A characterization of the mechanical behavior of resin-infiltrated dentin using nanoscopic Dynamic Mechanical Analysis

This study explored the spatial variations in mechanical behavior of resin-infiltrated dentin using nanoscopic Dynamic Mechanical Analysis (DMA). Objective The objectives were to: (1) evaluate the mechanical behavior of resin-infiltrated dentin using a scanning-based approach to nanoindentation, (2) identify contributions of the collagen matrix to time-dependent deformation of the hybrid layer, and (3) assess the importance of specimen hydration on the nanoDMA response. Methods Specimens of completely demineralized dentin infiltrated with commercial resin adhesive and control samples of resin adhesive were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform DMA and to estimate the complex (E*), storage (E′) and loss (E″) moduli over selected regions of evaluation. The importance of hydration on the mechanical behavior was also examined from a comparison of responses in the hydrated and dehydrated conditions. Results In the hydrated state the apparent complex, storage and loss moduli for the resin-infiltrated dentin samples were 3.5 ± 0.3 GPa, 3.4 ± 0.2 GPa and 0.9 ± 0.3 GPa, respectively. Those values for the resin adhesive control were 2.7 ± 0.3 GPa, 2.7 ± 0.3 GPa and 0.2 ± 0.02 GPa, respectively. Viscoelastic deformation of the resin-infiltrated collagen exceeded that occurring in regions of uniform resin adhesive. Though dehydration resulted in a significant increase in both the complex and storage moduli of the macro hybrid layer, the largest changes occurred to the resin adhesive. Significance The microstructure and hydration play critical roles on the mechanical behavior of the hybrid layer and nanoDMA provides a potent measurement tool for identifying the spatial variations.