Effect of Adhesive Gap Setting on Fracture Resistance of All-ceramic Crowns

Background: Several factors might affect the fracture resistance of all-ceramic crowns, including cement thickness. Aim: To evaluate the influence of cement thickness on the fracture resistance. Objective: To determine the effect of varying the adhesive gap thickness on the fracture loads of all-ceramic CEREC 3D molar crowns. Methods: Standardized prepared epoxy resin molar dies (Viade Inc.) were fabricated. A standard molar crown was designed using a CEREC 3D machine (Sirona Dental Systems). Twenty-four crowns were milled from Vita Mark II blocks (Vita Zahnfabrik), using adhesive gap settings of 30, 60 and 90 µm (n=8). A dual-cure resin cement (PanaviaF 2.0, Kuraray) was used to cement the crowns to their respective dies, following manufacturer's recommendation. After 1 week of storage in distilled water at 37°C, each crown was loaded in compression until complete failure in a universal testing machine (Instron 8501) and fracture loads (N) were recorded. Fractured specimens were sectioned to determine cement thickness. Sections were examined using a traveling light microscope to measure cement thickness. Data were statistically analyzed using one-way ANOVA test and Pearson's correlation at (α=0.05). Results: The mean fracture loads and standard deviation values in N were 1,267.57 (122.82), 1,225.20 (179.46) and 1,180.76 (161.77) for the crowns with 30, 60 and 90µm, respectively. ANOVA indicated no significant differences among mean fracture strength values (p = 0.55). All crowns failed in a catastrophic mode and were not repairable. Conclusions: Adhesive cement gap as achieved with three CEREC 3D settings from 30 to 90µm had no significant effect on fracture strength of crowns made from Vita Mark II blocks.

Different Methods for Inlay Production: Effect on Internal and Marginal Adaptation, Adjustment Time, and Contact Point

SUMMARY The aim of this study was to evaluate the effect of different production methods of resin and ceramic inlays on marginal and internal adaptation, adjustment time, and proximal contacts. Forty premolars were selected, embedded (their roots), and prepared to receive inlays that were made as follows (n=10): LaRe—digital impression with a Lava C.O.S. scanner, followed by milling of Lava Ultimate block (composite resin) in a milling center; CeRe—digital impression with a Cerec 3D Bluecam scanner, followed by milling of Lava Ultimate block in Cerec; CeDis—digital impression with a Cerec 3D Bluecam scanner, followed by milling of IPS e.max CAD block (lithium disilicate) in Cerec; and PresDis—impression with polyvinyl siloxane, inlay made using the lost wax technique and IPS e.max Press pressed ceramic (lithium disilicate). Marginal and internal adaptations were measured using the replica technique. The inlay adjustments were performed using diamond burs in a contra-angle hand piece, and the time for adjustment was recorded using a timer, in seconds. The tightness of the proximal contact was measured using standardized metal blades. The statistical analyses for marginal fit data showed that at the cervical edge, CeDis (177.8 μm) had greater misfit than CeRe (116.7 μm), while all the groups had similar adaptation at the occlusal edge. The groups had similar internal fit at the pulpal wall, while LaRe (104.7 μm) > CeDis (66.7 μm) = CeRe (76.7 μm) at the axial wall. The groups restored with lithium disilicate ceramic took more time for adjustment when compared to the resin restorative material. The lowest proximal contact, in micrometers, was seen in the CeRe group (8.8 μm).

In vitro evaluation of the fracture strength of all-ceramic core materials on zirconium posts

