The Study Of Occlusal Contacts And Mandibular Border Movement Traces In Patient With Unilateral Molar Buccal Crossbite

Objective The unilateral molar buccal crossbite patients as subjects were selected and Occlusal analysis system and mandibular border movement analysis system were applied for this study, to observe the characteristics of the mandibular border movement traces and bilateral occlusal crossbite in patients with unilateral molar buccal crossbite and to compare the difference with the individual normal occlusion. There were two methods to investigate the effect of the unilateral molar buccal crossbite to the mandibular border movement traces and bilateral occlusal crossbite, in order to find harm the unilateral molar buccal crossbite on TMJ and stomatognathic system, and to guide the clinical design and evaluate the clinical efficacy of treatment programs.Method Eighteen patients with unilateral molar buccal crossbite patients were selected as the experimental group, ten volunteers with individual normal occlusion were selected randomly as the control group.The data of center occlusion and occlusal time and the distribution balance degree of occlusal force of experimental group and control group were recorded with T-ScanⅢ system in intercuspal position, and compared with individual normal occlusion, the traces of mandibular incisor point and the rage of mandibular incisor point movement and the symmetry of condylar movement were tested by ARCUSdigma Ⅱ system, and to compared with individual normal occlusion. The results of two groups were analyzed with statistical methods by SPSS17.0.Results (1) The center of force of the experimental group changed larger than the control group, the end point of center of occlusion force located outside of the white oval in intercuspal position. The distance between center line, the occlusal time and the distribution balance degree of occlusal force of experimental group were longer than those in the control group and there were Significant differences between them (P<0.05).(2) The mandibular border movement traces of incisor point were rugged and large fluctuation in experimental group; Protrusive border movements in experimental group were less than that in control group (p<0.05). Lateral movement of buccal sides were different significantly with control group (P<0.05); Maximum remainder of bilateral condylar movements (MRC) of opening movement (anterior-posterior) and protrusive movements (vertical and anterior-posterior) were different significantly with control group (P<0.05).Conclusion (1) The characteristic of occlusal contacts in patients with unilateral molar buccal crossbite have significant differences with individual normal occlusion. Its occlusal stability is no better than individual normal occlusion. Therefore, the unilateral molar buccal crossbite has a potential effect on the normal oral occlusal function.(2) The unilateral molar buccal crossbite can affect feature and range in mandibular border movements of incisor point, and affect symmetry of condylar movements. It has significant differences with individual normal occlusion. Therefore, the unilateral molar buccal crossbite has a negative effect on the normal mandibular movement function.(3) This finding of study indicate that the unilateral molar buccal crossbite has an effect on the symmetry and normal movement of condylar and stability of temporomandibular joint.