Torque efficiency of square and rectangular archwires into 0.018 and 0.022 in. conventional brackets

Occlusal outcome of orthodontic treatment: a systematic review with meta-analyses of randomized trials

BACKGROUND

Several appliances or treatment protocols are marketed to either patients or orthodontists as being associated with improved orthodontic outcomes. However, clinical decision-making should be based on robust scientific evidence and not marketing claims or anecdotal evidence.

OBJECTIVE

To identify appliances/protocols being associated with improved outcomes of fixed appliance treatment.

SEARCH METHODS

Unrestricted literature searches in seven databases/registers for human studies until March 2024.

SELECTION CRITERIA

Randomized or quasi-randomized clinical trials on human patients of any age, sex, or ethnicity receiving comprehensive orthodontic treatment with fixed appliances and assessing occlusal outcome with either the Peer Assessment Rating (PAR) or the American Board of Orthodontics-Objective Grading System (ABO-OGS) index.

DATA COLLECTION AND ANALYSIS

Duplicate/independent study selection, data extraction, and risk of bias assessment with the Cochrane RoB 2 tool. Random-effects meta-analyses of averages or mean differences with their 95% Confidence Intervals (CI), followed by meta-regression/subgroup/sensitivity analyses and assessment of the quality of clinical recommendations with the Grades of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Data from 20 small- to moderately-sized trials covering 1470 patients indicated that orthodontic treatment with fixed appliances is effective and results on average in a final PAR score of 6.0 points (95% CI 3.9-8.2 points), an absolute PAR reduction of 23.0 points (95% CI 15.6-30.4 points), a % PAR reduction of 82.6% (95% CI 70.8%-94.4%), and an absolute ABO-OGS score of 18.9 points (95% CI 11.7-26.2 points). However, very high between-study heterogeneity (I2 > 75%) was seen for both PAR and ABO-OGS. Extraction treatment was associated with significantly better occlusal outcome than non-extraction treatment with ABO-OGS (12.9 versus 16.6 points; P = .02). There was no statistically significant difference in occlusal outcome with (i) 0.018″-slot or 0.022″-slot brackets; (ii) customized or prefabricated brackets; (iii) anchorage reinforcement with temporary anchorage devices; (iv) use of vibrational adjuncts; and (v) aligners or fixed appliances (P > .05 in all instances), while small benefits were seen with indirectly bonded brackets.

CONCLUSIONS

Considerable between-study heterogeneity exists in the reported occlusal outcome of fixed appliance treatment, and different appliances or adjuncts have little effect on this. Standardization and/or automatization of the scoring procedures for PAR and ABO-OGS might help to improve consistency and reliability of outcome measurement in orthodontic trials.

REGISTRATION

PROSPERO (CRD42024525088).

Biomechanical effects of a new crimpable gate spring combined with conventional rectangular archwires for torque adjustment of individual anterior teeth : A comparative finite element study

OBJECTIVE

Precise root torque adjustment of anterior teeth is indispensable for optimizing dental esthetics and occlusal stability in orthodontics. The efficiency of traditional rectangular archwire manipulation within bracket slots seems to be limited. The crimpable gate spring, a novel device, has emerged as a promising alternative. Yet, there is a paucity of guidelines for its optimal clinical application. This study used finite element analysis (FEA) to investigate the biomechanical impact of the gate spring on torque adjustment of individual anterior teeth and to elucidate the most effective application strategy.

METHODS

A FEA model was constructed by a maxillary central incisor affixed with an edgewise bracket featuring a 0.022 × 0.028 inch (in) slot. A range of stainless steel rectangular archwires, in conjunction with a gate spring, were modeled and simulated within the bracket slots. A control group utilized a conventional rectangular wire devoid of a gate spring. Palatal root moments were standardized to 9, 18, and 36 Nmm for both experimental and control groups.

RESULTS

The gate spring significantly amplified palatal root movement, notably with the 0.019 × 0.025 in archwire. However, this was accompanied by an increase in stress on the tooth and periodontal ligament, particularly in the cervical regions. The synergistic use of a 0.019 × 0.025 in rectangular archwire with a gate spring in a 0.022 × 0.028 in bracket slot was identified as most efficacious for torque control of individual anterior teeth.

CONCLUSIONS

The gate spring is a viable auxiliary device for enhancing torque adjustment on individual teeth. However, caution is advised as excessive initial stress may concentrate in the cervical and apical regions of the periodontal ligament and tooth.

