Hybridization quality in cervical cementum and superficial dentin using current adhesives

Abstract

Objectives The aim of this research was to determine the hybridization quality of adhesives to gingival cementum and close superficial dentin using both total-etch and self-etch, one-step and two-step adhesives in vitro. Methods Five adhesive systems were used and evaluated in this study; three kinds of two-step adhesives (total-etch—Single Bond and self-etch—Clearfil SE Bond and Clearfil Protect Bond) and two one-step adhesives (Clearfil S 3 Bond, G Bond). Fifteen extracted intact human third molars were used in this study. A diagonal cut which was approximately 45° to the long axis of the roots, with the initiating point located 2 mm below the buccal enamel–cementum junction and ascending towards the pulp chamber was prepared on each tooth. Flat cervical cementum and dentin surfaces were ground with wet 600-grit silicon carbide paper, and bonded with one of the adhesives and finished by applying a flowable resin composite. After 24 h storage at 37 °C in water, the bonded assemblies were sectioned into approximately 1 mm thick slabs. Two central slabs from each tooth were chosen. One slab was totally demineralized in 0.5 M EDTA and the other was not demineralized and immersed into 50% (w/v) solution of ammoniacal silver nitrate for 24 h, and successively exposed to photodeveloping solution for 8 h. The specimens were then processed for TEM observation. Both the stained demineralized silver unchallenged and unstained non-demineralized silver challenged resin–cervical cementum/proximal superficial dentin interface were observed and evaluated under a transmission electron microscope. Results The nanoleakage pathway and extent vary among the different adhesives used and also between the resin–cementum interface and resin–dentin interface. Two-step self-etch adhesives showed better hybridization quality both in cementum and proximal superficial dentin as compared to those of two-step total-etch adhesive and one-step self-etch adhesives. Significance Two-step self-etch adhesives may provide a better sealing in cervical cementum and the proximal superficial dentin region.