ABSTRACT
Objective:To examine the relation between the alteration of condylar endochondral in response to mandibular protrusion and the action time length by establishing a model of mandibular protrusion on young adult rats. Methods: 75 female Sprague-Dawley rats aged 9 weeks were divided into two experimental groups and one control group. In two experimental groups, bite jumping appliances created forward positioning of the condyle for twelve hours and whole day, respectively. The experimental rats, together with the control rats, were sacrificed on days 3, 7, 14, 21 and 30, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen. Results: The peak of type X collagen protein expression in 24-hour experimental groups appeared on day 21 which was on the top of all experimental groups, while in 12-hour experimental groups it was found on day 30. The results of in situ hybridization were basically in agreement with the results of immunostaining. Conclusion: Both intermittent and continuous mandibular advancement can provoke endochondral ossification in young adult rat condylar, while 24-hour ones can produce more obvious and quicker effect.
ABSTRACT
Objective:To examine the relation between the alteration of condylar endochondral in response to mandibular protrusion and the action time length by establishing a model of mandibular protrusion on young adult rats.Methods:75 female Sprague-Dawley rats aged 9 weeks were divided into two experimental groups and one control group.In two experimental groups,bite jumping appliances created forward positioning of the condyle for twelve hours and whole day,respectively.The experimental rats,together with the control rats,were sacrificed on days 3,7,14,21 and 30,respectively.Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen.Results:The peak of type X collagen protein expression in 24-hour experimental groups appeared on day 21 which was on the top of all experimental groups,while in 12-hour experimental groups it was found on day 30.The results of in situ hybridization were basically in agreement with the results of immunostaining.Conclusion:Both intermittent and continuous mandibular advancement can provoke endochondral ossification in young adult rat condylar,while 24-hour ones can produce more obvious and quicker effect.