LAUSR

BACKGROUND AND OBJECTIVE As the main connector of teeth to the surrounding bone, the periodontal ligament (PDL) plays an important role in absorption and distribution of physiological and para-physiological loading. Despite the difference in the mechanical response of the PDL in tension and compression, little information is available on its viscoelastic behavior in compression. To explore the contribution of the fluid phase of the PDL, the aim of the present study was to measure its nonlinear time-dependent behavior in compression. MATERIAL AND METHODS The in vitro dynamic compressive tests were carried out over a wide range of frequencies at three different preloads. Also, a generalized Maxwell model was proposed based on the experimental data to develop a viscoelastic model for subsequent computational analysis of the PDL. RESULTS The higher values of loss factor in compression found in the range of 0.03-0.4 than those of 0.04-0.08 reported in tension, implies the focal role of the fluid phase in compressive dynamic response. Furthermore, the model parameters predicted that with an increase in preload, the role of the viscous components decrease, whereas the role of the elastic component increases. CONCLUSION The viscous effect of the PDL in compression is greater than that in tension. Also, the dependence of the relaxation modulus of the bovine PDL on the applied load indicates its nonlinear viscoelastic behavior in compression.