[Histomorphometric study on age-, diet- and teeth loss-related changes in rat condyle].

To elucidate the mandibular morphological changes due to occlusal and masticatory alterations in addition to aging, 66 Donryu male rats (30-74 weeks old) were divided into three groups, the control group (solid diet), the soft diet group (powder diet containing the same components as the solid one from the 43rd week) and the molarless group (all molars were removed at 43 weeks and then fed a powder diet). The powder diet group and the molarless group were compared with the control group by using a handy microscope system with a CCD camera, soft X-ray pictures and light microscopy. The results obtained are as follows: 1. The height of the mandibular ramus, the length and the width of the condyle in the experimental group were shorter than that of the control group, showing a statistical significance (p < 0.01). 2. Volumetric bone mineral density of the condyle measured by the image analyzer system in the experimental group was less than that of the control group, showing a statistical significance (p < 0.01). 3. Age-related change and chewing style-related alterations were observed in the condylar cartilage area. These findings suggested that the bone remodeling in the condyle of aged rats was considerably influenced by occlusal and masticatory alterations in addition to aging.