Intraoral splints are a commonly used dental treatment for a variety of conditions. Because such splints alter the condyle-disc-fossa relationship, they probably change the loading status of the temporomandibular joint (TMJ), including the TMJ disc. Collagen, a major constituent of the disc, acts to resist tensile loading, and it is presumed that the fiber orientations of the individual disc bands reflect their functional loading. Therefore, the purpose of this study was to examine effects of intraoral splint wear on TMJ morphology in general, and collagen orientation of the intra-articular disc in particular. Young adult, female miniature pigs were divided into three groups: open-bite splint, protrusive-bite splint, and unsplinted control. Splints were worn for 2 months, after which the TMJ discs were harvested for histological examination and stereological analysis, and the skulls were cleaned. Although the splints had no effect on skull dimensions, changes were seen in the TMJs. The discs of the protrusively-splinted group showed an increased thickness of the posterior band (P Ͻ 0.015) and minor changes in collagen orientation of the anterior band. The most striking change was the presence of a degenerative osseous defect on the medial side of the mandibular condyle in half of the splinted animals. These results indicate that prolonged splint wear can induce remodeling and even injury of TMJ tissues. Anat Key words: temporomandibular joint disc; porcine; morphology; intraoral splints; collagenIntraoral splints are used in dentistry to treat a variety of conditions, such as occlusal malalignments, temporomandibular joint (TMJ) dysfunctions, and sleep apnea (Bondemark, 1999;Carels and van der Linden, 1987;Gianelly et al., 1970;Grim, 1995;Johal and Battagel, 1999;Kimmel, 1994;Major and Nebbe, 1997;Nitzan, 1994;Wright et al., 1995). All splints change the occlusal relationship of the teeth and, hence, the spatial relationship of the TMJ components, although the precise effect varies with the splint (Ito et al., 1986). Additionally, splint wear must affect disc structure, as indicated by studies showing changes in shape (Ferrari and Herring, 1995) and glycosaminoglycan (GAG) content (Mao et al., 1998;Sindelar et al., 2000). However, detailed morphology has not previously been assessed.The TMJ disc is composed of approximately 80% water (Sindelar et al., 2000); the remaining 20% is mostly collagen. Prior studies on the human, bovine, dog, rabbit, monkey, sheep, and rat TMJ disc have shown that the fibers of the intermediate zone are oriented predominantly in the anterior-posterior (AP) direction, while the fibers of the anterior and posterior bands are more multidirectional or "basket-woven"
The stability of free convection in an annulus is governed by the boundary conditions on the inner and outer walls of the annulus and the upper and lower boundaries. This paper explores the effect of free convection on the inner surface of the annulus, where the boundary conditions for the outer wall and the upper and lower boundaries are controlled. The temperature is measured in the center of the air cavity and just below the surface of the inner annular boundary. Experimental results are shown for a radius ratio of 0.40, aspect ratio of 20.7. These more recent experimental results are compared to prior work for a radius ratio of 0.60, aspect ratio of 31.0. The results indicate that as the Rayleigh number is increased, the flow experiences a transition from steady flow to a very regular oscillatory flow, and then a supercritical Hopf bifurcation as the flow finally transitions to chaotic behavior. Proper orthogonal decomposition analysis is presented as a method for quantifying the complex dynamic behavior of the system.
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