THE INFLUENCE OF ABSOLUTE-HUMIDITY ON SHEAR BOND ADHESION

Objectives: The purpose of this study was to investigate the relations hip between dentine shear bond strength, using data from experiments p erformed according to a standard protocol, and the absolute humidity f or a new, fourth generation dentine adhesive system. Methods: Results of seven recently performed adhesion experiments using the same protoc ol and product were analysed. Groups of 10 human molars were each bond ed in a humidity chamber. The temperature and relative humidity condit ions varied from 23 to 37 degrees C and 30 to 95%. After bonding of th e composite resin a shear bond test at a crosshead speed of 2.0 mm/min was performed. Results: The bond strength levels of the dentine adhes ive system were influenced significantly by extreme temperature and hu midity differences. Adhesion levels varied from 27.8 (SD 8.5) MPA to 1 2.8 (SD 1.4) MPA. Isobond strength curves are a good method to gain in sight into the humidity sensitivity of adhesive systems. Conclusions: Results of in vitro adhesive bonding procedures for a dentine adhesive can be significantly influenced by the absolute humidity levels at wh ich the procedures are performed. Consequently ''Materials and Methods '' sections of publications should refer to absolute humidity or tempe rature and relative humidity levels as a relevant parameter. Copyright (C) 1996 Elsevier Science Ltd.