Analyses of a Cantilever-Beam Based Instrument for Evaluating the Development of Polymerization Stresses

摘要

Polymerization stress (PS) remains one of the most critical properties of polymeric dental materials, yet methods that can accurately quantify PS has been limited in part due to the complexity of polymerization, and in part due to the instrumentation itself. In this study, we performed analytical and finite element analyses on a cantilever-beam based tensometer to evaluate shrinkage stresses during the polymerization of dental restorative composite. Results for these analyses were used to generate 1) guidelines for designing a tensometer that satisfies the necessary accuracy requirements, and 2) a formula for calculating PS and the instrument sensitivity. The PS generated by a commercial dental composite determined using our new tensometer agrees with the predicted trend when the beam length and/or specimen height is varied. An analytical solution is also derived for the vertical deflection of beam, which can be used for any combination of bending and shearing to properly calculate the PS. This work demonstrates the importance of beam dimension and component relative rigidity to the accuracy of PS evaluation. In addition, an easy-to-conduct calibration procedure is provided that is desirable for periodic tensometer recalibration.