STRAIN IN THE FACIAL BONES

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The research proposed here will contribute to a functional understanding of the morphology of the primate facial region. Because the primate face is dominated by the masticatory apparatus, this research will analyze how masticatory forces are dissipated throughout the primate face. This will be accomplished by an analysis of in vivo strain along the facial bones of Macaca fascicularis using strain gages. Rosette strain gages (three strain gage elements with a known orientation to one another) will be bonded directly to facial bones with a cyanoacrylate adhesive. The restrained macaque will then bite a transducer (or chew various types of foods), and bone strain will be recorded on an FM tape recorder and a chart recorder. In order to correlate precisely the animal's behavior with the bone strain signals, the animal and the chart recorder will be videotaped. With a special effects generator, a split-screen display of both animal and recorder will be produced and recorded. After the recording procedure, the raw strains will be played out from the tape recorder into the chart recorder. The maximum and minimum principal strains will then be determined from these raw strain values. Moreover, the direction of the principal strains will be determined. After surface strains have been characterized along different regions of the face of Macaca fascicularis (e.g. the mandibular symphysis, postorbital bar, anterior root of the zygoma, zygomatic arch, supraorbital region and interorbital region), patterns of internal stress will be inferred from patterns of strain. This will be done in order to understand how macaque facial bones dissipate masticatory stress. These data should provide information for understanding the functional significance of facial bone morphology.