In vivo measurement of the elastic modulus of the human periodontal ligament

The present study was designated to determine the elastic properties of the periodontal ligament (PDL) in human subjects. A maxillary central incisor was experimentally translated so that stress or strain could be uniformly distributed in the PDL by applying a single force passing through the center of resistance. Displacements were measured under different magnitudes of load using a magnet-magnetic sensing system. From the load–displacement relations, Youngʹs modulus of the PDL was calculated. The values determined were approximately 0.12 MPa under load ranging from 0 to 0.5 N, 0.25 MPa within the range of 0.5–1.0 N, 0.44 MPa under load 1.0–1.5 N, and between 0.69 and 0.96 MPa with 1.5–2.0 N. The values of Youngʹs moduli increased almost exponentially with the increment of load due to a non-linear elasticity of the PDL.