Meeting Abstract

P1.143  Monday, Jan. 4  Impact of chronic mandibular loading on craniomandibular size and shape in the laboratory rat GERSTNER, GE*; CARDINAL, MD; ZELDITCH, ML; University of Michigan; University of Michigan; University of Michigan geger@umich.edu

In an effort to gain insight into the relationship between chewing rate and jaw mass, we previously performed surgically-controlled implant studies that increased jaw mass in laboratory rats. Mean licking rates were quantified weekly, and results demonstrated no significant differences in licking rate between the two animal groups, despite a near-doubling of jaw mass in test animals compared with controls. We next assessed how the effects of increased jaw mass affected craniomandibular morphology in these two animal groups and found few significant differences between the groups. However, these previous morphometric studies were not designed to isolate size- versus shape-specific variation. In the present study, we use geometric morphometrics to determine whether doubling of jaw mass affects size and/or shape of crania and mandibles from adult male laboratory rats, 11 of which had 2-g gold implants affixed to the anterior inferior region of the mandibles versus 11 age- and gender-matched surgical controls that had 0.2-g acrylic implants affixed to the same position of the mandibles. After 12 weeks, the animals were sacrificed, and the crania and mandibles dissected, cleaned, photographed and digitized. Preliminary results indicate no significant differences in mandibular shape but the mandibles of the gold-implant group appeared to be ~ 6% larger in overall mandibular size compared with the acrylic group. These results suggest that compensatory neuromotor and musculoskeletal changes associated with this model of chronic loading are surprisingly integrated and/or broadly dispersed. This may explain why the previously observed effects of chronic doubling of mandibular mass were relatively subtle.