Comparison of static friction with self-ligating, modified slot design and conventional brackets

OBJECTIVE: To compare the static frictional forces generated at the bracket/wire interface of stainless steel brackets with different geometries and angulations, combined with orthodontic wires of different diameters. MATERIAL AND METHODS: The frictional forces were evaluated with three different types of metal brackets: a passive self-ligating (SmartClipTM, 3M/Unitek, Monrovia, USA), with a modified slot design (Mini Uni TwinTM, 3M/Unitek, Monrovia, USA) and conventional (Kirium, Abzil, São José do Rio Preto, Brazil). The samples were mounted in a testing device with three different angulations and tested with 0.014" and 0.018" stainless steel wires (American Orthodontics, Sheboygan, USA). The static frictional force was measured using a universal testing machine (DL 500, EMIC®, São José dos Pinhais, Brazil) with a crosshead speed of 1 mm/min. Statistical analysis was performed by two-way ANOVA followed by Bonferroni's post hoc test. RESULTS: There was a significant difference (

Physical and chemical properties of orthodontic brackets after 12 and 24 months: in situ study

Objective: The aim of this article was to assess how intraoral biodegradation influenced the surface characteristics and friction levels of metallic brackets used during 12 and 24 months of orthodontic treatment and also to compare the static friction generated in these brackets with four different methods of the ligation of orthodontic wires. Material and Methods: Seventy premolar brackets as received from the manufacturer and 224 brackets that were used in previous orthodontic treatments were evaluated in this experiment. The surface morphology and the composition of the deposits found in the brackets were evaluated with rugosimetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Friction was analyzed by applying tensile tests simulating sliding mechanics with a 0.019x0.025" steel wire. The static friction levels produced by the following ligation methods were evaluated: loosely attached steel ligature around all four bracket wings, steel ligature attached to only two wings, conventional elastomeric ligation around all 4 bracket wings, and non-conventional Slide® elastomeric ligature. Results: The results demonstrated the presence of biodegradation effects such as corrosion pits, plastic deformation, cracks, and material deposits. The main chemical elements found on these deposits were Carbon and Oxygen. The maximum friction produced by each ligation method changed according to the time of intraoral use. The steel ligature loosely attached to all four bracket wings produced the lowest friction levels in the new brackets. The conventional elastic ligatures generated the highest friction levels. The metallic brackets underwent significant degradation during orthodontic treatment, showing an increase in surface roughness and the deposit of chemical elements on the surface. Conclusion: The levels of static friction decreased with use. The non-conventional elastic ligatures were the best alternative to reduce friction

Mechanical Properties of Mini-Implants Used in Extra-Radicular Anchorage

Objective: To evaluate the mechanical properties of mini-implants (MIs) manufactured from stainless steel and compare them with conventional titanium-aluminum-vanadium alloy MIs. Material and Methods: The following groups were formed: G1 (n=24), 8×1.5 mm steel MIs; G2 (n=24), 12×2.0 mm steel MIs; and G3 (n=24), 10×1.5 mm titanium MIs. The 72 MIs were inserted in the infra zygomatic crest region of the maxilla and retromolar trigone in the jaw of 10 pigs. Pull-out, insertion torque, fracture and percussion tests were performed in order to measure the tensile strength, primary stability and fracture strength of MIs. A digital torque gauge was used to measure insertion and fracture torque, a universal mechanical testing machine was used for pull-out testing and a periotest device was used to measure the micromovement of MIs. For morphological and MI component evaluation, scanning electron microscopy (SEM) was performed. D\u27Agostino & Pearson, Kruskal-Wallis, and Dunn post-hoc and normality tests were used. Results:G2 insertion and fracture torques were significantly higher than G1 and G3 insertion and fracture torques (p<0.05). The pull-out and percussion tests presented similar values among the groups. SEM revealed that the fracture point was predominantly on the fourth thread for steel MIs (G1 and G2) and on the seventh thread for titanium-aluminum-vanadium MIs (G3). Conclusion: The mechanical properties of stainless steel MIs are superior to those of titanium-aluminum-vanadium alloy MIs

Effects of piezocision in orthodontic tooth movement : a systematic review of comparative studies

The aim of this systematic review was to evaluate the effects of piezocision in accelerating orthodontic tooth movement (OTM) and its possible adverse effects. The Databases Medline, Embase, CENTRAL and LILACS were searched until March 2019, for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that used piezocision associated with orthodontic treatment. A manual search was also performed. The search, studies selection, assessment of risk of bias and data collection were carried out by two independent reviewers. Eleven publications were included in this review (4 CCTs and 7 RCTs). No study presented low risk of bias. Different types of tooth movement were evaluated: lower anterior alignment, en-masse retraction, overall orthodontic treatment and canine distalization. A total of 240 participants were analyzed in the included studies. Seven studies found significant acceleration in the piezocision group, while two studies found no differences. Adverse effects regarding patient?s satisfaction, pain perception, or worsening of periodontal parameters were not observed. There was no consensus concerning anchorage loss and root resorption. The literature does not provide high-quality evidence to confirm that Piezocision results in significant OTM acceleration. Therefore, high-quality RCTs should be conducted to allow reliable conclusions about the effects of piezocision in orthodontics

