Effect Of Bleach On Adhesive Strength Between Enamel And Resin

Objective The physicochemical properties and biological properties of the enamel surface will change after bleaching,which may adversely affect the resin adhesion strength of tooth enamel.This study studied the change of bonding strength of the new filling resin after bleaching,and the influence of bleach on the bonding strength of the old filling resin.In order to explore the effect of bleach on the adhesion properties of enamel,and to provide theoretical basis and clinical reference for the combined application of bleaching and resin filling.Methods This study consists of two parts.Experiment one,thirty fresh bovine incisor teeth were divided into six groups:A1(control group),B1(bleaching control group),C1(sodium ascorate group),D1(tea polyphenols group),E1(remineralization solution group)and F1(ethanol group).In addition to the blank control group,the experimental teeth of the other groups were bleached,and then groups C1 to F1 were treated with 10%sodium ascorbic acid,10%tea polyphenols,remineralization solution,and 75%ethanol,respectively,and immediately filled with enamel resin.The microtensile strength of each group of samples was tested.The bonding interface was observed by scanning electron microscope.Experiment two,fifty fresh bovine incisor teeth were filled with resin and aged.The teeth were divided into five groups:A2(blank control group),B2(bleaching control group),C2(tea polyphenols group),D2(ethanol group),and E2(sodium ascorbic acid group).Except the blank control group,the samples of each group were bleached.The specimens from C2 to E2 groups were treated with 10%tea polyphenols,75%ethanol,and 10%sodium ascorbic acid,respectively,and the shear strength was measured.Data were analyzed using Prism Graphpad software version 9.4 with the Kruskal-Wallis test,and P<0.05 indicates that the difference is statistically significant.Results In experiment one,the micro-tensile strength of the B1 bleaching control group was significantly lower than that of the blank control group(P<0.001).The micro-tensile strength of the sodium ascorbate group,the tea polyphenols group and ethanol group was significantly higher than that of bleached control group(P<0.05).But,there was no significant difference in micro-tensile strength between the sodium ascorbate group,the tea polyphenols group and the blank control group(P>0.05).It was observed by scanning electron microscopy that resin protrusion on adhesive interface was more in blank control group,regular in shape and uniform in arrangement,while in bleached control group,resin protrusion on adhesive interface was short,less in number and sparse in arrangement.In experiment two,there was no significant difference in the shear strength among the blank control group,the bleaching control group,the tea polyphenols group,the ethanol group,and the ascorbic acid sodium group(P>0.05).Conclusion 1.The resin bond strength decreased significantly immediately after tooth bleaching.2.If necessary,the teeth can be treated with 10%sodium ascorbate,10%tea polyphenols or 75%ethanol after tooth bleaching,and then immediately bonded with resin to improve the bonding strength.3.The bond strength of the original resin restoration will not be affected by bleaching treatment.