Effect of intrinsic wetness and regional difference on dentin bond strength

Objectives: The aim of this, investigation was to determine the influence of intrinsic wetness on regional bond strengths of adhesive resins to dentin. Methods: Human caries-free third molars were randomly divided into three groups for-bonding: Group 1 - no pulpal pressure; Group 2 - pulpal pressure of 15 cm H2O; and Group 3 - dentin dried overnight in a desiccator. Clearfil Liner Bond Il (Kuraray) or One Step (Bisco) adhesive resins systems were applied to the flat dentin surfaces and the teeth were, restored with APX resin composite (Kuraray). After 24 h in water at 37 degrees C, the specimens were sectioned into 0.7 mm thick slabs and divided into three regional subgroups according to the remaining dentin thickness and visual criteria: pulp hem, center, and periphery. The slabs were then trimmed for the micro-tensile bond test and subjected to a tensile force and crosshead of 1 mm/min. The data were analyzed with ANOVA and Fisher's PLSD test at a confidence level of 95%. The fracture modes were determined under a scanning electron microscope (JXA-840, JEOL, Japan). Results: No significant regional difference was observed for the Group I and 2 specimens-restored with Clearfil Liner Bond II (p > 0.05), However, bond strengths significantly decreased at the pulp horn region of the Group 1 and 2 specimens restored with One Step (p < 0.01). All bond strengths of Group 3 decreased significantly and regional differences were not evident (p > 0.05), Significance: The dentin adhesive system should be chosen according to the substrate and region to be bonded, since bond strengths can vary according to the intrinsic wetness, region, and the adhesive system. (C) 1999 Published by Elsevier Science Ltd on behalf of the Academy of Dental Materials. All rights reserved.