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.

Assessment of Various Archwire Materials and Their Impact on Orthodontic Treatment Outcomes

Aim Orthodontic treatment relies heavily on the mechanical properties and surface characteristics of archwire materials to achieve optimal outcomes. This study aimed to comprehensively evaluate the mechanical properties, including tensile strength, yield strength, and modulus of elasticity, as well as the surface characteristics, such as surface roughness and frictional properties, of different archwire materials. Methods Four types of archwire materials, stainless steel, nickel-titanium (NiTi), beta-titanium, and esthetic archwires, were subjected to mechanical testing and surface analysis, with 31 in each group. Tensile testing was conducted to determine the maximum tensile strength, yield strength, and elastic modulus of each material. Surface roughness analysis was performed using profilometry techniques, and frictional properties were evaluated using an orthodontic friction testing apparatus. Results Stainless steel exhibited the highest tensile strength (900 N), followed by beta-titanium (850 N), NiTi (800 N), and esthetic archwire (750 N). Stainless steel also demonstrated the highest yield strength (780 N), followed by beta-titanium (740 N), NiTi (710 N), and esthetic archwire (650 N). The modulus of elasticity was the highest for stainless steel (200 GPa), followed by beta-titanium (170 GPa), NiTi (150 GPa), and esthetic archwires (120 GPa). Surface roughness was lowest in stainless steel archwires (mean Ra value of 0.25 µm), leading to reduced frictional resistance, whereas esthetic archwires exhibited the highest surface roughness (mean Ra value of 0.40 µm) and frictional forces. Significant differences in the mechanical properties and surface characteristics were observed among the materials (p < 0.05). Conclusions The choice of archwire material significantly influences orthodontic treatment outcomes by affecting the efficiency and effectiveness of tooth movement. Stainless steel and beta-titanium wires are ideal for high-stress applications, providing the robust mechanical strength necessary for complex movements. In contrast, NiTi wires, with their superelasticity, offer consistent and gentle forces, enhancing patient comfort and accelerating the alignment phase. Esthetic archwires, while visually appealing, often compromise mechanical performance, potentially prolonging treatment duration.

Comparison of torque expression among passive self-ligating brackets with different slot depths: An in vitro study

INTRODUCTION

The aim of this study was to assess the interaction between a 0.019×0.025-inch (″) stainless steel archwire and two types of passive self-ligating brackets with the same slot height (0.022″) and different slot depths (0.028″ and 0.026″, and to measure the archwire/slot play as well as to compare the torque expression with archwire torsions of 12°, 24°, and 36°.

MATERIAL AND METHODS

An experimental device was developed along with a universal testing machine to measure torque expression in two types of brackets with 0.028″ and 0.026″ slot depths. Analysis of variance (ANOVA) and Tukey's test were performed to identify the differences between groups.

RESULTS

The 0.026″ slot bracket presented greater archwire/slot play when compared to the 0.028″ bracket. Torque expression with torsions of 24° and 36° were significantly higher in the 0.028″ depth brackets when compared to the 0.026″ depth brackets.

CONCLUSION

The 0.022″×0.026″ passive self-ligating brackets attached with a 0.019″×0.025″ stainless steel archwire provided no greater torque control when compared to 0.022″×0.028″ passive self-ligating brackets.

Comparing Torque Transmission of Different Bracket Systems in Combination with Various Archwires Considering Play in the Bracket Slot: An In Vitro Study

This study aims to examine the play between various archwires and bracket systems, exploring potential variations in angle values for specific torque and torque values for a given angle along different bracket systems. Therefore, seven brackets systems were evaluated in conjunction with different stainless steel archwires of varying dimensions (0.016″ × 0.022″, 0.018″ × 0.025″, and 0.019″ × 0.025″). Biomechanical behavior during torque development and transmission was assessed using a six-component force/torque sensor. Torque angles (5-45°) were specified with subsequent torque measurement, and the sequence was reversed by setting the torque (5-30 Nmm) and measuring the angle. A reference measurement with 0 Nmm torque served to evaluate bracket slot play. Bracket play (0 Nmm) during palatal load ranged between 20.06° and 32.50° for 0.016″ × 0.022″ wire, 12.83° and 21.11° for 0.018″ × 0.025″ wire, and 8.39° and 18.73° for 0.019″ × 0.025″ wire. The BioQuick® bracket exhibited the highest play, while Wave SL® and Damon® Q brackets demonstrated the lowest play (p < 0.001). Significant differences (p < 0.001) between the brackets were observed in the torque angles required to achieve torques of 5-20 Nmm. In summary, each bracket system has a different torque transmission, which is of great clinical importance in order to achieve correct torque transmission and avoid complications such as root resorption.

