Modification of condyle anatomy following a monolateral bite rise: a histological study in rat

The aim of this study is to evaluate the histologic modifications of rat articular capsules, after compression and strain. Fifty adults Sprague Dawley rats were used in this study. The rats were divided into 3 groups: a dysfunction group, treatment group and a Control group. In the rats in the first two groups an occlusion hump, made of composite and less than 0.5 mm high, was applied to the upper right molar. The rats were anesthetized with an intraperitoneal injection of benzodiazepine (0.5-1 mg for 100 g. of body weight). The composite used consisted of a hollow, plastic cylinder 0.5 mm high, spread over the whole occlusal surface of the right upper molar. The dysfunction group therapy wore the occlusion hump for a week, at the end of which the animals in this group were killed and their temporomandibular joint removed. In the treatment group a second occlusion hump was applied to the left upper molar, in order to obtain a distraction of the previously compressed temporomandibular joint. The rats of the second group wore the second occlusion hump for one week. The rats were then killed with an intraperitoneal injection of Tanax, and the block sections, containing the temporo-mandibolar joint, were retrieved with a diamond disk, and surrounding tissues were washed in saline solution and immediately fixed in 4 percent formalin for 4 days. In the control group, no treatment was applied. In the first group, bone resorption was observed in the left temporomandibular joint; no osteoclast were, however, present. No other tissue alterations were present. Newly formed bone undergoing remodelling was intensely stained with acid fuchsin. In the second and third groups, no bone remodelling areas were observed. In conclusion, the compression of the temporomandibular joint determined a remodelling of the bone structure of the condyle.