ABSTRACT Objective: For most endodontically treated teeth, tooth-colored post-core systems are preferable for esthetic reasons. Therefore, improvements in material strength must also consider tooth colored post-core complexes. The objective of this study was to evaluate the difference in tooth colored post-core complex strengths. Materials and Methods: A total of 33 human maxillary central incisor teeth were used for this study, with three groups of 11 teeth. Three different methods were used to fabricate all-ceramic post-core restorations: zirconia blanks, Cerec 3D-milled to one-piece post-core restorations (Test Group 1); feldspathic cores (from feldspathic prefabricated CAD/CAM blocks) adhesively luted to CosmoPost zirconia posts (Test Group 2); and IPS Empress cores directly pressed to CosmoPost zirconia posts (Test Group 3). All-ceramic crowns from feldspathic ceramic were constructed using a CAD/CAM system (Cerec 3D) for all specimens. The post-core complexes were tested to failure with the load applied at 45° angled relative to the tooth long axis. The load at fracture was recorded. Results: The maximum fracture strength of the milled zirconia cores (Test Group 1) was 577 N; corresponding values for the milled feldspathic cores (Test Group 2) and the pressed cores (Test Group 3) were 586 and 585 N, respectively. Differences were not statistically significant at P < 0.05 (P = 0.669). Conclusions: All-ceramic cores adhesively luted on zirconia posts and one-piece all-ceramic zirconium post-core structures offer a viable alternative to conventional pressing.

Evaluation of Different Methods of Optical Impression Making on the Marginal Gap of Onlays Created with CEREC 3D

Clinical Relevance The marginal gap of ceramic onlays manufactured by Cerec 3D present a similar marginal gap whether the optical impression is taken intraorally using the Cerec powder or extraorally using a stone model.

Possible errors during the optical impression procedure

Introduction. Modern technologies offer a range of benefits and significantly improve specific therapeutic procedures in dentistry. However, despite gaining experience and training there are still some mistakes in their implementation. The aim of this study was to describe the most common errors during intraoral scanning, 'optical impression' procedure, during CAD-CAM technology for production of dental restorations. Material and Methods. Cerec? 3D CAD-CAM system for one visit tooth reconstruction by inlays, onlays, endocrowns, half and complete crowns and veneers from the ceramic material was used in the study. Results. Analysis included 1564 reconstruction during 5 years. The most common causes of errors performing optical impression were the result of: improper preparation of teeth, the instability of the scanner in the mouth of the patient, incorrect position and angle of the scanner to the object scanning, contrast spray applied in uneven layer, the presence of fluid in the region scan, the presence of artifacts in the region gingival sulcus. Conclusion. Optical impression is faster procedure than conventional impression, but technologically sensitive. The most frequent errors are: improper handling of the scanner, inadequate tooth preparation, irregular powder application on the tooth and irregular use in the gingival sulcus.

Accuracy of optical scanning methods of the Cerec®3D system in the process of making ceramic inlays

Background/Aim. One of the results of many years of Cerec? 3D CAD/CAM system technological development is implementation of one intraoral and two extraoral optical scanning methods which, depending on the current indications, are applied in making fixed restorations. The aim of this study was to determine the degree of precision of optical scanning methods by the use of the Cerec?3D CAD/CAM system in the process of making ceramic inlays. Methods. The study was conducted in three experimental groups of inlays prepared using the procedure of three methods of scanning Cerec ?3D system. Ceramic inlays made by conventional methodology were the control group. The accuracy of optical scanning methods of the Cerec?3D system computer aided designcomputer aided manufacturing (CAD/CAM) was indirectly examined by measuring a marginal gap size between inlays and demarcation preparation by scanning electron microscope (SEM). Results. The results of the study showed a difference in the accuracy of the existing methods of scanning dental CAD/CAM systems. The highest level of accuracy was achieved by the extraoral optical superficial scanning technique. The value of marginal gap size inlays made with the technique of extraoral optical superficial scanning was 32.97 ? 13.17 ?. Techniques of intraoral optical superficial and extraoral point laser scanning showed a lower level of accuracy (40.29 ? 21.46 ? for inlays of intraoral optical superficial scanning and 99.67 ? 37.25 ? for inlays of extraoral point laser scanning). Conclusion. Optical scanning methods in dental CAM/CAM technologies are precise methods of digitizing the spatial models; application of extraoral optical scanning methods provides the hightest precision.

Difference Between Selected and Obtained Shade for Metal-ceramic Crown Systems

Clinical Relevance Veneered electroformed crowns and In-Ceram alumina crowns made with CEREC 3D produced shade-matching that was significantly better than that obtained with conventional porcelain-fused-to-metal crowns.