Fluid flow through dentin–self-etch resin interface during long term in vitro aging

This work aimed at characterizing the interface between dentin and the resin-infiltrated dentin made following the etching procedure that prepares for the bonding of tooth-colored restorations. The non-destructive measurement of fluid flow through the dentin–self-etch resin interface was followed repeatedly during a two year aging period. Two self-etch adhesive systems were selected for experiments on the evolution of permeability and evaluation of infrared spectral changes following the 24 month aging period. The adhesives contained water and a co-solvent, namely acetone for iBond, and t-butanol for Xeno V. For both adhesive systems, the permeability decreased during the first 3 months after etching, reaching values of − 66.9 and − 70.5% for iBond and Xeno V, respectively. Afterwards, the fluid flow slowly increased but still remained below 50% of the initial value following the 2-year aging period. The slow degradation of the resin–dentin interface, attributed to water impregnated collagen hydrolysis, is evidenced by these variations in fluid flow, and is also noted by the increase in water-related infrared absorption bands at 3300 cm− 1 and at 1600 cm− 1. The results are discussed in terms of co-solvent hydrophobicity, evaporation rate and viscosity together with resin infiltration depth and affinity for water.