Effects of unilateral masticatory function on craniofacial and temporomandibular joint growth : an experimental study

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>The study was undertaken to determine effects of unilateral masticatory function on craniofacial growth and temporomandibular joint structures in young rabbits. Right-side maxillary and mandibular molars were ground out of occlusion under general anesthesia. Macroscopic measurements were made using the skulls and mandibular halves. Articular surface inclinations were determined using photographs. Positions of articular eminences on crania were determined using machine-vision technique. Changes to extracellular matrix of condylar cartilage were studied histochemically and biochemically.</p><p>Unilateral masticatory function resulted in changes in the shapes and dimensions of the mandible, maxilla and glenoid fossa. Maxillary widths, lengths of half-mandibles, and angles between the ramus and corpus were lower on the right than on the left side of each animal that had been subjected to right-side molar grinding, and in comparison with controls. As the rabbits grew, there was no recovery from the changes that had been brought about by the asymmetric function, even after occlusal function was reversed or left unmodified after a period of unilateral function. Inclinations of articular surfaces became shallower and positions of articular eminences and glenoid fossae more anterior in animals that had been subjected to molar grinding than in controls. Proteoglycan contents of condylar cartilage extracellular matrix were also affected by molar grinding: amounts of the aggregated proteoglycans in particular were low.</p><p>We concluded, that the shape and the sagittal and vertical position of the articular eminence is highly adaptive to the function of the condyle process, and that there were associated alterations in the dimensions and shapes of mandible and maxilla. Unilateral masticatory function resulted in significant changes in condylar cartilage extracellular matrix. Normal occlusion and bilaterally symmetric masticatory function during early phases of growth is important for normal development of the maxilla, mandible and articular cartilage.</p></div>