Comparative evaluation of variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element (FE) method: An in-vitro analysis

OBJECTIVE

While using preadjusted brackets, the position of the bracket on the crown is one of the deciding factors that determine the tooth's final tip, torque, height, and rotation. The final tooth position is not optimal if the bracket is placed incorrectly or if the varying crown morphology does not correspond with the bracket design. The present study was conducted to evaluate and compare the variations in torque expression in maxillary incisor and canine using different bracket prescriptions placed at different crown levels by finite element method.

METHODS

For the present study, three-dimensional models of maxillary right central incisor and canine were made using CREO version 4.0 software. CREO is a powerful three-dimensional (3-D) computer-based, computer-aided design (CAD) software developed by Parametric Technology Corporation (PTC) to aid in design processes. Simulation was done to replicate the clinical situation of an active palatal root torque acting on the incisor and canine. The induced palatal movement of root tips and labial movement of crowns tips, overall stress, and von Mises stress generated in the brackets and the total equivalent strains developed in the periodontal ligament (PDL) were calculated, while the values obtained were tabulated and subjected to statistical analysis.

RESULTS

Based on the findings of the present study, the average maximum stress produced in the bracket was calculated as 265.069 Mpa in incisor and 166.742 Mpa in the canine. Likewise, the average of the maximum displacement of root apex observed in the present study was calculated as 0.01401 mm in the incisor and 0.00421 mm in the canine, while the average strain developed in the PDL was calculated as 0.0587 for incisor and 0.0498 for the canine. Furthermore, it was, also, observed that the magnitude of strain developed in the PDL increased with increase in the stress produced by the bracket prescription for both incisor and canine.

CONCLUSIONS

Within the limitations of the present study, it was concluded that the magnitude of displacement of root apex was significantly influenced by bracket prescription and bracket position. Also, the stress developed in the bracket was influenced by bracket prescription and position, while the variation in crown morphology in the incisor and canine played a significant role in the eventual strain developed in the PDL after torque application.

Clinical implementation of axial angulation of incisors in the course of routine fixed appliance treatment - a retrospective cohort study

PURPOSE

To identify clinically relevant factors for changes in axial angulation of incisors during routine fixed appliance orthodontic treatment.

METHODS

A total of 106 patients (grades 1-2 of IOTN, 64 females, 42 males; mean age: 15.5 years) from a private practice and treated with metal or ceramic brackets were included in this retrospective cohort study. The axial angulation of the upper and lower incisors was measured on lateral cephalograms before insertion of the first rectangular 0.016 × 0.022-in NiTi archwire (T0) and at the end of treatment about 8 weeks after insertion of the working 0.019 × 0.025-in stainless steel archwire (T1). Treatment-related changes according to bracket type, initial situation, premolar extraction, angle class, and skeletal vertical configuration were analyzed.

RESULTS

Although statistically significant treatment-related changes were seen for both the upper incisors (+ 1.3°) and the lower incisors (- 5.2°), only in ten patients (9.4%) was the prescribed torque value of 17° for the upper incisors and in no patient for the lower incisors achieved. A negative association between the induced change of axial angulation of incisors and the initial values was detected for the upper incisors as well as for the lower incisors. A comparison of the angle classes revealed significant differences in incisor changes. At the end of therapy, only a slight change for the upper central incisors in patients in angle class I cases and a significantly greater change in patients with angle class II/2 was observed. Cases with premolar extraction ended with lower axial angulation of the incisor than cases without extraction. The individual analysis of possible influencing factors also revealed an association with the vertical skeletal configuration.

CONCLUSIONS

For the first time, the presented data show clinically relevant influencing factors for incisor axial angulation changes of the upper and lower incisors in relation to the torque value of the applied brackets in the course of routine clinical practice. For the orthodontist, it remains mandatory to decide whether a customized system must be individualized in order to achieve individual therapy goals.

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.

