EFFECT OF PULPAL PRESSURE ON MICROTENSILE BOND STRENGTH OF SELF-ETCH SYSTEMS TO DENTIN. APPLICATION OF TWO ADHESIVE LAYERS

The first objective of this study was to examine effect of simulated hydrostatic pulpal pressure (PP) on μTBS of Bond Force (BF) (Tokuyama Corp., Tokyo, Japan), applied in a single or double layer. The second objective was to evaluate dentin location influence (superficial and deep) on μTBS.Flat coronal dentin surfaces of extracted human molars were prepared. Two groups were created with two different conditions of PP. In group A no PP was present (0 cm) during BF application and composite build-up. In group B a PP (20 cm H2O) was present during BF application. Specimens bonded under PP were stored in water at 37C° under 20 cm H2O for 20 min. For both groups BF was applied in single (subgroups A1,B1) or double layer (A2,B2). Flowable resin composite (Estelite Flow Quick Tokuyama Corp., Tokyo, Japan) was used for the build-up. Beams with a 1.0 mm2 area were obtained and stressed to failure using microtensile tester.Application of two layers of BF showed higher μTBS than single application in all tested conditions. PP was responsible for a statistical reduction in μTBS only when Bond Force was applied in single coat. Superficial dentin showed higher values than deep dentin in all conditions but no statistical differences were found. A highly significant correlation was observed between droplets presence and μTBS results.The application of a double layer of BF is a clinical requirement to avoid the reduction in μTBS and prevent any interference of pulpal pressure.