Dynamic Mechanical Analysis in Situ Mechanical Stability of Teeth

Objectives: Mechanical stability of teeth is important in bearing high impact static occlusion and dynamic mastication. As teeth are supported by viscoelastic periodontal ligament (PDL) and surrounding alveolar bone (AB), their response to loading may be altered by bone disease including osteoporosis. It is well known that postmenopausal osteoporosis arises from estrogen deficiency. Thus, the objective of this study was to investigate whether the estrogen deficiency changes static and dynamic elastic and viscoelastic stability of teeth in situ using dynamic mechanical analysis (DMA).
Methods: Following IACUC approval, 4 groups of 27 Sprague Dawley rats including 10 wild type (9 months old), 11 bilateral ovariectomized (OVX) (4 of 9 months old at 3 months of post-OVX and 7 of 8 months old at 2 months of post-OVX) and 6 sham surgery (8 months old) were obtained. Mandibles were dissected and a hemi-mandible of each rat was mounted on a loading machine and subjected to DMA. A non-destructive compressive static displacement was applied on molars up to 0.02 mm followed by cyclic loading (-5±4N at 0.5 to 3 Hz). Static elastic stiffness (K) and hysteresis (W), and dynamic complex stiffness (K*) and tangent delta (energy dissipation ability) were measured. The values were tested using one way analysis of variance between groups and Pearson’s correlations. Significance was set at 0.05.
Results: All values were not significantly different between groups (p>0.33). A significant negative correlation was found between K and W independent of the groups (p=0.02).
Conclusions: The DMA successfully assessed elastic and viscoelastic behavior of teeth in PDL and AB socket. The current finding showed that estrogen deficiency had not significant effects on the mechanical stability of teeth. Increase in elastic stiffness may compromise less energy dissipation ability to maintain stability of teeth under static loading.