Degradation of resin-bonded human dentin after 3 years of storage

Purpose: To test, in vitro, the null hypothesis that there was no difference in the ultrastructure of adhesive-bonded, acid-etched dentin aged under accelerated conditions in mineral oil or artificial saliva. Methods: Beams of human dentin bonded with three total-etch adhesives were retrieved from the two storage media after 3 years and prepared for transmission electron microscopy. Results: Hybrid layers from specimens aged in mineral oil exhibited structural integrity of the collagen network. Conversely, abnormal hybrid layers were seen in specimens aged in artificial saliva, with progressive disintegration of the fibrillar network to the extent that it was beyond detection by collagen staining. Self-destruction of collagen matrices can occur in resin-infiltrated dentin, and to a lesser degree, in mineralized dentin in the absence of bacterial or salivary enzymes.