Effects of mandible functional lateral shift on proliferation activity of condylar cartilage

Abstract:

Objective：To study the effect of functional shift on proliferation activity of condylar cartilage among pubertal rats. Methods：Eighty Sprague-Dawley rats of 28 d were randomly divided into three groups：shift group（n=40），recovery group（n=20），control group（n=20）. Rats in shift and recovery groups were imposed with crowns on incisors causing mandible shift 2 mm to the left .The appliance was removed after 2 weeks in recovery group. Ten and five rats were killed on the 7th，14th，21st，28th d separately in shift group and control group. Ten rats in recovery group were killed on the 7th and the 14th d after the crowns being removed. Proliferating cell nu－clear antigen（PCNA） expression was detected by immunohistochemistry. Results：（1）PCNA cells mainly distributed in the proliferating cell layer. （2）On the 7th d，PCNA expression was increased in the posterior，central and external regions of the contralateral side in shift group（Pcentral=0.022，Pposterior=0.019，Pexternal=0.024）；while it was significantly decreased in the posterior and external region of the ipsilateral side in shift group（Pposterior=0.015，Pexternal=0.017）. On the 14th d，the differences observed on the 7th d became more obvious（contralateral side：Pcentral=0.0023，Pposterior=0.01，Pexternal=0.0097；ipsilateral side：Pposterior=0.0005，Pexternal=0.006）and lasted to the 28th d.（contralateral side：Pcentral=0.0001，Pposterior=0.0001，Pexternal=0.0001；ipsilateral side：Pposterior=0.0001，Pexternal=0.0001）. In recovery group，PCNA expression in all regions generally recovered to the level of the control group. Conclusions：The mandible functional shift in pubertal rats may cause asymmetric condyle remolding. Condyle remolding gradually recovers to normal in recovery group after early treatment.