Experimentally Created Nonbalanced Occlusion Effects on the Thickness of the Temporomandibular Joint Disc in Rats

Abstract

Objectives:To test the hypothesis that experimentally created physiologically nonbalanced occlusion will not affect the thickness of the temporomandibular joint (TMJ) discs in rats. Material and Methods: Twenty-four 8-week-old Sprague-Dawley rats were equally divided into a control group that was left untreated and an experimental group where a nonbalanced occlusion was created. Elastic rubber bands, 1 mm in diameter, were inserted and 1 week later were replaced by plastic material between the first and the second molars of the left maxillary and the right mandibular dentitions to move the first molars about 0.8 mm mesially. This created and maintained a physiologically nonbalanced occlusion. The animals were euthanized 8 weeks later, and the TMJ disc thickness was measured on histologically prepared slices using an electronic meter. Two-way univariate analysis of variance was used to compare the groups (␣ level ϭ .05). Results:The intermediate zone was thicker in the experimental group than in the control group (P ϭ .003), but no differences were found between groups regarding the anterior and posterior bands. There were no significant sex-related effects on this observation. Conclusion:The hypothesis is rejected. The results indicate that the intermediate zone of rat TMJ disc has the ability to adapt to the alteration of the space between condyle and fossa caused by occlusion changes. Further studies on larger groups that are followed for longer times are needed. (Angle Orthod. 2009;79:51-53.)

Death and proliferation of chondrocytes in the degraded mandibular condylar cartilage of rats induced by experimentally created disordered occlusion

“…For rats in the experimental group, the first left maxillary and the first right mandibular molars were moved medially as previously described [27]. Briefly, an elastic rubber band (3 M Unitek, 1/8#), about 1 mm in diameter, was inserted between the first and second left maxillary molars and between the first and second right mandibular molars.…”

Sustained Inflammation Induces Degeneration of the Temporomandibular Joint

“…Two blinded examiners separately measured disc thickness for the anterior band, intermediate zone, and posterior band in 10 randomly selected sections per joint, with the averages pooled (N = 6/group). The longest linear distance was measured for the anterior and posterior bands, but the shortest distance was measured for the intermediate zone (Sun et al, 2009 …”

Comparison of the position of the mandibular fossa using 3D CBCT in different skeletal frames in human caucasic skulls

“…It is also suggested that the position of the MF could be influenced by the function of the condyle or an influence of the mandible [12,16,22,23,30]. Also, the influence of the dental function is described as a possible modulator of the continuous alteration of the morphology of the TMJ [15,36,45]. Some differences in the position between different dentoskeletal frames and its influence as a possible etiological factor in the development of malocclusion have been previously reported by some authors using 2D analysis with linear measurements or using geometric morphometrics.…”