A fully digital approach to replicate peri-implant soft tissue contours and emergence profile in the esthetic zone.

OBJECTIVE: This short communication reports on a novel digital technique designated - the "Fully Digital Technique (FDT)" - to take the impression of the peri-implant soft tissue and emergence profile with an intraoral scanner, digitally capturing both the three dimensional position of the implant platform and the coronal and gingival parts of the provisional retained restoration. MATERIALS AND METHODS: A first intraoral digital impression, which generated a standard triangulation language file (STL1), was taken using a standardized implant scanbody to detect the position of the implant. A second digital impression (STL2) with the provisional retained restoration in situ was performed in two steps: the first part of the scan captured all details of the vestibular and palatal sides of the provisional retained restoration and the adjacent teeth. The provisional retained restoration was then unscrewed, and the subgingival part of the restoration was scanned directly out of the mouth to determine its subgingival shape. STL1 and STL2 were imported into imaging software and superimposed using the "best fit" algorithm to achieve a new merged file (STL3) with the 3D implant position, the peri-implant mucosa, and emergence profile. The merged file was used to design the CAD/CAM customized abutment and to realize a stereolithographic model by 3D printing. RESULTS: The STL superimposition of digital impressions of the implant position and the provisional retained restoration constitute a novel technique to obtain a single STL file with the implant position and its peri-implant mucosal architecture. CONCLUSIONS: FDT is a rapid digital approach for achieving all information of the peri-implant soft tissue and emergence profile directly from the provisional retained restoration.

Effect of resin cement space on the fatigue behavior of bonded CAD/CAM leucite ceramic crowns.

This study evaluated the influence of occlusal resin cement space on the fatigue performance of bonded-leucite crowns to a dentin-analogue material. Leucite anatomical crowns were adhesively cemented to dentin-like preparations having distinct occlusal cement space (50, 100 and 300 µm) (n = 18), and subjected to step-stress fatigue testing (150 N - 350 N; step-size: 25 N; 20,000 cycles/step; 20 Hz). Fatigue data (load and number of cycles for failure) were analyzed using Kaplan-Meier and Mantel-Cox (log-rank) tests (p <0.05). Fractographic analysis and occlusal internal space measurements were also performed. There was no significant difference for the distinct occlusal cement layer (50 µm: 289 N, 136,111 cycles; 100 µm: 285 N, 132,778 cycles; 300 µm: 246 N, 101,667 cycles). Occlusal internal space analysis showed a mean thickness of 120.4 (50 µm), 174.9 (100 µm) and 337.2 (300 µm). All failures were radial cracks originating at the ceramic-cement interface. Distinct occlusal cement spaces had no effect on the fatigue behavior of anatomical leucite crowns.

Evaluation of the accuracy and stress distribution of 3-unit implant supported prostheses obtained by different manufacturing methods.

The purpose of this in vitro study was to measure the vertical, positive-horizontal, and negative-horizontal misfit (VM, PHM, and NHM, respectively) of the zirconia three-element prosthetic framework, fabricated using different methods, and compare them with conventional fabrication methods (lost-wax casting). Furthermore, this study aimed to evaluate the influence of the misfit values on the biomechanical behavior of the 3-unit fixed prosthetic frameworks using three-dimensional finite element analysis (3D-FEA). Forty frameworks (n = 10) were fabricated as follow: G1, Cerec Bluecam; G2, iTero; G3, 3Series; and G4, conventional method. The samples were randomized to measure marginal misfit using a high-precision three-dimensional (3D)-optical microscope. The results were submitted to analysis of variance (ANOVA), with the significance level set at 5%. The mean VM values of each group were used in creating the models by 3D-FEA with the misfit found in optical microscopy. The programs used were the InVesalius, Rhinoceros, SolidWorks, FEMAP and NEiNastran. The von Mises map was plotted for each model. The G4 showed the lowest mean VM value (16.73 µm), followed by G3 (20.71 µm), G2 (21.01 µm), and G1 (41.77 µm) (p < 0.001). G2 was more accurate than G1 (p < 0.05) and similar to G3 (p = 0.319). For PHM, G4 was the most accurate and did not present overextended values. With regard to NHM, the computer-aided design and computer-aided manufacturing (CAD-CAM) systems were more accurate (-61.91 µm) than G4 (-95.36 µm) (p = 0.014). In biomechanical analysis, stress concentration caused by oblique loading is greater than caused by axial loading. In axial loading, G4 was the most favorable while G1 was the least favorable, biomechanically, in oblique loading, similar stress patterns were observed in all the models. The prosthetic screw was the most overloaded structure, but the material did not influence the stress distribution. The misfit prostheses showed a greater degree of stress than the controls (without misfit). The manufacturing method influenced the marginal misfit of the frameworks, with the conventional method being the most accurate and the Cerec Bluecam System (closed system) the least accurate. Biomechanically, fitting prostheses were more favorable than misfit prostheses.

A fully digital approach to replicate functional and aesthetic parameters in implant-supported full-arch rehabilitation.

PURPOSE: The aim of this technical procedure was to use a fully digital technique (FDT) for full-arch implant support rehabilitation. The FDT was used to transfer the provisional restoration parameters to definitive restorations using intraoral scanners. METHODS: Three sets of digital impressions were obtained. Through the first set, standard tessellation language 1 (STL1), provisional restorations screwed to implants and the surrounding gingival tissue was captured. STL2 consisted of intraoral scans of standardized scanbodies screwed to implants to collect 3D positioning data of implants. STL3 included the digital impression of provisional restoration out of the mouth in order to capture the gingival architecture and the peri-implant soft tissue that was not possible to transfer with the previous impressions. STL1, STL2, and STL3 were combined using computer-aided design (CAD) functions into a single file, STL4. Thus, STL4 contained information on the 3D implant positions, soft tissue architectures, occlusal relationships, correct occlusal vertical dimension and aesthetic features. Using STL4, the master models with implant analogues were 3D printed. Computer-aided design and computer-aided manufacturing milled (CAD/CAM-milled) aluminium bars and a resin prototype were produced to test the accuracy and the functional and aesthetic parameters. Titanium frameworks were digitally designed using STL4, milled using CAD/CAM, and finalized with pink resin and resin teeth. CONCLUSION: The FDT provided an effective fully digital protocol to capture all information for provisional full-arch implant restorations using an intraoral scanner and transfer that information to definitive restorations.