The Response of Condylar Cartilage Stimulated by a Small Defect in the Rat Mandible

Abstract

This study investigated the response of the condylar cartilage subjected to a small bone defect as a local stimulus in the rat mandible, in order to clarify one of the mechanisms of condylar cartilage growth. Fourteen male Wistar albino rats weighing 200 to 260 gm were divided into two groups, with two animals in a pilot study and 12 animals in the experimental group. Five male Wistar albino rats weighing 400 to 540 gm were used in a third group, which provided a basis for comparisons with the experimental group. To evaluate bone growth changes of the rat mandible, a superimpositioning method of tracings of the left and the right mandibles was done using the molars, incisors, anterior and inferior borders of the mandible. A sliding micrometer was used to measure each distance between the posterior edge of mental foramen (MF) and the posterior border of condylar process (CP) or angular process (AP). In the pilot study, one of two animals showed a decreased angular process and an increased condylar process, and the results suggested that the decreased activity of the masseter, resulting from dissecting a part of the masseter, may play an important role in changing the size or the shape of the rat mandible. In the experimental study, the masseter was not dissected and the results indicated that a hole drilled at the condylar notch did not stimulate condylar growth enough to be measurable. The third group showed that there were minor asymmetries between the left and the right mandible in normal rats, ranging from 0.49 to .0297 mm. Therefore, a larger sample size would be needed to arrive at definite conclusions.