Effect of propolis extract on clinical parameters and salivary level of matrix metalloproteinase 8 in periodontitis patients: A randomized controlled clinical trial

Background. Periodontitis is the bacterial-induced inflammation of tooth-supporting structures. Local antibacterial agents are used as adjunctive therapy in the treatment of periodontitis. This study aimed to compare the effect of subgingivally delivered propolis extract (a resin produced by honey bees) with chlorhexidine (CHX) mouthwash on clinical parameters and salivary levels of matrix metalloproteinase 8 (MMP-8) in periodontitis patients.Methods. Twenty-eight periodontitis patients in stage II or III and grade B, who had deep periodontal pockets (≥4 mm) around at least three non-adjacent teeth, were divided into two groups. In the control group, patients were prescribed 0.2% CHX mouthwash twice a day for two weeks. In the 20% propolis hydroalcoholic group, subgingival irrigation was performed twice a week for two weeks. Clinical parameters were measured at baseline and after two months. Salivary samples were collected from the propolis and control groups at baseline and two months later to assess MMP-8 levels using the enzyme-linked immunosorbent assay. Additionally, salivary samples from 12 periodontally healthy subjects were used to determine the normal levels of MMP-8. The data were analyzed using SPSS. P<0.05 was considered the level of significance.Results. In the healthy group, the mean salivary levels of MMP-8 were significantly lower than that in the control and propolis groups at baseline (P<0.001). The results indicated a significant improvement in clinical parameters (P<0.001) in the propolis group compared to the control group, while MMP-8 levels decreased significantly in both groups (P<0.001).Conclusion. Propolis is recommended as adjunctive therapy for periodontitis patients. Clinical trials registration code: IRCT2016122030475N3.

Inclinometer: A new device for measuring intermolar torque and angle

The torque of posterior teeth is of great importance in esthetics and occlusion. In the present article, we introduce a simple but useful device to measure intermolar torque. The device consists of two movable and adjustable arms that lie on the selected molar teeth bilaterally; the graduated plane at the body of the appliance then shows the intermolar torque. This device can measure intermolar torque easily and rapidly, with high validity and at a low cost.

Implications of pretreatment incisor inclinations for the achievement of cephalometric normal values-a study on two patient collectives

PURPOSE

The objective was to clarify whether standardized multibracket therapies-differing only in finishing-wire dimensions (0.016 × 0.022 inch vs. 0.017 × 0.025 inch CNA [Connecticut New Archwire]) and excluding any extraction treatment or additional appliances other than intermaxillary elastics-can produce normal incisor inclinations starting from different baseline inclinations.

METHODS

We analyzed pre- and posttreatment cephalograms of 156 patients (age: 15.6 ± 1.3 years) treated with Roth system (0.018 inch slot). Each archwire group (n = 89 or 67) was divided into subjects with initially retroclined, orthograde, or proclined upper and/or lower incisors (U1, L1). For the resultant 12 subgroups, descriptive statistics were compiled relative to five reference planes (NL, ML, NA, NB, BOP), followed by multiple intragroup (Kolmogoroff-Smirnoff and Wilcoxon signed-rank test) and intergroup (Kruskal-Wallis and Mann-Whitney U test) comparisons relative to NL or ML.

RESULTS

The following intra- (1, 2) and intergroup (3, 4) differences were statistically significant (p ≤ 0.05) in both archwire groups: (1) post- vs. pretreatment inclinations in the subgroups initially retroclined U1, retroclined L1 and orthograde U1, but without normal values being achieved (subgroups retroclined U1, L1) or preserved (subgroup orthograde U1); (2) observed vs. expected alterations for the subgroups initially orthograde and proclined U1 and L1; (3) posttreatment inclinations for the subgroups initially retroclined vs. orthograde L1 and proclined L1; (4) observed alterations for the subgroups initially retroclined vs. proclined U1 and L1, but neither retroclined nor proclined vs. orthograde. Archwire thickness influenced the outcome to only a limited extent under the special circumstances of this study.

CONCLUSION

The bracket/archwire combinations evaluated did not lead to normal incisor inclinations in most cases. Posttreatment values did significantly depend on the pretreatment situation. Most frequently, alterations were protrusive in direction, which notably even included incisors that showed norm values at the outset of treatment. It can be concluded that bracket torque will influence but not dominate incisor inclinations.

