Experimental studies of healing process of rat mandibular condylar fracture, using 45Ca as tracer

The cervical region of the mandibular condylus of young rats was fractured. The healing process was observed pathohistologically, autoradiographically using 45Ca as a tracer, and by ultra soft roentgenography. Condylectomy of the mandibular condylus was done at the same time and its regeneration observed. The results of the observation are as follows: The fractured portion is bonded with the soft tissue 1 - 2 weeks postoperatively. Histologically, new-blood vessels in the granulation tissue and the connective tissue's change into fibers are seen. On the second week chondrocytes appeared in the neck of the capitulum mandibulae and the stump of the ascending branch. On the 3rd postoperative week, the stump of the fracture of the bone is bonded with proliferated cartilaginous tissue and an osseous bond was seen in part by autoradiograph and ultra soft x-ray picture. New bone due to periosteal ossification is seen around the stump on the ascending branch side, and the bone reconstruction with osteoclasts was seen in the inside the trabeculae. On the 4th postoperative week, osseous concrescence is observed in the fractured portion. Regeneration of the capitulum mandibulae after extirpation of the capitulum mandibulae is seen in all the cases. On the postoperative 12th week, the macroscopic form of the degenerated capitulum mandibulae which seemed to be excessive becomes almost the same morphologically with that of the contralateral side and it was observed histologically that the construction of the capitulum mandibulae is completely restored. (J.P.N.)