Hydration and dynamic fatigue of dentin

Abstract

An experimental investigation on the dynamic fatigue response of dentin was conducted to examine the influence of stress rate on the strength and energy to fracture. Rectangular beams were prepared from the coronal dentin of bovine maxiallary molars and subjected to fourpoint flexure to failure. The dentin beams were examined in the fully hydrated and dehydrated condition at stress rates ( ) ranging from 0.01 to 100 MPa/s. Results for the hydrated dentin showed that the flexure strength, energy to fracture, and flexure modulus all increased with increasing stress rate; the flexure strength increased from 100 MPa (( ) ϭ 0.01 MPa/s) to 250 MPa (( ) ϭ 100 MPa/s). In contrast, the elastic modulus and strength of the dehydrated dentin decreased with increasing stress rate; the flexural strength of the dehydrated dentin deceased from 170 MPa (( ) ϭ 0.01 MPa/s) to 100 MPa (( ) ϭ 100 MPa/s). While the hydrated dentin behaved more like a brittle material at low stress rates, the strain to fracture was found to be nearly independent of ( ). According to the experimental results, restorative conditions that cause development of static stresses within the tooth could promote a decrease in the damage tolerance of dentin.

Nanoscopic dynamic mechanical properties of intertubular and peritubular dentin

“…viscous) behavior, the collective trend indicates that increasing quasi-static load magnitude exhausts the capacity for viscous deformation in both constituents. A similar trend was noted in dynamic fatigue of bovine dentin evaluated under hydration [Arola and Zheng, 2006] where quasi-static loading applied at low rates exhausted the time-dependent deformation and its contribution to fracture energy. In that study, it was believed attributed to the organic component of the intertubular dentin.…”

Tubule orientation and the fatigue strength of human dentin

“…According to results of previous studies on the mechanical behavior of dentin, differences in the flexural responses resulting from temperature are expected to be small [34,35]. The fatigue strength of dentin increases with frequency [24] and rate of loading [36]. Therefore, the fatigue strength of dentin resulting from oral activities would be expected to be lower than the estimates presented herein.…”

Degradation in the fatigue strength of dentin by cutting, etching and adhesive bonding

“…The importance of this issue is that the influence of surface flaws resulting from the bur or etching treatments on the fatigue strength of dentin could be different if tested at 2 Hz or lower frequency. Hydrated dentin exhibits increasingly brittle behavior with reduction in loading rate as shown in a previous evaluation on the dynamic fatigue behavior of dentin [57]. That would suggest that testing at 5 Hz frequency could have diminished the degree of reduction in fatigue strength that occurs by flaws introduced by the bur treatments.…”