Comparison of multiforce nickel-titanium wires to multistrand wires without force zones in bending and torque measurements

PURPOSE

The aim was to compare rectangular multiforce nickel-titanium (NiTi) wires to rectangular wires with only one force zone. Both types of wires are primarily intended for use during the levelling phase of orthodontic treatment. Thus, basic mechanical properties were examined by means of a three-point bending test. Torque expression, which is dependent on both wire parameters and interslot distances, was analyzed using the Orthodontic Measurement and Simulation System (OMSS).

MATERIAL/METHODS

Four multizone products were tested: DuoForce™ (Forestadent, Pforzheim, Germany), TriTanium™ (American Orthodontics, Sheboygan, WI, USA), Triple Force™ (ODS, Kisdorf, Germany), Bio-Active™ (GC, Breckerfeld, Germany), and two multistrand products without force zones: a nine-strand NiTi, TurboWire™ (Ormco, Orange, CA, USA) and an eight-strand stainless steel (SS) wire, Multibraid™ (GAC, Dentsply Sirona, York, PA, USA). All the wires had the dimension 0.40 mm × 0.56 mm (0.016 inch × 0.022 inch) except the nine-strand NiTi wire TurboWire™, which had a dimension of 0.43 mm × 0.65 mm (0.017 inch × 0.025 inch). Six different bracket systems in the 0.018 inch slot system were chosen: the conventional brackets discovery® and discovery® smart (Dentaurum, Ispringen, Germany), the active self-ligating brackets InOvation™ and InOvation™ mini (GAC, Dentsply Sirona, York, PA, USA) and the passive self-ligating brackets Carrière™ (ODS, Kisdorf, Germany) and BioPassive® (Forestadent, Pforzheim, Germany). The first set-up was a three-point bending test according to DIN EN ISO 15841. For the second experiment, the bracket products glued on a maxilla model were combined with the wire products. The torque moments arising during torqueing of the wires between +20° and -20° were measured in three positions: first incisor, canine and second bicuspid.

RESULTS

Bending tests confirmed variation of the force corresponding to the force zones. The nine-strand NiTi wire TurboWire^TM and the eight-strand SS wire Multibraid™ did not show any variation dependent on the tested area. Torque-moments generated by the multizone wires were higher compared to the braided wires. The nine-strand NiTi wire showed the lowest moments in spite of the higher dimension. As expected, increasing the interbracket distance reduced the torque moments.

CONCLUSION

The tests verified the existence of multiple force zones in the NiTi wires for forces and moments, respectively. As the torque-moments arising from the multizone wires were rather high, it is not recommended to use these wires as a first "leveling wire" in orthodontic treatment, especially in extremely crowded cases.

Incisor and profile alterations in extraction cases treated with standard Edgewise and pre-adjusted appliances: A controlled before-and-after study

BACKGROUND

Even though treatment of Class II malocclusion with premolar extractions and incisor retraction might affect incisor inclination and soft tissue profile, the effects of bracket prescription on this have not been thoroughly assessed.

METHODS

Fifty patients (mean age: 13.6 years; 34% male) receiving extraction-based treatment with either standard Edgewise or pre-adjusted appliances were included. Between-group differences in the incisor inclination assessed with lateral cephalograms were analyzed statistically with linear/logistic regression at 5%.

RESULTS

Treatment-induced changes included retroclination of the upper/lower incisors (-3.0° and -2.0°, respectively), retraction of the upper/lower incisors (-3.4 mm and -1.5 mm, respectively), retraction of the upper/lower lip (-2.1 mm and -2.0 mm, respectively), and enlargement of the nasolabial angle (+1.6°). Analysis of the data adjusting for confounders indicated that the pre-adjusted group, after treatment, had larger inclination of the upper or lower incisors (+3.2° and +4.5°, respectively), more prominent upper incisors relative to the facial plane (+1.3 mm), and smaller interincisal angle (-7.3 or -7.7°). Post-treatment upper incisor inclination fell within the cephalometric norm significantly more in the pre-adjusted than in the standard Edgewise group (odds ratio 4.3; 95% confidence interval 1.1-16.6). No differences were found in lower incisor prominence, upper/lower lip prominence, or nasolabial angle.

CONCLUSIONS

Pre-adjusted appliances were associated with increased inclination of the upper and lower incisors, with more prominent upper incisors, and with more acute interincisal angle after retraction compared with standard Edgewise appliances. However, such differences did not translate in greater retraction of the upper/lower lips and greater nasolabial angle.

