Effect of Local Prism Orientation of Enamel Interface at Different Regions on Bond Strength of a Multi-Mode Adhesive System.

Abstract

The purpose of this study was to evaluate the effect of different enamel regions and the direction of enamel sectioning on the microshear bond strength of a multi-mode adhesive used with either an etch-and-rinse adhesive protocol or a self-etch adhesive protocol. A total of 34 recently extracted human upper premolars scheduled for extraction due to orthodontic treatment were selected for this study. The selected premolars were randomly divided according to the testing procedures. Thirty premolars were assigned for preparing 80 specimens for microshear bond strength testing. While 4 premolars were assigned for preparing specimens for ultra-morphological examination of enamel adhesive interface. The microshear bond strength specimens (n=80) were divided into two main groups (n=40) according to the enamel region that was tested (A); cuspal enamel (A1), and mid coronal enamel (A2). Each group was divided into two subgroups (n=20) according to the direction of tooth sectioning (B); axial sectioning (B1), and tangential sectioning (B2).Each subgroup was divided into two classes (n=10) according to the applied adhesive protocol (C); where the multi-mode adhesive was applied with self-etch adhesion protocol (C1) while (C2) the multi-mode adhesive was applied with etch-and-rinse adhesion protocol. Microshear bond strength was assessed by using universal testing machine at a cross head speed of 0.5 mm/min until failure. Resin-enamel interface was assessed under environmental scanning electron microscope.