Viscoelasticity of Dentin Reduces Vulnerability of Teeth to Fracture

Teeth are exposed to cyclic loads due to their physiological functions such as mastication. With age, such repetitive force causes generation of cracks and caries in dentin, and eventually degeneration due to crack initiation and propagation. The degenerative effects are caused by elevated stress levels in cracked zones and also reduction of structural toughness due to presence of microstructural cracks. Visco-elastic property improves the structural life span by decrease of stress intensity and improved toughness of the material. The reduction of stress intensity results from the energy dissipation. Moreover, elevation of visco-elastic property reinforces toughness of the structure leading to a higher threshold of fracture. Visco-elasticity of dentin is due to water content and fibrous structure of collagenous portion. By aging and many dental restorations such as root canal therapy in which teeth are highly prone to crack initiation and propagation, visco-elasticity of dentin is reduced. Such decrease is due to tissue dehydration and consequent degeneration of fibrous structure with age. It is hypothesized that the threshold of damage in dentin which is prone to physiological cyclic loading, decreases by reduction of visco-elastic property. This hypothesis may be applied in study of dental pathology and contributes to improvement of restorative materials for proper fatigue life.