Effectiveness of Chewing Gum Containing CPP-ACP for Remineralisation of Demineralised Enamel around Orthodontic Brackets: An in Situ Study

Objective: To evaluate the effectiveness of chewing gums containing CPP-ACP in remineralisation of demineralised enamel around orthodontic brackets. Material and Methods: Enamel blocks from 120 bovine incisors were used. The blocks were flattened and polished, followed by the development of incipient subsurface caries. The blocks have been subjected to a baseline microhardness analysis. Orthodontic brackets were bonded to the exposed area of the blocks, reserving an area for hardness analysis. An in situ crossover (three-way crossover phases of 21 days with an interval of one week between them), controlled, randomised and blind experimental model was used, with the participation of 12 volunteers divided into groups: G1 – negative control group, without chewing gum; G2 – conventional sugar-free chewing gum, without CPP-ACP (placebo); and G3 – sugar-free chewing gum with CPP-ACP. The following parameters were analysed: superficial linear (Ra), volumetric roughness (Sa), and superficial structural loss, which was indicated by Gap measurement (difference between the healthy and treated area). Statistical tests used were the Friedman, Wilcoxon and Shapiro-Wilk, Kruskal Wallis' nonparametric tests and ANOVA. Results: There was a significant reduction in enamel microhardness after demineralisation in all the groups (p<0.05). This deleterious effect was attenuated in the three groups after the final evaluation, although there were no statistical differences (p<0.05); however, the final values did not return to the baseline values (p<0.05). Conclusion: Chewing gum containing CPP-ACP did not promote in situ remineralisation of demineralised enamel around orthodontic brackets

Effect of Different Enamel Conditioning on the Bond Strength of a Resin Modified Glass Ionomer Cement and Ceramic Brackets

The introduction of direct bonding of brackets was a major development in the quality of care provided to the orthodontic patient. Resin composites have been the standard material for direct bonding in Orthodontics for many years. However, they are sensitive to moisture contamination and do not release fluoride. Caries formation during treatment remains a concern to the orthodontists. An adhesive system that provides sufficient retention to orthodontic accessories and that prevents caries development would be ideal. Recent reports have suggested that resin modified glass ionomer cements may have these properties. The use of ceramic brackets has increased in the past years due to a higher demand for a more esthetic orthodontic appliance. This investigation was designed to evaluate the effect of different enamel conditioning procedures on the shear bond strength and on the bond failure pattern of a resin modified GIC used to bond mechanically retained ceramic brackets. One hundred and five human premolars extracted for orthodontic reasons were randomly assigned to one of the seven treatment groups. The tooth samples were stored in distilled water at room temperature until ready for bonding. After bracket placement the specimens were stored in distilled water at room temperature for 24 hours. The shear force necessary to debond the brackets was recorded using an lnstron Universal Testing Machine at a cross head speed of 0.05 mm/min. The characteristics of bond failure were evaluated under a stereo microscope and Adhesive Remnant Index (ARI) was assigned according to the amount of adhesive remaining on the tooth and the bracket Based on the results of the investigation the following conclusions were drawn: 1. There was a significant difference in the mean shear bond strength values obtained with different enamel treatments. Moisture contamination significantly decreased the: SBS of GIC on those groups that had enamel conditioned with polyacrylic acid. 2. When the manufacturers recommendations for enamel preparation were followed (l0% polyacrylic acid for 20 seconds, rinse, apply wet cotton pellet) the mean bond strength obtained was the lowest and the most variable among the groups tested. 3. Overall enamel etching with 35% phosphoric acid for 15 seconds resulted in higher and more consistent SBS values than those observed in the groups that had tooth surface conditioned with polyacrylic acid. 4. There was a statistically significant difference in the failure sites among the seven different enamel treatment groups. All brackets bonded with composite resin had 100% of the adhesive remaining on the enamel (adhesive failure at the brackets-adhesive interface). The GIC groups showed a more variable pattern with most of the failures of cohesive nature (within the adhesive). 5. All different treatment groups produced SBS values that are considered clinically acceptable. Therefore, resin modified glass ionomer cement may be considered an alternative to composite resin for direct bonding of mechanically retained ceramic brackets. Moisture contamination decreased SBS. but seamed not to preclude the use of GIC as an adhesive material

Corticotomias alveolares na Ortodontia: indicações e efeitos na movimentação dentária

INTRODUÇÃO: a busca pelo aumento na eficiência dos tratamentos ortodônticos é uma constante em diversas áreas da Ortodontia atual. A realização de corticotomias alveolares pouco antes da aplicação de forças ortodônticas vem sendo sugerida como uma forma de potencializar a movimentação dentária e, consequentemente, o tratamento ortodôntico como um todo. OBJETIVO: o presente artigo revê a perspectiva histórica dessa abordagem terapêutica, apresenta e ilustra com casos clínicos suas principais indicações e, por fim, discute os fundamentos biológicos que justificam sua utilização