The fracture behaviour of human and pig molar cusps

Masticatory efficiency depends upon the ability of the molar cusps to apply concentrated bite forces to food particles and simultaneously to withstand the dental stresses that may cause enamel fracture. This study investigate d how low-crowned molar cusps in omnivorous mammals, specifically humans, H omo sapiens, and pigs, Sus scrofa, resist fracture under compressive load. A uniaxial compressive load was applied to individual molar cusps with a ma terials testing machine. The progressive loading and deformation of the cus ps were recorded for interrupted and continuous tests. In interrupted tests , the appearance of progressive cusp fracture was recorded. Stiffness and f racture stresses were calculated from continuous test results. Pig cusps re sponded to both interrupted and continuous loads with greater deformation; progressive crumbling of the cusp tip resulted in new occlusal contacts on enamel lophs. Conversely, human cusps showed minimal breakage before failur e. Continuous compressive tests demonstrated the greater stiffness of human cusps, as well as the capacity to sustain higher cusp tip stresses. The gr eater stiffness and high fracture resistance of human cusps may be attribut ed to the thickness of enamel. Test results reflected fundamentally differe nt means of crown stress management that correspond with phylogenetic diffe rences in masticatory function. (C) 2000 Elsevier Science Ltd. All rights r eserved.