Comparison between Two Different Fixation Techniques on Experimentally Induced Unilateral Subcondylar Fracture in TMJ of the Dogs (Histopathological and Histomorphometrical Study)

Abstract

Objectives: The present study was performed to compare between two different fixation techniques and evaluate the histopathological changes which occur in temporomandibular joint (TMJ) of the dogs after surgically induced unilateral subcondylar fracture. Methods: Twenty- One healthy beagle male dogs with a mean age of 30 months were used in the present study. One of these animals was sacrificed to study the normal histology of the dog TMJ. The rest of the animals (20 animals) were operated on to induce a displaced unilateral subcondylar fracture then, the animals were randomly equally divided into 2 groups. After surgery, 5 dogs of each group were sacrificed at 2 months after surgery (Short-Term), while the remaining 5 were sacrificed at 4 months after surgery (Long-Term). The heads were separated and fixed, oscillating saw was used to articulate the entire TMJ. Specimens were decalcified, then the specimens were washed, grossed and sectioned in a sagittal plane. Tissue sections of 4 um thick were cut and stained with Hematoxylin and Eosin to be studied microscopically. Results: In group I animals, at 2 months after surgery, there was a marked hypertrophy of the articular fibrous covering of the condylar head, while at 4 months after surgery, the articular fibrous covering appeared thinner than normal, with marked decrease in thickness of the articular cartilage layer. In group II, at 2 months after plate insertion, the articular fibrous covering became hypertrophic, and the articular cartilage was markedly reduced but it was of a uniform thickness, while at 4 months after subcondylar fracture and plate fixation, no significant changes could be detected either in thickness or structure of the articular fibrous covering. Conclusion: Based on this study, it is obvious that the plate fixation group gave the most favorable results, when compared with maxillomandibular fixation (MMF) group.