Expression of Torque and Its Effect on Various Biological Structures Caused by Varying Archwire Material: A 3D FEM Study

Objective:

Studying torque expression and biomechanical effects of various wires on giving palatal root torque, using finite element (FE) method (FEM).

Conclusion:

TMA wires are most favourable for torquing, in terms of torque expression and susceptibility to root resorption.

Materials and Method:

Geometric model of maxillary right central incisor was developed, using computed tomography (CT) scan. 0.022" × 0.028" Standard edgewise brackets and 10-mm-long stainless steel (SS), titanium molybdenum (TMA) and titanium niobium (TiNb) archwires of dimension 0.019" × 0.025" were modeled and a palatal root torque of 25 degrees was applied on all wires. The angular displacement of the crown and root and nodal displacement at the incisal edge and root apex in y and z axis were analyzed along with stresses on periodontal ligament (PDL), bone, cementum, enamel, and bracket.

Results:

Buccal crown and palatal root movement was seen, which was maximum for SS and least for TMA. Angular displacement was also highest for SS. Compressive stresses were concentrated at the bucco-cervical and linguo-apical regions in the PDL, cementum, and bone and tensile stresses were concentrated in the linguo-cervical regions. In the enamel, the bracket attachment site showed maximum stresses, and slot base showed higher values of stresses than wings. All stress values were highest for SS and least for TMA.

Comparative Evaluation of Dimensional Accuracy, Surface Characteristics, and Load Deflection Attributes of 0.019" × 0.025" Stainless Steel Wires Sourced from Six Different Commercial Houses: An In Vitro Study

Aims & Objectives:

The aim of the study was to evaluate and compare dimensional accuracy, surface characteristics and load deflection attributes of SS wires sourced from six different commercial houses.

Materials & Methods:

0.019” x 0.025” SS wire samples were divided into 6 groups and evaluated and compared for the aforementioned properties. Dimensional accuracy, surface roughness, frictional resistance, load deflection rate and ultimate tensile strength were evaluated and compared.

Results:

Dimensional accuracy did not vary significantly. Surface Profilometry proved 3M Unitek (Group 1) to be the wire with least irregularities. According to SEM, Modern Orthodontics (Group 6) and 3M Unitek (Group 1) in terms of ‘Sa’ and ‘Sq’ respectively had the smoothest surface finish. SS wires sourced from G&H Orthodontics (Group 2) exhibited least frictional resistance. Load deflection rates varied for all the groups for all three parameters under the study. UTS was best for SS wires sourced from Rabbit Force Orthodontics (Group 5).

Conclusion:

No wire from a single commercial house excels in all the parameters that were evaluated, each one having its aces and minuses.

Stainless steel and NiTi torque archwires and apical root resorption

Objective

The amount of apical root resorption when using the torque-segmented archwire (TSA) was investigated as well as the extent and direction of the therapeutically indicated apical movement and the treatment duration.

Materials and methods

The degree of apical root resorption in 18 randomly chosen Class II and Class I patients treated with the TSA, as well as in 18 conventionally treated patients were evaluated using pre- and posttreatment panoramic radiographs. The sagittal and vertical apical movements and inclination changes were determined based on pre- and posttreatment lateral cephalograms. Nonparametric tests were applied to test between treatment groups and steps. The Mann–Whitney U test, Kruskal–Wallis, Pearson correlation and Wilcoxon signed-rank test were applied for statistical analysis (p < 0.05).

Results

The incidence of root resorptions was 89–94.4% in low or moderate level. The relative root–crown ratio (rRCR) was not statistically different between the TSA and control groups except tooth 12. The axis of the incisors in the TSA group was significantly improved. The main direction of movement of the apices of the central incisors was retrusion and extrusion. No interdependence between the amount of resorption and the parameters of treatment duration, extent and direction of apical movement were found.

Conclusion

The results of the study showed that the amount of apical root resorption with the TSA is slight to moderate and can be compared to conventional orthodontic treatment. The TSA is hence a suitable method for applying targeted torques to the incisors.

Comparation of three methods for measuring the Edge Bevel Radius of rectangular orthodontic wires: An in-vitro study

OBJECTIVE

To establish a simplified method for measuring the edge bevel radius of 0.019×0.025-in steel rectangular orthodontic wires, achievable in the clinical environment, and to compare it with the photographic method.

