Characteristics of the aging rat mandible.

The study evaluates the effect of age and sex on the physical characteristics of rat mandible. Wistar derived rats were divided into four groups; young male (4-6 months old), old male (23-25 months old), young female (4-6 months old) and old female (23-25 months old). Mandibles were removed and cleaned of soft tissue, placed on a dental X-ray film and exposed together with an aluminium stepwedge 0.5-3.0 mm. Body weight, and weight, volume, length, base, height, area, density of the mandible were recorded. Also the optical density of the coronoid process, condylar process and mandibular gonion area were measured using a digital densitometer and related to equivalent density of aluminium. Body weight and mandible weight showed age and sex related changes. In most morphometric data there was age but no sex differences. No densitometric differences were found between young or old male or female in the coronoid process, condylar process or gonion. Male rats have greater body weight and mandible weight associated with more food consumption which eventually increased masticatory muscle activity. No missing teeth were noted among male or female aged rats. The results presented here suggest that age-related changes in rat mandible are not general phenomena, but rather specific and limited to some morphometric parameters but not to densitometric parameters. The integrity of the dentition and normal masticatory system activity during aging may be the underlying mechanism.