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

Comparative Analysis of Displacements and Stress Produced by Square and Rectangular Bracket Slot With Incremental Torque: A Finite Element Analysis Study

INTRODUCTION

This study aimed to perform a comparative analysis of stresses and displacements with incremental torque on the maxillary incisors and surrounding cortical bone using conventional metal brackets with rectangular slots and passive self-ligating brackets with square slots using finite element analysis (FEA).

MATERIALS AND METHODS

An in vitro FEA study was conducted, in which a three-dimensional (3D) model of the maxilla was built using ANSYS software version 18 (ANSYS Inc., Canonsburg, PA). The conventional McLaughlin, Bennet, and Trevisi (MBT) bracket (3M Unitek, Monrovia, CA) of 0.022 × 0.028-inch slot with a 0.019 × 0.025-inch rectangular stainless steel (SS) archwire (model 1) was compared with the Pitts 21™ self-ligating bracket system (OC Orthodontics, McMinnville, OR) of 0.021 x 0.21-inch slot with a 0.020 × 0.020-inch square SS archwire (model 2) at incremental torques of 5°, 10°, 15°, and 20°. The von Mises stress was evaluated at the maxillary incisors and surrounding cortical bone. The torque moment, tipping angle, and displacement of the maxillary incisors were also measured and compared between the bracket systems.

RESULTS

The highest torque expression of 13.8 N-mm was observed in model 2, compared to a torque expression of 10.68 N-mm in model 1. The torque expression increased in both models from 0°to 20°. There was a play of 6.2°at 20°torque in model 2, whereas it was 9.32°​​​​​​​play in model 1. The torque expressions were better for the lateral incisors than for the central incisors. Increased incremental torque was associated with increased proclination of the incisors, and this movement was more pronounced for the central incisor and model 1. Furthermore, it was revealed that the stresses on the cortical bone and teeth were higher in model 2 than in model 1.

CONCLUSION

It was concluded that the Pitts 21™ passive self-ligating system produced better torque expression and less play with square SS archwire compared to conventional brackets with rectangular SS archwire.

Comparisons of maxillary incisor retraction effects for patients with first premolar extractions between Damon Q and Invisalign®: A retrospective study

Torque control of maxillary incisors is very important in maxillary protrusion patients with first premolars extraction, but the efficacy of maxillary incisor retraction of clear aligners is still controversial now. This retrospective study was aimed to compare the retraction effects between Damon Q and Invisalign® appliances in patients with first premolar extractions. 59 patients (33 cases with Damon Q and 26 cases with Invisalign®) with first premolar extraction were selected in this study. Subsequently, patients of each group were allocated into three subgroups according to the pretreatment value of U1-NA (°). The retraction effects of maxillary incisors and upper lips were accessed by the variations of cephalometric, overbite and overjet measurements. Treatment duration with Invisalign® (31.4 ± 6.4 months) was longer than Damon Q (27.7 ± 6.3 months) (P = .03). The angular measurements, U1-NA (°) and U1-SN (°) showed more lingual crown inclinations in Invisalign® group than Damon Q group (P ≤ .04). When evaluating linear measurements, the retractions of the maxillary incisors and upper lip positions showed no significant differences (P ≥ .13). Invisalign® group also showed more lingual crown retractions and labial root deviations compared to Damon Q group in subgroup Ⅲ (P ≤ .037). As regards to the molar relationship, Invisalign® displayed less Class Ⅰ molar relationship than Damon Q group. The increased overbite of anterior incisors was also showed in the Invisalign® treatment group (P ≤ .047). Invisalign® was not sufficiently effective in retracting maxillary incisors compared with Damon Q appliances. Invisalign® led to more lingual inclination movement and increased overbite.

Comparative assessment of dental and basal arch dimensions of passive and active self-ligating versus conventional appliances : A randomized clinical trial

PURPOSE

In this parallel, three-arm, single-center randomized trial, the dental and basal arch dimensions after orthodontic treatment using conventional brackets and passive and active self-ligating (SL) brackets were compared.

METHODS

Patients needing comprehensive orthodontic treatment were randomly allocated to the active SL, passive SL, or conventional brackets (control) group. All patients were treated with a standardized arch wires sequence. Eligibility criteria included class I malocclusion in the permanent dentition, crowding (4-6 mm), and adequate oral hygiene. The primary outcome was intermolar width, based on cone beam computed tomography (CBCT) scans. Secondary outcomes were maxillary and mandibular widths in the canines and premolars regions, dental arch depth, buccolingual inclination, and alignment duration. Blinding of outcome assessment was implemented. Patients were followed every 4 weeks until insertion of the stainless steel 0.019 × 0.025 wire. Mean values were computed from CBCT sections, and data were analyzed using a one-way analysis of variance.

RESULTS

In all, 66 patients (ages 18-25 years) were randomized into a 1:1:1 ratio; 7 patients dropped out before treatment initiation. Examining dental arch dimensions in the canine and premolar regions showed that expansion of the maxillary dental arch was greatest in the passive SL brackets group, less in the active SL brackets group, and lowest in the control group (P < 0.01). Changes in maxillary intermolar width between the three groups were not significant, and changes in basal arch dimensions, depth of dental and basal arches, buccolingual inclination, and alignment duration were similar in the three groups.

