We tested these hypotheses using a parametric model of a four cusped, maxillary, bunodont molar in conjunction with finite element analysis. Tooth cusp radius of curvature (RoC) has been hypothesized to play an important role in food item breakdown, but has remained largely unstudied due to difficulties in measuring and modeling RoC in multicusped teeth. The analysis indicates what material and geometrical properties are important in optimizing crown performance and longevity. The results confirm that monolithic crowns are able to sustain high bite forces. Dental nanocomposite crowns have comparable fracture resistance to natural enamel. Zirconia crowns showed the highest fracture loads, lithium disilicate intermediate, and dental nanocomposite lowest. Stages of crack propagation within the crown and support substrate were quantified. In conjunction with a fracture mechanics equation for critical splitting load, the data were used to predict load-sustaining capacity for crowns on actual dentin substrates and for loading with a sphere of different size. Extended finite element modeling (XFEM), with provision for step-by-step extension of embedded cracks, was employed to simulate full failure evolution.Įxperimental measurements and XFEM predictions were self-consistent within data scatter. The structures were observed in situ during fracture testing, and critical loads to split the structures were measured. To quantify the splitting resistance of monolithic zirconia, lithium disilicate and nanoparticle-composite dental crowns.įracture experiments were conducted on anatomically-correct monolithic crown structures cemented to standard dental composite dies, by axial loading of a hard sphere placed between the cusps. The cracks leave 'fingerprints' that offer valuable clues to dietary habits, and provide a basis for a priori prediction of bite forces for different animals from measured tooth dimensions.

Extended three-dimensional finite element modeling with provision for growth of embedded cracks is used to validate this relation. A simple power law relation expresses the critical load for full fracture in terms of characteristic tooth dimensions-base radius and enamel thickness-as well as enamel toughness. Fracture is largely stable, with initial slow growth followed by acceleration as the cracks approach completion around an enamel side wall. Contact loading tests are made on extracted human molars with hard and soft indenting plates to determine the evolution of such cracks with increasing load. The cracks simulate those generated in the molar and premolar teeth of humans and animals by natural tooth function.

A study is made of longitudinal 'channel' cracking in tooth enamel from axial compressive loading.

Load aster cracked