodological design and heterogenous designs.

CONCLUSIONS

At this stage there is insufficient high-quality evidence to support the use of self-ligating fixed orthodontic appliances over conventional appliance systems or vice versa.

Frictional Resistance in Self-Ligating Orthodontic Brackets and Conventionally Ligated Brackets

Objective: To compare the amount of expressed frictional resistance between orthodontic self-ligating brackets and conventionally ligated brackets in vitro as reported in the literature.

Methods: Several electronic databases (Medline, PubMed, Embase, Cochrane Library, and Web of Science) were searched without limits. In vitro studies that addressed friction of self-ligating brackets compared with conventionally ligated brackets were selected and reviewed. In addition, a search was performed by going through the reference lists of the selected articles to identify any paper that could have been missed by the electronic searches.

Results: A total of 70 papers from the electronic database searches and 3 papers from the secondary search were initially obtained. After applying the selection criteria, only 19 papers were included in this review. A wide range of methods were applied.

Conclusions: Compared with conventional brackets, self-ligating brackets produce lower friction when coupled with small round archwires in the absence of tipping and/or torque in an ideally aligned arch. Sufficient evidence was not found to claim that with large rectangular wires, in the presence of tipping and/or torque and in arches with considerable malocclusion, self-ligating brackets produce lower friction compared with conventional brackets.