CONCLUSIONS

Self-ligating brackets were not more effective than conventional brackets when examining intermolar width, basal transverse dimensions, depth of the arch, and alignment duration.

Friction Force Adjustment by an Innovative Covering System Applied with Superelastic NiTi Brackets and Wires-An In-Vitro Study

The aim of this study was the investigation of polymeric coverings to adjust frictional forces between V-shaped wires and brackets, both made of superelastic NiTi. Adjustment of frictional forces is relevant for certain stages during orthodontic therapy. Coverings able to generate frictional forces when assembled to such brackets are additively manufactured. Six different internal widths of coverings were examined in three different environments: dry condition at room temperature (RT) or body temperature (BT), or artificial saliva (AS) at RT. The different coverings significantly affected the frictional forces for all media (p < 0.001). A correlation between internal width of the covering and resulting frictional forces was found. BT and dry environment showed the lowest friction forces for all samples. The highest force was found for two covering types at RT in AS, while the remaining four covering types showed the highest values in dry environment (p < 0.001). Friction could, therefore, be adjusted by variation of bracket covering clipped onto brackets, which is useful for orthodontic therapy. Coverings delivering higher friction provide dental anchorage, while coverings with lower friction can be used for tooth movement or purely esthetic reasons. It was shown that the variation of covering width may be used for adjustment of frictional forces.

Estimation and comparative evaluation of tip and torque values of Saudis for bracket prescription

Objectives

The present study aimed at determining the tip and torque values of the teeth of Saudi adults with normal occlusion to develop orthodontic bracket prescription. In addition, we proposed to compare the results with published data of varied geographical distribution.

Materials and Methods

The study sample consisted of 60 upper and lower study models of Saudi adults (30 males and 30 females) with normal occlusion and a balanced facial profile. Evaluated by experts, the torque and tip of teeth were measured using a torque angulation device. The collected data was analyzed using SPSS (IBM SPSS Inc., version 20, Chicago, IL, USA). The mean, and standard deviation were obtained for each measurement. Paired t-test, Independent t-test and student t-test were used for the comparison at a significant level of (p ≤ 0.05).

Result

The results of torque and tip of teeth for the Saudi adult population showed no significant differences between the right and the left quadrants of the analyzed study sample. In general, there was no significant observed difference between male and female samples, accordingly, the Saudi tip and torque data were combined. However, the comparisons of the combined Saudi data to the published data showed significant differences (p ≤ 0.05).

Conclusion

Statistically Significant differences were found between the combined Saudi data when compared to North American, Italian, African, Japanese, and Indian data. We inferred, that racial differences should be considered when presenting bracket prescriptions.

An Evaluation of Microbial Flora, Alkaline Phosphatase and IL-8 Levels in GCF of Orthodontic Patients with Self-Ligating and Conventional Brackets

PURPOSE

To compare the microbial flora, alkaline phosphatase (ALP) and interleukin-8 (IL-8) levels during orthodontic treatment with self-ligating brackets versus conventional brackets.

PATIENTS AND METHODS

Forty patients were included in this study and distributed equally between two groups. One group received conventional edgewise brackets while the other group received DAMON self-ligating brackets. Periodontal parameters were recorded and biochemical and microbial analyses were conducted before bonding (baseline), and 14, 30, and 45 days after bonding. Paired t-test was performed to estimate the intergroup differences from the baseline at the various time points; unpaired t-test was used for intragroup comparisons.

RESULTS

A significantly higher prevalence of gram-negative as well as gram-positive microorganisms was found in the group with conventional brackets than that with self-ligating brackets. Alkaline phosphatase (ALP) activity and interleukin-8 (IL-8) levels were significantly higher in the gingival crevicular fluid of the group with conventional brackets than that with self-ligating brackets.

CONCLUSION

The conventional bracket-ligature technique exhibited an increase in IL-8 levels, ALP activity, and microbial colonization compared with that of the self-ligature technique. Accordingly, self-ligating brackets are recommended in orthodontic patients to improve periodontal health and minimize damage outcomes of periodontal tissue interventions.

Buccolingual Inclination Effects of Self-Ligating and Conventional Premolar Brackets: A Cone Beam Computed Tomography Study

Objective

This study aimed to compare the effects of passive self-ligating (PSL) and conventional ligating (CL) of brackets on the buccolingual inclination (BLINC) of the maxillary premolars.

Methods

This in vitro study included a PSL bracket group and a CL bracket group. Acrylic teeth on typodonts were aligned using 0.014-inch heat-activated nickel titanium (HANT) (T1) and 0.019×0.025-inch HANT (T2) and 0.021×0.025-inch stainless steel (SS) (T3) archwires in a sequence. Standardized cone beam computed tomography (CBCT) images were taken immediately after each archwire stage. The differences of premolar teeth BLINC values in the 0.019×0.025-inch and 0.014-inch HANT archwires (T2-T1) and 0.021×0.025-inch SS and 0.019×0.025-inch HANT archwires (T3-T2) were compared between PSL and CL groups. The value of p < 0.05 was considered statistically significant.

