[Expression of bone histomorphometry parameters in rabbit condyle during mandibular forward positioning].

OBJECTIVE: To observe the changes of bone histomorphometry parameters in condyle of rabbits during mandibular forward positioning. METHODS: Forty rabbits with eight weeks of age were simple randomly divided into the experimental group (n = 24) and control group (n = 16).Mandibles of rabbits in the experimental groups were induced to forward position by a functional appliance.The experimental group and control group were sacrificed after 2 and 4, 8, 12 weeks.The specimens from right tempromandibular joints were processed for undemineralised sections.These sections were used for fluorescent microscopy observation and the measurement of bone histomorphometry. RESULTS: At 8 week bone-volume fraction [(75.83 ± 1.10)%], trabecular thickness [(103.28 ± 2.89) µm], trabecular number [(2.86 ± 0.06) mm(-1)], mineral apposition rate [(2.32 ± 0.02) µm/d] and index of osteoblast [(30.20 ± 0.47) N/mm(2)] in subchondral region of the cartilage in the experimental group were significantly increased compared with the age-matched controls [respectively (64.00 ± 1.54)%, (87.00 ± 1.13) µm, (1.84 ± 0.08) mm(-1), (1.69 ± 0.02) µm/d and (21.07 ± 0.59) N/mm(2)] (P < 0.05). However, trabecular separation [(170.00 ± 2.25) µm] was lower than those in the controls [(241.50 ± 1.57) µm] with significant difference(P < 0.05). There was no significant difference in the bone histomorphometry parameters of the central region between the experimental group and the age-matched control group (P > 0.05). CONCLUSIONS: The pattern of bone histomorphometry parameters expression in subchondral region has a high correlation with the adaptive remodeling of the condyle after functional appliance.