THE SUITABILITY OF THE EGYPTIAN BALADI SHEEP (OVIS ARIES) AS A LARGE ANIMAL MODEL FOR TEMPOROMANDIBULAR JOINT STUDIES

This study aimed to characterize and evaluate normal temporomandibular joint (TMJ) of the Egyptian Baladi sheep anatomically andhistologically as a large animal model.Fifteenheads of adult apparently healthy male sheep(Ovis aries) were utilized for;macro- andmicroscopical examination.Also, bony preparations, radiology, computed tomography and scanning electron microscopy were achieved.The TMJ consisted of mandibular condyle of the mandible,glenoid fossa of temporal bone andarticular disc in-between.The mandibular condyle was flattened laterally, convex medially and slopped caudomedially.The glenoid fossa was elliptical in shape, concavoconvex from backward to forward.The disc was a smooth, elliptical plate,biconcave,thin centrally and thick peripherally with sloped end caudomedially.Histologically, the ?brocartilage layer of the condyle and glenoid fossa was differentiated into fourzones; fibrous, proliferative, hypertrophic, and calcificationzones.The?brocartilagenousdisc consisted of thick densely packed bundles of collagen fibers with chondrocytesin-between.The complex architecture of articular disc fibers wasrevealed by light and scanning electron microscopic examination. The collagen ?bers orientation was perpendicular in the anterior and posterior regions, and parallel anteroposterior in the central region.There were many anatomical similarities between sheep and human TMJ in; relations, size, shape, position of the disc,histological structureandsurgical approach. Furthermore, the sheep are more economic, available by large numbers, high ethical suitability,all this renders the sheep not only suitable but ideal choice as a large animal model over other animal models.