SEM Observation of Bonding Interface of One-step Adhesive Systems to Root Dentin

Objective: The purpose of this study was to investigate the bonding interface of one-step self-etching adhesive systems to sound or caries-affected root dentin by morphological observation with scanning electron microscopy (SEM). Methods: Freshly-extracted human teeth were used. The cavities were prepared on sound root dentin or by removing root caries, and composite filling was performed using Adper Prompt (3M ESPE, AD), Reactmer Bond (Shofu, RE) or One-Up Bond F (Tokuyama, ON). Two-step self-etching system Clearfil SE Bond (Kuraray) served as controls. One half of the teeth in each group was sectioned longitudinally through the center of the restoration immediately after composite placement. The sectioned surface was fixed in half-Karnovsky's solution, polished and observed under SEM. The interfacial morphology of the other half of the specimens was examined after being stored in water at 37ûC for 1 day. Results: Similar to the control adhesive, gap-free adhesion with structural continuity to sound or caries-affected root dentin was observed for the specimens of AD irrespective of storage time. For RE and ON, although one-dayÐstorage specimens showed perfect adhesion, bonding was broken in some specimens when examined immediately after restoration probably due to the sample preparation procedure. Conclusion: The results indicate that AD is able to produce stable adhesion while the systems which involve glass-ionomer reaction in bonding process form fragile interface at an early stage. This work was supported in part by a Grant-in-Aid for Scientific Research (13470402) from the Japan Society for the Promotion of Science.