Short-term stress relaxation of porcine periodontal ligament - Finding an appropriate visco-elastic model

Findings are presented here from a prototype palpation device for making load-displacement measurements, intended ultimately for in vivo use on humans. Here, the device is applied in vitro to a number of pig-jaws to assess its ability to distinguish visco-elastic properties of the PDL. Four jaws were tested, each test consisting of the application of a series of step displacements to the second mandibular premolar, and allowing the stress to relax over a period of up to 35 seconds. The resulting stress relaxation curves are fit to a number of simple visco-elastic models to assess the most appropriate method of assessing short- and medium-term visco-elastic properties. The results indicate that four-parameter models give significantly better results than three-parameter models and that the time of testing is critical in determining longer time-constant effects. © 2009 Springer-Verlag.