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

Abstract

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±0.3GPa, 3.4±0.2GPa and 0.9±0.3GPa, respectively. Those values for the resin adhesive control were 2.7±0.3GPa, 2.7±0.3GPa and 0.2±0.02GPa, 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.