Resistência de união ao esmalte com aplicação do adesivo na base do braquete / Shear bond strength to enamel after application of adhesive on the mesh of brackets

O objetivo deste estudo foi verificar o efeito da aplicação do adesivo na base do braquete, na resistência de união ao cisalhamento ao esmalte bovino. Um total de 160 incisivos bovinos foi condicionado com ácido fosfórico a 37% durante 30 segundos, e o adesivo Transbond XT Primer foi aplicado na base de retenção de 80 braquetes Edgewise para incisivo central superior, enquanto que nos demais braquetes as resinas compostas Transbond XT, Natural Ortho, Tetric Ceram e Z100 foram aplicadas diretamente na base de retenção. As amostras foram armazenadas em água a 37°C durante 24 horas e submetidas ao ensaio de resistência de união ao cisalhamento (RUC) em uma máquina de ensaio universal Instron 4411, com velocidade de 1,0 mm/min. Em seguida, foi avaliado o índice de remanescente adesivo (IRA). Os dados de RUC foram submetidos à Anova 2 fatores e teste de Tukey (α=0,05). A aplicação do Transbond XT Primer na base dos braquetes aumentou significativamente a RUC das resinas Transbond XT, Natural Ortho e Z100, mas diminuiu significativamente a RUC da Tetric Ceram. A maior RUC foi apresentada pela resina Transbond XT. Sem adesivo, a Tetric Ceram demonstrou RUC significativamente maior do que a Z100 e a Natural Ortho. Com adesivo na base do braquete, ocorreu o inverso. A adição do adesivo nos braquetes aumentou as falhas adesivas. Concluiu-se que a aplicação do adesivo na base dos braquetes é indicada para melhorar a união entre a resina e os braquetes...

The aim of this study was to investigate the effect of application of adhesive in the mesh of brackets on bond strength to enamel. One hundred and sixty bovine incisors were acid etched with 37% phosphoric acid for 30s. The adhesive system Transbond XT Primer was applied to the etched enamel and photo activated by LED Ultralume 5 for 10s. Resin composites Transbond XT, Natural Ortho, Tetric Ceram and Z100 were used to bond brackets to enamel. In the half of the sample adhesive Transbond XT Primer was applied to the mesh of brackets before bonding. Shear bond strength was evaluated after 24 h in a universal testing machine Instron 4411 at 1.0 mm/min crosshead speed. The adhesive remnant index (ARI) was evaluated after shear bond strength test. Data were submitted to two-way Anova and Tukey’s test (α=0.05). The use of adhesive in the mesh of brackets significantly increased the bond strength of Transbond XT, Natural Ortho and Z100; however, Transbond XT Primer applied in the mesh of bracket significantly decreased the bond strength of Tetric Ceram. Transbond XT showed significantly the highest shear bond strength. Transbond XT Primer increased the adhesive failures. It can be concluded that the use of adhesive in the mesh of brackets is a good alternative to improve the bond strength of resin to bracket...

Degradação e corrosão de bráquetes metálicos / Degradation and corrosion of metal brackets

Este estudo in vitro teve como objetivo analisar, por meio de microscopia ótica, as alterações superficiais de bráquetes metálicos submetidos ao processo de degradação química. Para este estudo foram utilizadas amostras de três diferentes bráquetes metálicos, separados de acordo com a marca (Morelli®, Aditek® e Abzil®) e soluções de imersão (solução salina 0,05%, saliva artificial, Coca-Cola®, suco de tomate e vinho). A superfície dos bráquetes foi avaliada inicialmente através do microscópico ótico e fotografada para avaliação qualitativa. Em seguida, os bráquetes foram imersos nas soluções por 15, 30 e 60 dias e as alterações decorrentes da exposição das amostras às soluções foram analisadas por meio do microscópico ótico em cada período (15, 30 e 60 dias). Os resultados mostraram que o vinho, Coca-Cola, suco de tomate e saliva artificial não causaram alterações na superficial dos bráquetes. Entretanto, a imersão em solução salina causou corrosão na superfície de todas as marcas avaliadas. Concluiu-se que a solução salina foi a única solução capaz de causar danos à superfície dos bráquetes metálicos, não havendo distinção entre as marcas comerciais dos bráquetes.

This in vitro study aimed to analyze, by means of optical microscopy, surface changes on metallic brackets subjected to chemical degradation process. For this study we have used samples from three different metallic brackets separated according to their brand (Morelli, Aditek e Abzil), and dip solutions (saline solution 0.05%, artificial saliva, Coca-Cola, tomato juice and wine). The surface of the brackets was initially evaluated by optical microscope and photographed for qualitative evaluation. Then, the brackets were immersed in the solutions for 15, 30 and 60 days. The changes resulting from exposure to the solutions were analyzed by optical microscope in each period (15, 30 and 60 days). The results showed that wine, Coca-Cola, tomato juice and artificial saliva did not cause changes in the surface of the brackets. However, immersion in saline solution caused corrosion on the surface of all brands studied. It was concluded that the saline solution was the only solution capable of damaging the surface of metal brackets, with no distinction among the tested brands.

Effect of elastomeric ligatures on frictional forces between the archwire and orthodontic bracket

Aim: To evaluate the frictional force between the archwire and orthodontic bracket generated by elastomeric ligatures with polymer coating (Super slick, TP Orthodontics) and conventional ligatures (Morelli) using two types of insertion techniques. Methods: Forty elastomeric ligatures, 20 with polymer coating and 20 conventional, were evaluated. Each type of ligature was separated into two groups (n=10), according to the insertion mode: conventional or crossed (from mesial to distal region crossed in front). To analyze friction, 40 5-cm-long segments of stainless steel orthodontic archwire 0.019" x 0.025" (Morelli) and Edgewise brackets (slot 0.022" x 0.028"; Morelli) were used. Each set (bracket, wire and elastic) was submitted to frictional testing in a universal test machine (Instron 4411) at a crosshead speed of 5 mm/min. Each bracket was moved 5 mm on the wire, with maximum friction and mean friction being recorded by software. Three readouts were taken for each bracket. Data were submitted to two-way ANOVA and Tukey’s test (p<0.05). Results: It was shown that for maximum and mean friction, the polymer-coated ligature did not differ statistically from the conventional type in a dry environment condition. Ligatures placed incrossed mode promoted significantly greater friction than those placed in conventional mode, irrespective of the type of elastomeric ligature. Conclusions: Friction depended on the insertion mode, but not on the type of elastomeric ligature.

Fracture strength of ceramic brackets submitted to archwire torsional strain

Aim: To evaluate the fracture strength of ceramic brackets submitted to archwire torsional strain. Methods: Different types of maxillary central incisor ceramic brackets from four different commercial brands, Roth prescription (0.022" x 0.028"), were evaluated, namely: Mystique (GAC), InVu (TP Orthodontics), Clarity (3M Unitek) and Luxi II (RMO Ortohodontics). To evaluate the fracture strength, 0.019"x 0.025" stainless steel orthodontic wires were inserted into the bracket channels and submitted to torsion until they fractured. Results: The InVu brackets showed a significantly higher fracture strength than the other brackets (p<0.05), which did not differ significantly among them (p>0.05). Conclusions: Among the brackets tested, the traditional ceramic bracket InVu showed the highest fracture strength, while the Luxi II bracket, obtained the lowest value.