Influence Of Increasing Occlusal Vertical Dimension On The3D Relationship Between Condyle And Fossa

Objective:Aims of this study is to discover the change of spatial condyle-fossa relationship during iOVD and compared under different OVD initial level by CBCT scanning and three dimension reconstruction of temporomandibular joints. Try to gain further understanding of the effect of clinical occlusal reconstruction on TMJs for the feedback and guidance in treatment. Methods:Two patients were selected, and both of them were in good health condition with sound tolerance. Patient A had severe wear of the dentition with a reduction in OVD, Patient B had an overerupted upper molar as a consequence of the absence of immediate restoration on the defected opposed tooth, and intrusion therapy with high temporary restoration was planned. After history collection, clinical and radiological examination and diagnosis, treatment plan was decided and informed consent was signed.After multiaspect assessment, the new OVD of Patient A was determined, which was taken as standard in full-mouth transitional restoration with composite resin. IPS emax all-ceramic prosthesis took the place of the provisional ones, since the patient well adjusted to the new OVD level after6months of adaptation.Atransitional resin restoration was placed on the defect molar of Patient B, intentionally making it high to intrude the opposing overerupted molar, expecting the extruded molar to return to its original position. When this supraerupted tooth returned to the desired position and functional occlusion reconstructed,a ceramic restoration was settled after the removal of the resin.His temporomandibular joints(TMJs) were submitted to cone beam computed tomography(CBCT) scan at closed-mouth position three times separately before the treatment, after transitional resin restoration and after ceramic prosthesis bonded. Import data into Simpleware software for image analysis. Joint spaces measurement was undergone with Kamelchuk’s method based on the joint sagittal lateral middle layer of TMJ images. Conduct three-dimensional reconstruction of TMJs during iOVD and cohere the three images with the maximum fitting of gle no id fossa internal surface. Relative movement of condyle in the fossa was observed and the results were compared with those got from the joint space measurement with two-dimensional images. We also measured the lower-face height which is determined by the distance from anterior nasal spine(ANS) to Menton(Me)and took it as a monitor of OVD. Results:Patient A rebuilt pleasant occlusion and a nice profile, after the treatment of occlusal rehabilitation. She is satisfied with the esthetics, speech and occlusion. As to Patient B, with the method of the transitional high restoration intention for intrusion, enough vertical space for ultimate prosthesis was regained by the reversion of molar overeruption in one month’s time, and an IPS e.max ceramic onlay was settled with satisfaction.By analyzing and measurement of CBCT image, we found an enlargement in posterior and superior space and a reduction in anterior space after transitional resin restoration cemented in both of the patients. The data seemed similar after the ultimate prosthesis in patient A, while they returned to the former level post-treatment in patient B.TMJ three-dimensional reconstruction with the glenoid surface maximum fitting showed that:after provisional restoration, a counterclockwise rotation was observed in the mandible with the condyle moved downward and forward in the glenoid fossa. The condyle-fossa spatial relationship of Patient A remained unchanged thereafter. However, the post-therapy image was consistent with pre-therapy image in Patient which revealed there was a recoil taking place gradually.The lower-face height measured by cep halo metric, in patient A, The data were66.9mm pretreatment,69.6mm after provisional restoration and69.4post-treatment. In patients B, The data were70.2mm, and changed into74.3mm immediately wearing the high restoration, but it turned back to70.3mm post-treatment. Conclusions:1. The increase of OVD caused by local occlusion high could be eliminated by tooth movement. High restoration on the defected opposing tooth is an effective and time-saving method for the intrusion of an overerupted maxillary molar.2. The condyle moved downward and forward in the glenoid fossa after iOVD, which might attribute to a counterclockwise rotation of lower jaw around mandibular angle, but the change is short-term reversible and the condyle can return to the original position with OVD reversion.