Role of water on the mechanical characteristics of structural dentine

Abstract

The nature and association of water with dentine matrix and the role that free water plays on the mechanical properties of dentine is not clear. This understanding will offer an insight into role of hydration on the mechanical integrity of dentine and the causes of fracture predilection in endodontically treated teeth. Following experiments were conducted. Gravimetric analysis was done to study the nature and distribution of free water loss from dentine. Fourier Transform Infrared spectroscopy was done to verify any compositional changes occurring in dehydrated and desiccated dentine specimens. Nuclear Magnetic Resonance Spectroscopy to quantify the amount of water that remains in dentine after subjecting to dehydration and desiccation processes. Moir?? Interferometry was used to determine the strain response in dentine during dehydration (21A?C and 60% relative humidity) and rehydration (21A?C and 100% humidity). Three-point bend test and compression test were done to determine the work of fracture in fully hydrated dentine specimens and specimens subjected to dehydration for 72 hours. These experiments highlighted that the free water on the dentine surface, porosities and tubules is lost rapidly and constitutes the major water lost when dehydrated at 21A?C. Moir?? Interferometry showed that the water loss in the first 1-4 hours of dehydration does not bring about any increase in strains in the dentine matrix. However, subsequent loss of free water from the dentine matrix produced a rapid increase in strains. Rehydration produced a complete reversal of dehydration induced water loss and most of strains in dentine. The results of the mechanical tests showed that hydrated dentine had a significantly higher work of fracture than dehydrated dentine specimens.