Bond strength of self-etch adhesives to bur-cut dentin

Abstract

Objective: This study examined the effects of cutting dentin withdifferent burs at various speeds on microtensile bond strength(lTBS) of two self-etch adhesive systems.Methods: Flat deep dentin surfaces from fifty extracted humanthird molars were divided into five groups according to bur typeand speed of rotation (I) high-speed diamond bur, (II) low-speeddiamond bur, (III) high-speed tungsten carbide bur, (IV) low-speed tungsten carbide bur. Controls were abraded with #600grit SiC paper. A two-step self-etch adhesive, Clearfil SE Bond(SE; Kuraray) and a one-step self-etch adhesive, Clearfil S3Bond (S3; Kuraray) were applied to dentin surfaces and light-cured. Composite build-ups were performed using Filtek Z250(3M ESPE). For lTBS evaluation, composite-dentin beams of0.8 mm2were stressed to failure at a crosshead speed of1 mm/min. The lTBS data was analyzed using two-wayANOVA and Tukey’s multiple comparison tests. Representativefractured beams from each group were prepared for fracto-graphic analysis under SEM.Results: Two-way ANOVA showed that the effects of dentin surfacepreparation, adhesives systems and their interaction were statisti-cally significant (P<0.05). The lTBS were significantly loweredwhen bonding SE or S3 to dentin cut with a high-speed diamond bur(P < 0.05), which produced a thick smear layer and irregularsurface for bonding. SEM observation of the fractured surfacesrevealed mixed and adhesive failures for SE groups; while in S3groups adhesive failures with numerous inclusion droplets predo-minated.