Experimental and theoretical fracture analyses for three biomaterials with dental applications

Dental materials are known as efficient tools to revive the functionality and integrity of decayed/missing tooth structure. Being frequently subjected to different mixtures of tensile and shear loads accompanied by temperature changes and suffering from pre-existing voids and imperfect interfaces at the same time, dental restorations and prostheses are found to be susceptible to crack initiation and growth. In this paper, fracture properties of three dental biomaterials namely polymethylmethacrylate (PMMA), 75Sr and 75Sr10 undergoing mixed tensile-shear loads are investigated. The PMMA used in this study has application as a cold-cured acrylic resin for repairing dental prostheses, while 75Sr and 75Sr10 are dental restorative materials. Fracture growth angle and onset of crack propagation are evaluated experimentally using shortened semi-circular bend specimens made from PMMA. In addition, the generalized maximum tangential strain (GMTSN) criterion is applied to theoretically predict the fracture behavior of the tested PMMA, as well as two other dental bio-composites reported in the literature viz 75Sr and 75Sr10. Good agreement is met between theory and practice when comparing fracture curves extracted from the GMTSN criterion and the experimental data points. Further, it is found that conventional stress- and strain-based fracture models fail to provide suitable estimates of crack growth behavior.