Evaluation of the micro-mechanical strength of resin bonded-dentin interfaces submitted to short-term degradation strategies

Abstract

The aim of this study was to evaluate the microtensile bond strength (μTBS) and confocal micropermeability of resin bonded-dentin specimens created using two representative two-step/self-etch adhesives submitted to short-term period degradation strategies such as simulated pulpal pressure, thermo- or mechanical-cycling challenges. Clearfil SE Bond (CSE) and Silorane adhesive (SIL) were bonded to flat deep dentin from seventy extracted human molars and light-cured for 10 s. Composite build-ups were constructed using with Filtek Z350 XT and Filtek P90 respectively. The specimens of each adhesive group were subjected to three different accelerated aging methods: (1) thermo-cycling challenge (5000 cycles); (2) mechanical-cycling load (200,000 cycles); (3) experiment and (4) conventional method for simulated pulpal pressure (20 cm H₂O). Control resin-bonded specimens were stored in distilled water for 24 h. μTBS and confocal microscopy (CLSM) micropermeability evaluation were performed and the results were analyzed using Two-way ANOVA and Tukey's tests (α=0.05). The CLSM evaluation revealed micro-cracks within the Silorane-bonded dentin subsequent to mechanical-cycling load, whereas, the simulated pulpal pressure induced evident micropermeability in both bonding agents. Mechanical loading provides discernible bonding degradation in a short-term period in resin-bonded dentin created using two-step/self-etch adhesives. However, simulated pulpal pressure may reduce the sealing ability of self-etch adhesives causing greater water uptake within the resin-dentin interface.