Effects Of Condylar Neck Ostrotomy On Growth And Development Of Mandible In Rats

[Objective] To investigate the effects of condylar neck osteotomy on condyle and mandible in a rat model and to provide scientific basis for research of normal development of maxillofacial region.[Methods] Unilateral condylar process osteotomy was performed on four weeks old SD (Sprague-Dawley) rats using a special blood vessel forceps and unilateral condylar process fracture was performed using an eye scissors.Operation and contralateral side of osteotomy,operation side of fracture and un-operated blank control group were set up.All of the rats were killed after 1,3,5, or 9 weeks.The measurement,imageology and histology observation of condylar process were observed.Expression of connective tissue growth factor (CTGF) which associated with development, and type X collagen (ColX) which associated with osteogenic characteristics were examined by immunohistochemical staining.[Results] After osteotomy of 1 week,the condylar of operation side was compensatory enlargement.The growth and development of mandible in osteotomy side was limited in the four times after osteotomy operation.The height of mandibular ramus in osteotomy side was limited which was compared with the operation side of fracture,and the height of the mandibular ramus, the length and height of the mandibular in contralateral side of osteotomy were growth more than the operation side.HE staining showed that the thickness of chondroblast zone (CZ) and the hypertrophic zone (HZ) in osteotomy side was compensatory enlargement after 1 week,and then became diminish.The fibrous zone (FZ) was thickening more than other groups after 5,9weeks.Immunohistochemical staining show that CTGF and Col X was expressed in proliferative layer, chondroblast layer and hypertrophic layer of the condylar cartilage.Quantitive analysis showed that CTGF expression in the operation side of osteotomy after 1,3,5weeks.was increased and Col X expression was increased after 1 week.[Conclusions] This rat model of the condylar neck osteotomy shows great practicability and reproducibility. The osteotomy compared with the fracture produces a series of physical responses in the mandibular and condyle and lead to asymmetry of them in rats. It also has effect on the expression of CTGF and collagen type X in condylar cartilage.