RESUMO
Introduction and Objective : To evaluate the shear bond strength of brackets fixed with different materials (two light-cured nanofilled low-viscosity resins - Transbond Supreme LV and Flow Tain LV and two light-cured traditional resins - Transbond XT and Transbond Plus Color Change) after 10 min and 24 h, and to evaluate the type of failure. Material and methods : Eighty bovine incisors were selected and randomly divided into groups (n = 10) according to the material and fixation period. The brackets were bonded following the manufacturer's instructions and stored in deionized water at 37oC for 10 min or 24 h. After, the specimens were submitted to shear bond strength test at 0.5 mm/min and evaluated for adhesive remnant index (ARI). The data were submitted to Kruskal Wallis and Wilcoxon tests (p < 0.05) and the ARI scores to Chi-Square test. Results: There was a significant difference among the materials (p < 0.05) (after 10 min - Transbond XT > Transbond Plus Color Change > Transbond Supreme LV = Flow Tain LV and after 24 h - Transbond XT > Transbond Plus Color Change = Transbond Supreme LV = Flow Tain LV). There was no significant difference in resistance values between 10 min and 24 h, except for Transbond Plus Color Change. Most groups showed adhesive remaining adhered to the enamel (scores 2 and 3) without statistical significant difference (p > 0.05). Conclusion: The light-cured traditional resins showed higher resistance than the nanofilled materials. The period of fixation had no influence on the resistance for different materials, except for Transbond Plus Color Change.
RESUMO
The aim of this study was to evaluate the shear bond strength of rebonded ceramic brackets after subjecting the bracket base to different treatments. Seventy-five premolars were selected and randomly distributed into five groups (n=15), according to the type of the bracket surface treatment: I, no treatment, first bonding (control); II, sandblasting with aluminum oxide; III, sandblasting + silane; IV, silica coating + silane; and V, silicatization performed in a laboratory (Rocatec system). The brackets were fixed on an enamel surface with Transbond XT resin without acid etching. The brackets were then removed and their bases were subjected to different treatments. Thereafter, the brackets were fixed again to the enamel surface and the specimens were subjected to shear bond strength (SBS) test. The adhesive remnant index (ARI) was then evaluated for each specimen. Data were subjected to ANOVA and Tukey's tests (α=0.05). A statistically significant difference was observed only between Rocatec and the other groups; the Rocatec group showed the lowest SBS values. The highest SBS values were observed for group 1, without any significant difference from the values for groups II, III and IV. Most groups had a higher percentage of failures at the enamel-resin interface (score 1). It was concluded that the surface treatments of rebonded ceramic brackets were effective, with SBS values similar to that of the control group, except Rocatec group.
O objetivo do estudo foi avaliar o efeito de tratamentos da base de bráquetes cerâmicos monocristalinos na resistência de união ao esmalte após recolagem. Setenta e cinco pré-molares foram selecionados e aleatoriamente distribuídos em 5 grupos (n=15) de acordo com o tratamento da base do bráquete: I - sem tratamento, primeira colagem (controle), II - jateamento com óxido de alumínio, III - jateamento seguido da aplicação de silano, IV - jateamento com partículas de dióxido de sílica (silicatização) seguido de silano, V - silicatização realizada em laboratório (Sistema Rocatec). Os bráquetes foram colados no esmalte com Transbond XT sem condicionamento ácido. Em seguida, os bráquetes foram removidos e suas bases foram submetidas aos diferentes tratamentos. Os bráquetes foram recolados, armazenados por 24 h e submetidos ao ensaio mecânico de cisalhamento com velocidade de 0,5 mm/min. Após, o índice de remanescente adesivo (IRA) foi avaliado em cada espécime. Os dados foram submetidos à análise de variância e teste de Tukey (α=0,05). Pode-se observar que houve diferença significativa apenas entre o sistema Rocatec e os demais grupos, o qual apresentou os menores valores de resistência. Os maiores valores de resistência foram observados para o grupo I (controle), sem diferença significativa dos grupos II, III e IV. A maioria dos grupos apresentou maior porcentagem de falhas na interface esmalte/resina (escore 1). Pode-se concluir que os tratamentos da base do bráquete cerâmico foram efetivos, apresentando valores similares ao grupo controle, exceto para o grupo em que foi usado Rocatec.