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ePaper created 2018-05-16, 11:45:19 | version 1.38.0
Fig. 5 Anterior relationship in the musculoskeletally stable position. The mandible now rested in a posterior rela- tionship to the maxilla, guided by the masticatory muscles (compare with Figure 3). Figs. 6a & b The anterior deprogrammer was used to register the new relationship of the mandible against the maxilla, the musculoskeletally stable position. Fig. 7 The increase in the VDO was designed according to functional and esthetic needs that were evaluated during the mock-up stage. In this detailed view of the mock-up, the increased length of the anterior teeth can be appreciated. Fig. 8 Minimal preparation of posterior teeth for IPS e.max monolithic onlay restorations. Preservation of enamel is of primary importance and since the VDO was being increased, the preparation of the masticatory surfaces was limited. Since the molars had no antagonists on the mandible, only the pre- molars were initially treated. Fig. 9 The final restorations were fully digitally manufactured. Intraoral scanning with TRIOS 3 and CAD/CAM fabrication of the monolith- ic onlays from IPS e.max lithium disilicate material. Fig. 5 Fig. 6a Fig. 6b Fig. 7 Fig. 8 Fig. 9 Should the vertical dimension of occlusion be changed? Which should the treatment position be? In a bruxing patient, usually the VDO re- mains stable even though the wear of the dental tissue might be significant. This is mainly a result of continued tooth eruption compensating for the loss of dental tissue. The prosthetic space is limited and often the vertical dimension needs to be in- creased in order to gain the prosthetic space needed for the final restorations. The amount of increase is determined by the freeway space and by the esthetic and functional analysis of the case during the diagnostic stage, during which all the infor- mation is gathered and analyzed. Fabrica- tion of an analytic wax-up for the recon- struction of a functionally and esthetically adequate tooth morphology and predefi- nition of the reconstructed tooth is essen- tial. The diagnostic wax-up needs to be re-evaluated intraorally in the try-in stage of mock-up. The esthetic analysis will de- termine the inclination and position first of the incisal edge and second of the occlusal plane. This will also help the clinician to de- cide in which dental arch (if not both) the increase in VDO should be performed. In this case, it was decided to increase the VDO in the maxillary arch (Fig. 5). Mono- lithic onlay restorations fabricated from IPS e.max CAD lithium disilicate blocks (Ivoclar Vivadent) were used on the premolars (Figs. 6a & b). The reason for restoring only the premolars with final restorations was that the molars presented with failing old resin restorations; therefore, definitive res- torations would be implemented in differ- ent stages. At this stage, only composite onlays were placed over the existing resto- rations on the molars in order to stabilize the occlusion. The composite onlays were made based on the transparent silicone matrix of the diagnostic wax-up. Since the VDO needed to be increased, the future treatment position needed to be established. The maximum intercuspa- tion that the patient presented with was an inadequate treatment position and was not to be maintained. He also had more than one bite, making it uncomfortable, especially because the anatomy of the masticatory surfaces was compromised due to wear. The new treatment position should be reproducible and stable through- out the treatment. Of equal importance is the maintenance of the stability of this treatment position after the finalization of the case. It has to be a functional one based on normal function without strain of any of the structures of the stomatognathic system. The new 3-D position in which the mandible will rest against the rest of the cranium should be dictated by the masti- catory muscles during their rest position. This treatment position is called the mus- culoskeletally stable position. It is similar to the centric relation, but it is not as exact about the intracapsular condyle position (the debate about the definition of centric relation is still under considerable discus- sion even currently). Rather, it allows the masticatory muscles to dictate the position of the mandible regardless of the condylar position. Therefore, it is a position highly individualized to each patient and his or her distinctive anatomical and functional char- acteristics. This position is determined initially with the stabilization appliance. In order to record this position, we use an anteri- or deprogrammer (Fig. 7). Compared with jaw manipulation, this device is a predictable way to record the musculo- skeletally stable position, since it does not depend on the patient relaxing to 78 — issue 2018 Clinical Mentoring Article