Fatigue of the resin–dentin interface: A new approach for evaluating the durability of dentin bonds

There are concerns regarding the longevity of resin composite restorations and the clinical relevance of in vitro bond strength testing to the durability of dentin bonds in vivo.ObjectiveThe objectives of this investigation were to: (1) develop a new method of experimental evaluation for quantifying the durability of dentin bonds, (2) apply this method to characterize the interfacial strength of a selected commercial system under both monotonic and cyclic loading, and (3) distinguish mechanisms contributing to the interface degradation and failure.MethodsA new method for fatigue testing the resin–dentin interface was developed based on a four-point flexure arrangement that includes two identical bonded interfaces. Cyclic loading of specimens comprised of coronal dentin bonded to a commercial resin composite and controls of resin composite was performed to failure within a hydrated environment. Scanning electron microscopy and nanoscopic dynamic mechanical analysis were used to evaluate failure mechanisms.ResultsThe fatigue strength of the resin–dentin interface was significantly lower (p ≤ 0.0001) than that of the resin composite and reported for dentin over the entire finite life regime. Defined at 1 × 107 cycles, the apparent endurance limit of the resin–dentin interface was 13 MPa, in comparison to 48 MPa and 44 MPa for the resin composite and dentin, respectively. The ratio of fully reversed endurance limit to ultimate strength of the interface (0.26) was the lowest of the three materials.SignificanceThe proposed approach for characterizing the fatigue strength of resin–dentin bonds may offer new insights concerning durability of the bonded interface.