MATERIALS AND METHODS

Aided by the AutoCAD™ 2016 software, the theoretical mathematical relationship was determined between the edge rounding radius and cross-sectional dimensions (height, width, diagonals), through rectangle drawings that represent cross-sections. Two hundred segments (n=20) were obtained from the posterior portions of 100 archwires from 10 brands (Dentaurum™; American-Orthodontics™; GAC™; 3M-Unitek™; Abzil™; Morelli™; Orthometric™; Aditek™; A-Company™; Orthomundi™). The cross-sectional measures of each segment were obtained with a micrometer and a caliper, and the edge bevel radii of these segments were calculated with the use of a mathematical formula. For the "gold standard", the segments were included longitudinally in a phenolic resin cylinder, cross-sectioned, polished, and photographed in scanning electron microscope (SEM). The images were amplified 770× and the radii were measured with an acetate template. The micrometer and caliper measuring methods were subjected to Bland-Altman analysis and compared with the gold standard (SEM), considering ±10μm as the maximum acceptable difference between methods.

RESULTS

In the micrometre measurement, 95% of the differences from the standard were within the limits of agreement (-7.21 and 5.56μm). For the caliper method, 95% of the differences were between -5.46 and 19.83μm, which exceeded the fixed limit ±10μm.

CONCLUSION

The calculation method with micrometre measurements is equivalent to the photographic method, but there is no such equivalence for the caliper measurements.

Torque efficiency of a customized lingual appliance : Performance of wires with three different ligature systems

PURPOSE

Torque control in lingual orthodontics is key to obtain optimal esthetic results. The aim of this in vitro experimental study was to verify the efficiency of the ligature-archwire-slot system in torque control using a customized lingual appliance.

METHODS

An idealized cast with eight extracted human teeth was created and a set of customized lingual brackets was obtained. Tests were performed with the following wires: 0.016″ × 0.022″ nickel-titanium (NiTi), 0.016″ × 0.024″ stainless steel (SS), 0.017″ × 0.025″ βIII titanium (βIIITi), 0.0182″ × 0.0182″ βIIITi, 0.018″ × 0.025″ SS, 0.018″ × 0.025″ NiTi, 0.018″ × 0.025″ βIIITi, and three types of ligatures were tested using a universal testing machine to calculate the efficiency in torque control. A blind statistical analysis was performed.

RESULTS

Based on post hoc multiple comparisons, differences were found for two of the three ligatures when using the 0.016″ × 0.022″ NiTi wires (p < 0.001 for both ligatures). When considering all ligatures, 0.018″ × 0.025″ SS and 0.018″ × 0.025″ βIIITi were significantly different from all other wires (p < 0.001 in all cases). With a moment of 5 Nmm, the 0.016″ × 0.022″ NiTi wire developed median angles of 26.7, 29.8, and 38.7° with the three ligatures, respectively, while the 0.018″ × 0.025″ SS developed median angles of 12.9, 10.7, and 12.7°, respectively.

CONCLUSIONS

The ligature type and geometry did not affect the efficiency of torque control, except for the 0.016″ × 0.022″ NiTi wire. The wires generating the greatest moments were the 0.018″ × 0.025″ SS and 0.018″ × 0.025″ βIIITi.

A randomized clinical trial of the effectiveness of 0.018-inch and 0.022-inch slot orthodontic bracket systems: part 2-quality of treatment

OBJECTIVE

To compare the quality of orthodontic treatment between 0.018-inch and 0.022-inch slot bracket systems.

SUBJECTS AND METHODS

Eligible participants aged 12 years or over were allocated to the 0.018-inch or 0.022-inch slot MBT appliance (3M-Unitek, Monrovia, California, USA) using block randomization in groups of 10. Outcome measures included: 1. ABO cast-radiograph evaluation (CR-EVAL), 2. peer assessment rating (PAR) scores, 3. incisor inclination, and 4. patient perception using the Index of Orthodontic Treatment Need aesthetic component (IOTN AC) and three validated questionnaires before, during and after treatment. Parametric tests [independent samples t-test and two-way analysis of variance (ANOVA)] and non-parametric tests (chi-square with Fisher's exact tests and Mann-Whitney U-test) assessed differences between groups (P < 0.05).

