Effect of remaining dentin thickness and primer application technique on microtensile bond strength

Abstract

To evaluate the effect of primer application techniques, type of adhesives and remaining dentin thicknesses on microtensile bond strength (µTBS) of 4 different adhesive systems, 112 Flat occlusal surfaces of sound third molar were randomly allocated into 16 groups based on 2 remaining dentin thicknesses (RDT), 2 application techniques and 3 adhesive systems, e.g., Three step etch-and-rinse (Optibond FL; OFL), Two step self-etch (Clearfil SE Bond; CSE), and Universal adhesive (Single Bond Universal; SB). SB was applied in either etch-and-rinse (ER) or self-etch (SE) mode. Simulated pulpal pressure was performed during bonding procedure and 6-month water storage (37 oC). After resin composite buildup and water storage, stick-shaped specimens from each tooth underwent µTBS testing. Statistical analysis was performed with three-way ANOVA test and Tukey Post Hoc test. The fractured specimens were evaluated for mode of failure using a stereomicroscope. The fracture sufaces of each group were also observed using SEM. The mean µTBS values were significantly affected by RDT, application technique, and types of adhesive. Neither RDT nor primer application technique affected µTBS of SB in ER mode whereas application technique affected both conventional and universal self-etch adhesive. RDT also influenced µTBS of OFL. The RDT and application technique differently affects the µTBS of dentin bonding which is product-related. Etch-and-rinse systems had higher bond strength to superficial dentin than to deep dentin whereas self-etch systems were more sensitive to both RDT and application technique. The universal adhesive should be use following the manufacturer's recommendations when apply on either superficial or deep dentin.