As a secondary cartilage, the condylar cartilage of the mandible is known to be responsive to extrinsic stimuli of local biomechanical origin. The purpose of this study was to study the effects of the mandibular joint to the loss of incisal
function in
the rat.
Seventy five 21-dya-old male rats(Sprague-Dawley strain) were divided into three groups and each groups were subdivided into 1, 3, 7, 14 and 21 days groups. In incisor clip group, both the maxillary and the mandibular incisor teeth were trimmed
bilaterally to the level of the gingiva every other day. The soft diet group was fed a soft diet consisting of mush or thick soup. The third group of untreated rats fed normal rat pellets constituted the control group. At 90 minutes prior to
sacrifice,
all rats were injected intravenously with 1μCi/g body weight of [³H]-thymidine (Amersham UK. Specific activity=2 Ci/mmol). The animals were killed at 1, 3, 7, 14, 21 days and the TMJs were prepared for the histologic, histomorphometric and
biochemical
analysis.
@ES The results were as follows:
@EN 1. Both the incisor clip and soft diet groups exhibited reduced size and density of bony trabeculae underlying the condylar cartilage and retarded osteogenesis.
2. The thickness of the prechondoblastic layer of the condylar cartilage was increased for the experimental period inn all groups.
3. The thickness of prechondoblastic layer of superior portion of the condylar cartilage in both experimental group and that of posterior and posterosuperior portion in only incisor clip group were significantly reduced compared to the control
group.
4. For all periods, incorporation of ³H-thymidine was significantly decreased compared to control group in the incisor clip group, and soft diet group exhibited intermediate incorporation value between the control and incisor clip group.
These results suggested that the loss of incisal function by incisor clip and physical consistency of diet may have and effect on growth of the mandibular joint.
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