Correlation between degree of conversion, resin-dentin bond strength and nanoleakage of simplified etch-and-rinse adhesives

Objectives. The aim of this study was to correlate the degree of conversion measured inside the hybrid layer (DC) with the microtensile resin-dentin bond strength (mu TBS) and silver nitrate uptake or nanoleakage (SNU) for five simplified etch-and-rinse adhesive systems. Methods. Fifty-five caries free extracted molars were used in this study. Thirty teeth were used for mu TBS/SNU [n = 6] and 25 teeth for DC [n = 5]. The dentin surfaces were bonded with the following adhesives: Adper Single Bond 2 (SB), Ambar (AB), XP Bond (XP), Tetric N-Bond (TE) and Stae (ST) followed by composite resin build-ups. For mu TBS and SNU test, bonded teeth were sectioned in order to obtain stick-shaped specimens (0.8 mm(2)), which were tested under tensile stress (0.5 mm/min). Three bonded sticks, from each tooth, were not tested in tensile stress and they were immersed in 50% silver nitrate, photo-developed and analyzed by scanning electron microscopy. Longitudinal 1-mm thick sections were prepared for the teeth assigned for DC measurement and evaluated by micro-Raman spectroscopy. Results. ST showed lowest DC, mu TBS, and higher SNU (p < 0.05). All other adhesives showed similar DC, mu TBS, and SNU (p > 0.05), except for TE which showed an intermediate SNU level. The DC was positively correlated with mu TBS and negatively correlated with SNU (p < 0.05). SNU was also negatively correlated with mu TBS (p < 0.05). Significance. The measurement of DC inside the hybrid layer can provide some information about bonding performance of adhesive systems since this property showed a good correlation with resin-dentin bond strength and SNU values. (C) 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.