RAFFERTY, K.L.; HERRING, S.W.*; Univ. of Washington; Univ. of Washington: In Vivo Biomechanics of the Snout

The snout is a large diameter, thin-walled tubular structure that receives loads from the teeth. It can be conceptualized both as a rigid object and as an assemblage of several bones that interface at sutures. To gain a better understanding of the biomechanical behavior of the snout, we measured in vivo strains in the premaxillary, maxillary and nasal bones and sutures of miniature pigs, Sus scrofa (n=14, 4-5 months old). Recordings were made during normal mastication (except for the intermaxillary suture) and during stimulations of jaw muscles. As in other parts of the skull, sutural strains were an order of magnitude larger than bone strains, emphasizing the composite nature of the snout. Transverse tension in the intermaxillary suture and transverse compression in the internasal suture suggested that the bilateral occlusion of the molars in pigs tends to collapse the snout. The premaxillary-maxillary suture was strongly tensed. However, evidence for rigid structural behavior was also found. Maxillary strain was tensile, with the axis of tension oriented anterosuperiorly, consistent with a short beam model under shear deformation from the molar loading. Long-beam dorsal bending of the snout was minimal, and torsion was seen only in the premaxillary bones when the incisors made asymmetrical contact. These patterns are also attributable to the strong influence of bilateral molar occlusion. In conclusion, strains in the pig snout reflect its composite nature but also show elements of rigid behavior. Molar occlusion was the most important determinant of strain pattern. Supported by PHS award DE08513.