Fractured surface characterization: wet versus dry bonding

Objective: Fractographic analysis was conducted to evaluate the resin-dentin bond structures made under wet and dry conditions. Methods: Resin-dentin bonded specimens were prepared using two adhesive resin systems (Single Bond/SB; 3M and All Bond 2/AB2; Bisco Inc) under wet and dry conditions. The specimens were sectioned perpendicular to the adhesive interface to produce a square bar-shaped specimen (adhesive area: 0.9 mm(2)) by means of a diamond saw. The mean bond tensile test was then conducted at a crosshead speed of 1.0 mm/min. The mean bond strengths were statistically compared with two-way ANOVA and Fisher's PLSD test (p < 0.05). Subsequently, the fractured surfaces of all specimens were examined using SEM and the area fractions of failure modes (%) were measured using an image analyzer on SEM microphotographs. Results: No significant differences in tensile-bond strength were observed between SB (60.1 +/- 16.4 MPa) and AB2 (69.8 +/- 17.4 MPa) (p > 0.05) under wet conditions. However, the bond strength either of SB or AB2 made under wet conditions was significantly greater than those made under dry conditions (SB: 26.2 +/- 12.5 MPa and AB2: 6.8 +/- 3.3 MPa) (p < 0.05). Under fractographic analysis, the major portion at the fractured surface was occupied by the cohesive failure of bonding resin and the resin composite for the wet conditions, and the top of the hybrid layer for the dry conditions in both systems. Significance: The interaction between the top of the hybrid layer and the bonding resin influenced the bond integrity. (C) 2002 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.