Relationship between Positional Differences of Occlusal Support and Craniofacial Growth in the Rat

Abstract

I investigated whether differences in occlusal support position affect the craniofacial growth pattern in the rat. Two hundred and four 3-week-old male F344/Jcl rats were randomly divided into three groups. Group A (n=72) served as the anterior occlusal support group, where the vertical dimension of occlusion was raised 1mm at the maxillary first molar, group P (n=72) served as the posterior occlusal support group, where the vertical dimension of occlusion was raised at the third molar, and group C served as controls (n=60). Raisting the occlusion was carried out at 5 weeks of age, when eruption of the third molar is complete. Skull morpholgy, and dry weight of the masticatory muscle were observed and analyzed statistically using EXT-T procedures of multiple comparison cross-sectionally at 7, 9, 12, and 15 weeks of age.
      Cephalometric results showed the facial type was hyperdivergent in group P whereas it was hypodivergent in group A. These changes were due to rotational changes in the viscerocranqum (p<0.001) and mandibular ramus (p<0.001). However, dried masticatory muscle weights were not significantly different between groups A and P. These results indicate that the occlusal support position influences the rotational growth pattern of the rat face. This may result from functional pressure on the temporomandibular joint.