Effect of a novel prime-and-rinse approach on short- and long-term dentin bond strength of self-etch adhesives.

This study investigated the effects of the prime-and-rinse approach, using a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primer, on the short- and long-term dentin microtensile bond strengths (MTBSs) of mild self-etch adhesives. Half of sixty human midcoronal dentin surfaces were polished as control (self-etch approach), and the other half were polished and further treated with a 15% MDP-containing primer and thoroughly sprayed with water as prime-and-rinse approach. The dentin surfaces were treated with a self-etch adhesive, and a composite resin was placed on the surfaces. The following materials were used: Clearfil S3 Bond+Clearfil Majesty; G-Bond+Gradia Direct; Adper Easy One+Z250; and i Bond+Charisma. The MTBS was examined after 24 h and 14 months in water storage. The resin-dentin interfaces were analysed using scanning electron microscopy/transmission electron microscopy. Pretreated dentin surfaces were further analysed using scanning electron microscopy and micro-Raman spectroscopy. Compared with the self-etch approach, the prime-and-rinse approach significantly increased the dentin MTBS, regardless of the duration of storage. The scanning electron microscopy/transmission electron microscopy findings revealed that the prime-and-rinse approach removed most of the dentin smear layer. The Raman spectra of the MDP-treated dentin reveal the characteristic spectra of collagen, hydroxyapatite, and the monomer. Therefore, the prime-and-rinse approach using MDP-containing primers prior to the application of mild self-etch adhesives significantly increases the short- and long-term MTBS of dentin.