Effect of different application times of 1.3% green tea extract on bond stability of etch-and-rinse adhesive to dentin.

Abstract

The aim of the present study is to evaluate the effect of different times of 1.3% green tea extract (GTE) application on bond stability of and etch-and-rinse adhesive system to dentin. Thirty third molars will have the occlusal enamel removed to expose the superficial dentin. Fragments of dentin will be polished with water-proof abrasive papers (#400 and #600) and will be randomly divided into three groups according to the time of dentin pre-treatment with 1.3% aqueous GTE solution: 0 seconds (control group, without treatment); 30 seconds; 60 seconds. The etch-and-rinse adhesive system will be applied on dentin according to manufacturer's instructions. After that, four cylinders (0.8mm diameter) will be constructed per sample. Photoactivation will be performed with a LED device (Valo, Ultradent 1000 mW/cm2) for 40 seconds. After 24 hours, half of resin cylinders will be submitted to the microshear bond strength testing in a universal machine (0.5mm/min). The other half will be stored for 6 months in a solution that simulates the body fluid (BFS). Failure mode will be analyzed in a stereoscope (40 x). The results of microshear bond strength (MPa) will be analyzed according to its distribution. In case of normal and homogeneous distribution, data will be submitted to two-way ANOVA for repeated measures; otherwise, non-parametric analysis will be conducted. The failure mode distribution will be evaluated by the Qui-squared test. It will be adopted a level of significance of 5%.