Saliva contamination effects at different application steps on bond strength of total etch two-step adhesive / Efeitos da contaminação por saliva em diferentes etapas de aplicação do sistema adesivo convencional de dois passos na resistência de união de restaurações adesivas

Introduction: there are clinical situations in the management of cavities favorable to saliva contamination. Human saliva is a complex mixture of oral fluids and it has been showed that the protein content of the saliva is responsible for the decrease in adhesive bond strength when contamination has occurred. Objective: this study aimed to evaluate the effect of saliva contamination during different steps of application of adhesive system on bond strength of total etch two-step adhesive system. Methods: twenty-five extracted human molars were ground flat to expose occlusal dentin. The bonding system and composite resins were applied to the dentin after etching step under five conditions (n=5/group): G1: control group­no contamination; G2: etching/ contamination/dry/adhesive system application; G3: etching/contamination/wash/dry/adhesive system application; G4: etching/adhesive system application/contamination/wash/dry/adhesive system re-application; and G5: etching/adhesive system application/contamination/dry. Microtensile bond strength was tested after specimens were stored in distilled water at 37ºC for 24h. Data (mean values -µTBS) were analyzed by ANOVA one-way and Tukey tests (α=5%), respectively. Results: Groups G2, G3 and G4 revealed bond strength similar to the control (G1). Group G5 showed significantly lower bond strengths than other groups (p<0.001). Conclusion: the total etch two-step adhesive tolerated salivary contamination except when the contamination occurred after application of the bond and it was only removed with an air jet and adhesive system was not reapplied.

Introdução: a saliva humana é uma mistura complexa de fluidos orais e tem sido demonstrado que o conteúdo proteico da saliva é responsável pela diminuição da resistência adesiva quando ocorre contaminação. Objetivo: este estudo objetivou avaliar o efeito da contaminação salivar durante diferentes etapas de aplicação do sistema adesivo sobre a resistência de união. Métodos: vinte e cinco molares humanos extraídos foram cortados para exposição da dentina oclusal. O sistema adesivo convencional e as resinas compostas foram aplicados na dentina após a etapa de condicionamento sob cinco condições (n = 5 / grupo): G1: grupo controle - sem contaminação; G2: condicionamento ácido/contaminação/secagem/adesivo; G3: condicionamento ácido/contaminação/lavagem/secagem/adesivo; G4: condicionamento ácido/aplicação do sistema adesivo/contaminação/lavagem/secagem/reaplicação do sistema adesivo; e G5: condicionamento ácido/aplicação do sistema adesivo/contaminação/secagem. A resistência à microtração foi testada após o armazenamento das amostras em água destilada a 37ºC por 24 horas. Os dados (valores médios -µTBS) foram analisados por ANOVA unidirecional e testes de Tukey (α = 5%), respectivamente. Resultados: Os grupos G2, G3 e G4 revelaram resistência de união semelhante ao controle (G1). O grupo G5 apresentou resistência de união significativamente menor que os demais grupos (p <0,001). Conclusão: o adesivo convencional de dois passos não foi afetado pela contaminação salivar, exceto quando a contaminação ocorreu após a aplicação adesiva e foi removida apenas com jato de ar e o sistema adesivo não foi reaplicado.

Active compounds and derivatives of camellia sinensis responding to erosive attacks on dentin

Abstract This research explored the potential of Camellia sinensis-derived teas and active compounds to be used as treatments to prevent dentin wear. Human root dentin slabs were randomly assigned to 5 groups (n = 10) as follows: distilled water (DW, control), epigallocatechin-3-gallate (EGCG), theaflavin gallate derivatives (TF), commercial green tea (GT), and commercial black tea (BT). The samples were submitted to a pellicle formation and an erosive cycling model (5x/day, demineralization using 0.01 M hydrochloric acid/60 s) followed by remineralization (human stimulated saliva/60 min) for three days. The samples were treated for 5 min using the test group solutions between the erosive cycles. Dentin changes were assessed with profilometry analysis and FT-Raman spectroscopy. The data regarding wear were analyzed by ANOVA followed by Tukey's test (p < 0.05). EGCG, TF derivatives, and both regular teas significantly suppressed erosive dentin loss (38-47%, p < 0.05). No obvious changes in the Raman spectra were detected in the specimens; however, the DW group had a minor relationship of 2880/2940 cm−1. The phenolic contents in both green and black tea and the important catechins appear to have protective effects on dentin loss.

Effect of chlorhexidine on the bond strength of a self-etch adhesive system to sound and demineralized dentin

This study evaluated the effect of a 2% chlorhexidine-based disinfectant (CHX) on the short-term resin-dentin bond strength of a self-etch adhesive system to human dentin with different mineral contents. Dentinal mineralization was tested at 4 levels (sound, and after 2, 4, or 8 days of demineralization-remineralization cycles) and disinfectant at 2 levels [deionized water (DW, negative control) and CHX]. Dentin demineralization induced by pH-cycling was characterized by cross-sectional hardness (CSH). Each dentin surface was divided into halves, one treated with DW and the other with CHX (5 minutes). Each surface was bonded with a self-etch adhesive system and restored. The specimens were sectioned and subjected to microtensile bond testing. CSH and microtensile bond strength (µTBS) data were analyzed by regression analysis and ANOVA-Tukey tests (α = 5%), respectively. The groups treated with CHX resulted in mean µTBS similar to those found for the groups in which the dentin was exposed to DW (p = 0.821). However, mean µTBS were strongly influenced by dentin mineralization (p < 0.05): the bond strength found for sound dentin was lower than that found for dentin cycled for 8 days, which was even lower than the bond strengths for dentin cycled for 2 or 4 days. The results suggest that the degree of dentin demineralization affects the bond strength of self-etching adhesives, but the use of CHX does not modify this effect.