Results

The BLINC change of the second premolar (SPM) showed a statistically significant difference (p=0.008), but the BLINC change of the first premolar (FPM) (p=0.056) between the groups showed no statistically significant difference during the T2-T1 stage. However, there were statistically significant differences between two groups in the BLINC of the FPM (p=0.032) and SPM (p=0.032) in the T3-T2 stage. The angular changes in the buccal direction in the PSL group were higher than those in the CL group.

Conclusion

The PSL upper premolar brackets used with the 0.021×0.025-inch SS archwire produced more buccal crown movement of the upper PM teeth compared with that of the CL brackets.

Comparative evaluation of the maxillary canine retraction rate and anchorage loss between two types of self-ligating brackets using sliding mechanics

OBJECTIVE:

To evaluate the maxillary canine retraction rate and anchorage loss with active and passive self-ligating brackets (SLBs).

MATERIALS AND METHODS:

The study was conducted on 10 patients whose age ranged from 14–20 years. The patients had minimal to no crowding with a dental protrusion of maxillary incisor that required the extraction of maxillary first premolars and retraction of canines. The maxillary canines had to be in a good alignment and level before treatment to ensure that canine retraction had started from the same point bilaterally. A cone beam computed tomography (CBCT) had been taken for each patient's maxilla before treatment initiation and after complete canine retraction. Using nickel titanium, close-coil spring canine retraction on both sides and the rate of canine movement was measured.

RESULTS:

The patients were checked every 2 weeks to measure the retraction rate and ensure that a constant force (150 g) was being delivered to both canines. The pre- and post-canine retractions CBCT were superimposed to evaluate the pattern and rate of canine movement and anchorage loss. The result of this study showed no statistically significant difference between the two groups.

CONCLUSION:

The type of SLB, either active or passive, does not affect the rate or type of canine movement during its retraction in the orthodontic extraction cases, and the anchorage loss of the upper molars was nearly the same in both type.

Buccolingual Inclination Control of Upper Central Incisors of Aligners: A Comparison with Conventional and Self-Ligating Brackets

OBJECTIVE

The upper incisors torque expression is essential for the orthodontic treatment accuracy. Various orthodontic devices are claimed to have different inclination control capacity. The purpose of this retrospective study was to compare the radiographic buccolingual inclination of upper incisors in patients treated with three different orthodontic techniques.

MATERIAL AND METHODS

Conventional brackets (Victory, 3M), self-ligating appliances (Damon Q, Ormco), and aligners (Invisalign, Align Technology) were tested. Cephalometric data of 25 patients with similar skeletal and dental pretreatment parameters were collected for each technique. Position changes of upper central incisors were assessed with radiographic evaluation before and after therapy. Three different parameters were considered: 11∧SnaSnp, 11∧Ocl and I+ TVL. All variables were measured before (T0) and after (T1) treatment and their variation over treatment was assessed.

RESULTS

When evaluating angular measurements, 11∧SnaSnp and 11∧Ocl angles showed the highest numeric variation with conventional brackets. Lowest values were reported with aligners. However, the differences among various techniques were not significant for both angles (P>0.05). Also I+ TVL linear value variation did not show significant differences among the different groups tested (P>0.05).

CONCLUSION

Conventional multibrackets appliance showed the highest incisal position variations over treatment, but the differences among various groups were not significantly different.

Impact of different rectangular wires on torsional expression of different sizes of buccal tube

Background

Torsions in rectangular wires are the essential part of corrections in the finishing stage of treatment. Moreover the greatest amounts of torques are applied in the molar areas. a clinically effective moment is between 5 and 20 Nmm. In this study we have decided to evaluate the impact of different tube sizes and different dimensions of wires with different modulus of elasticities on the amount torsional bond strength of molar tubes.

Material and Methods

60 human impacted molar teeth were collected. A buccal tube was bonded on the buccal surface of all the samples by using light cured adhesive resin. After that, the teeth were mounted in a hard acrylic block. According to the size of buccal tube and the rectangular wires to be tested 4 groups will be designed. Torsional force was applied by instron machine. The torque angle at 5Nmm and at 20Nmm point will be calculated: which means, how many degrees of torque is required to reach the maximum 20Nmm moment from the minimum 5Nmm.One-way ANOVA was used to compare torque angle in all of the groups.

Results

The least amount of clinically significant angle was 2.2 ᵒ in the 0.017×0.025 SS and the largest amount of it was 23.7 ᵒ in the 0.017×0.025 TMA in 0.018×0.025 slot molar tube. But, this angle was 19.9 ᵒand 13.6 ᵒ in 0.019×0.025 SS and 0.019×0.025 TMA archwire in 0.022×0.028 molar tube.

Conclusions

The 0.017×0.025 SS archwire in 0.018×0.025 molar tube had the lowest clinically significant angle. The largest amount was seen in group 0.017×0.025 TMA in 0.018×0.025 slot molar tube.

Key words: Torsional efficacy, rectangular wires, buccal tubes, torque angle.