RESULTS

Of the 187 participants randomized (1:1 ratio), 34 withdrew or were excluded (protocol deviations or poor cooperation). There were 77 patients in the 0.018-inch slot group and 76 patients in the 0.022-inch slot group (overall mean age: 19.1 years). Baseline characteristics were similar between groups (P > 0.05). The mean total ABO CR-EVAL scores were 34.7 and 34.5; mean percentage PAR score reduction 74.1 per cent and 77.1 per cent; mean change for maxillary incisor inclination 2.9 degrees and 1.6 degrees and for mandibular incisor inclination 2.7 degrees and 1.4 degrees for the 0.018-inch and 0.022-inch groups, respectively. Improvement in patient perception of aesthetics after treatment was statistically significant for both groups (P < 0.05). However, there were no statistically significant differences between the two treatment groups for ABO CR-EVAL, percentage PAR score reduction, incisor inclination, and patient perception of treatment (P > 0.05). No adverse events were observed during treatment.

LIMITATIONS

It was impossible to blind clinicians or patients to allocation and oral hygiene and periodontal outcomes were not assessed.

CONCLUSIONS

There were no statistically or clinically significant differences in the quality of occlusal outcomes, incisor inclination and patient perception of treatment between 0.018-inch and 0.022-inch slot bracket systems.

REGISTRATION

The trial was registered with ClinicalTrials.gov on 5 March 2014, registration number: NCT02080338.

PROTOCOL

The protocol was published at DOI: 10.1186/1745-6215-15-389.

Torque differences according to tooth morphology and bracket placement: a finite element study

Introduction

Torque of the maxillary incisors is essential in esthetics and proper occlusion, while torque expression is influenced by many factors. The aim of this finite element study was to assess the relative effect of tooth morphology, bracket prescription, and bracket positioning on tooth displacement and developed stresses/strains after torque application.

Methods

A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modelled. The tooth varied in the crown-root angle (CRA) between 156°, 170°, and 184°. An 0.018-inch slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 × 0.025-inch β-titanium wire was modelled. Bracket torque prescription varied between 0°, 12°, and 22°, with bracket placement at the centre of the middle, gingival or incisal third of the crown. A total of 27 models were generated and a buccal root torque of 30° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analysed statistically.

Results

The palatal crown displacement was significantly affected by bracket positioning (up to 94 per cent), while the buccal apex displacement was significantly affected by bracket prescription (up to 42 per cent) and bracket positioning (up to 23 per cent). Strains in the PDL were affected mainly by CRA (up to 54 per cent), followed by bracket positioning (up to 45 per cent). Finally, bracket prescription considerably affected the stresses in the bracket (up to 144 per cent).

Limitations

These in silico results need to be validated in vivo before they can be clinically extrapolated.

Conclusion

Tooth anatomy and the characteristics of the orthodontic appliance should be considered during torque application.

Torque differences due to the material variation of the orthodontic appliance: a finite element study

Background

Torque of the maxillary incisors is crucial to occlusal relationship and esthetics and can be influenced by many factors. The aim of this study was to assess the relative influence of the material of the orthodontic appliance (adhesive, bracket, ligature, and wire) on tooth displacements and developed stresses/strains after torque application.

Methods

A three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modeled. A 0.018-in. slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 x 0.025-in. wire was generated. The orthodontic appliance varied in the material of its components: adhesive (composite resin or resin-modified glass ionomer cement), bracket (titanium, steel, or ceramic), wire (beta-titanium or steel), and ligature (elastomeric or steel). A total of 24 models were generated, and a palatal root torque of 5° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analyzed.

Results

The labial crown displacement and the palatal root displacement of the tooth were mainly influenced by the material of the wire (up to 150% variation), followed by the material of the bracket (up to 19% variation). The magnitude of strains developed in the PDL was primarily influenced by the material of the wire (up to 127% variation), followed by the material of the bracket (up to 30% variation) and the ligature (up to 13% variation). Finally, stresses developed at the bracket were mainly influenced by the material of the wire (up to 118% variation) and the bracket (up to 59% variation).

Conclusions

The material properties of the orthodontic appliance and all its components should be considered during torque application. However, these in silico results need to be validated in vivo before they can be clinically extrapolated.

Electronic supplementary material

The online version of this article (doi:10.1186/s40510-017-0161-5) contains supplementary material, which is available to authorized users.