RESUMO
Background: Tooth bleaching is, today, one of the most widespread cosmetic treatments in dental practice, so it is important to determine whether it can interfere with orthodontic bonding or not. Aim: The aim of this study was to assess the in vitro effects of 35% hydrogen peroxide bleaching agent on the shear bond strength of orthodontic brackets. Materials and Methods: Forty-five upper bicuspids were divided into three groups (n = 15). In the control Group (C), the brackets were bonded without previous bleaching treatment. Group 1 (G1) was treated with 35% hydrogen peroxide bleaching agent 24 h before bracket bonding. Group 2 was also bleached, and the brackets were bonded after 30 days. The shear bond strength of the brackets was measured using an EMIC machine, and the results were analyzed by ANOVA. Results: There were no statistically significant differences between the three groups (P > 0.05), with Group C showing a mean bond strength of 9.72 ± 2.63 MPa, G1 of 8.09 ± 2.63 MPa, and G2 of 11.15 ± 4.42 MPa. Conclusion: It was possible to conclude that 35% hydrogen peroxide bleaching agent does not affect the shear strength of orthodontic brackets bonded 24 h and 30 days after bleaching.
RESUMO
OBJECTIVE: This in vitro study was designed to evaluate the shear bond strength (SBS) of orthodontic metal brackets bonded by direct and indirect techniques. METHODS: Thirty healthy human maxillary premolar teeth were used. The teeth were divided into three groups of 10 teeth each: Group I - indirect bonding with SondhiTM Rapid-Set system (3M/Unitek), Group II - indirect bonding with TransbondTM XT adhesive system (3M/Unitek) and Group III - direct bonding with TransbondTM XT adhesive system (3M/Unitek). After bonding and obtaining the specimens for the study, the specimens were subjected to SBS testing in a universal testing machine (Emic, model DL-500). The Kolmogorov-Smirnov test was applied to ascertain that the data had a normal distribution and the Bartlett test to check whether there was homogeneity of variance. One-factor analysis of variance was performed and, subsequently, Tukey's test for paired means. A 5% significance level was adopted. RESULTS: The results of Group I were 67.6 (N) and 5.9 (MPa); Group II, 68.9 (N) and 6.1 (MPa) and Group III (control), 92.5 (N) and 8.1 (MPa). CONCLUSION: It can therefore be concluded that the means for Group III were significantly higher compared with Groups I and II in both Newton (N) and Megapascal (MPa) values. The means attained by the indirect bonding technique used in Groups I and II, however, exhibited no statistically significant differences.
OBJETIVO: objetivou-se com esse trabalho avaliar, em um estudo realizado in vitro, a resistência ao cisalhamento de braquetes metálicos ortodônticos colados pelas técnicas direta e indireta. MÉTODOS: foram utilizados 30 dentes pré-molares superiores humanos hígidos. Os dentes foram divididos em três grupos de 10 dentes: Grupo I - colagem indireta com sistema Sondhi Rapid-Set (3M/Unitek); Grupo II - colagem indireta com sistema Transbond XT (3M/Unitek); e Grupo III - colagem direta com sistema Transbond XT (3M/Unitek). Após realização das colagens e confecção dos corpos de prova, esses foram submetidos ao teste de cisalhamento em uma máquina universal de ensaios da marca comercial EMIC, modelo DL-500. Foram aplicados os testes de Kolmogorov-Smirnov, para verificar se os dados tinham uma distribuição normal, e o teste de Bartlett, para verificar se existia igualdade entre as variâncias. Aplicou-se a análise de variância de um fator e, posteriormente, o teste de Tukey para o contraste pareado de médias. O nível de significância foi de 5%. RESULTADOS: os resultados do Grupo I foram 67,6N e 5,9MPa; do Grupo II foram 68,9N e 6,1MPa; e do Grupo III (controle), 92,5N e 8,1MPa. CONCLUSÃO: pode-se concluir que tanto para os valores em Newtons (N) como para os valores em Megapascal (MPa), a média do Grupo III foi significativamente maior em relação aos Grupos I e II. Já para as médias onde a técnica indireta foi usada (Grupos I e II), não houve diferenças estatisticamente significativas.