Effect of acid etching and adhesive on the micro-tensile bond strength of surface of aged composite resin

Objective:To determine the effect of acid and adhesive on the tensile bond strength between aged and fresh composite resin.Methods:Forty composite resin specimens(3M ESPE Filtek Z350) were prepared in this study.After being stored in distilled water at 37 ℃ for two months,composite surface were roughened with diamond bur and divided into four groups randomly,and there were 10 specimens in each group,as the control group(group A),ten specimens were used as substrate to adhere new Z350 composite,and the adhesive was applied in group B;37% phosphoric acid etching,rinsed and dried in group C;37% phosphoric acid etching,rinsed and dried,and the adhesive was applied in group D.Specimens were then tested for the micro-tensile bond strength(μTBS) in a universal testing machine at a crosshead speed of 1 mm/min until failure.Results:μTBS of group B(only treated with adhesive) was significantly higher than any other group,whereas group C(only treated with acid) was the weakest one,and there was no significant difference between group D and control group.Conclusions:The use of adhesive can significantly improve the bond strength between aged and fresh composite resin.