Characterization of the Elastic and Hyperelastic Modulus of Human Periodontal Ligament

Objectives: The goal of this study was to characterize the elastic modulus (E) and hyperelastic properties of the human PDL and investigate the anatomical variations that may exist in these properties.
Methods: Fresh, frozen PDL in alveolar bone samples were acquired from deceased individuals and sectioned into 5mm (length) x 2mm (width) x 1mm (thickness) samples of PDL linked to alveolar bone and tooth. Twenty-one samples were acquired from 6 separate teeth from 2 individuals. Samples were mounted in a dynamic mechanical analyzer (DMA). The DMA applied stress ramping forces from .001N to 1N over a period of 1 minute and recorded the dimensional change throughout the force application. Stress-strain curve was calculated. The E was calculated and compared between anatomic locations. Hyperelasticity constants were calculated in Ansys using a Mooney Rivlin Model (MRM).
Results: There was no statistical significance between any anatomic locations of PDL from current human samples (p>0.05). Calculated mean (SD) for E were as follows: mesial=17.5(9.5)MPa, distal=23.7(15.7)MPa, coronal=19.5(9.7)MPa , and middle=20.1(15.0)MPa. The E values of human PDL were significantly greater than that of bovine’s 0.79± 0.18. MRM constants calculated from human data also differ from constants calculated from bovine data.
Conclusions: Human PDL displays significantly greater elastic modulus values by nearly 2 orders of magnitude compared to known samples of bovine PDL. This could be attributed to the smaller thickness of human PDL. Further investigation into the microstructure of human PDL should be conducted to analyze anatomic differences that may contribute to this phenomenon. Human PDL also displays different hyperelastic modulus constants and behavior compared to bovine samples.