An in vivo evaluation of fit of zirconium-oxide based ceramic single crowns, generated with two CAD/CAM systems, in comparison to metal ceramic single crowns.

PURPOSE: The purpose of this study was to assess in vivo the marginal fit of single crowns produced using two CAD/CAM all-ceramic systems, in comparison to more traditional metal ceramic crowns. MATERIALS AND METHODS: Thirty vital, caries-free, and previously untreated teeth were chosen in five patients who needed extraction for implant placement and therefore were included in this study. In the control group (C), 10 regular metal ceramic crowns with porcelain occlusal surfaces were fabricated. In the other two groups (Z and E), CAD/CAM technology was used for the fabrication of 20 zirconium-oxide-based ceramic single crowns with two systems. All zirconia crowns were cemented with glass-ionomer cement, always following the manufacturer's instructions. The same dentist carried out all clinical phases. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at a magnification of 50×. On completion of microscopic evaluation, representative specimens from each group were prepared for ESEM evaluation. Mean and standard deviations of the four landmarks (mesial, distal, buccal, palatal) at each single crown were calculated for each group. Multivariate analysis of variance (MANOVA) was performed to determine whether the four landmarks, taken into consideration together, differed between groups. Two-way ANOVA was performed to study in detail, for each landmark, how the three systems used to produce the FPDs affected the gap measurements. Differences were considered to be significant at p < 0.05. RESULTS: MANOVA revealed no quantitative differences of the four landmarks, when taken into consideration together, between the three groups (p < 0.0001). Two-way ANOVA, performed at each landmark, revealed no quantitative differences between the three groups (p < 0.0001 for each landmark). CONCLUSIONS: Within the limitations of this study, it was concluded that the two zirconium-oxide-based ceramic CAD/CAM systems demonstrated a similar and acceptable marginal fit when compared to more traditional metal ceramic crowns.

The one-model technique: a new method for immediate loading with fixed prostheses in edentulous or potentially edentulous jaws.

This article examines a new prosthetic procedure for the immediate loading of implants with a fixed prosthesis in edentulous or potentially edentulous arches. In these situations, one of the main problems associated with immediate loading is the transfer of diagnostic information to the master cast. This technique takes advantage of an acrylic resin transfer plate that enables transfer of the study cast information to the master cast. Without any intrasurgical impression or any recording of the maxillomandibular relationship during or after surgery, construction of an adequate esthetic and functional fixed prosthesis is possible on the basis of diagnostic information acquired in the presurgical phase. The methodology is always applicable when there is an indication for immediate loading of implants. The rationale and guidelines for the successful use of this technique in edentulous or potentially edentulous arches are discussed and illustrated with a clinical case.