International Journal of Computerized Dentistry, 01/2016

Zirconia crowns combine the advantages of metal restorations, such as minimally invasive tooth preparation and ease of cementation, with those of full ceramic crowns, such as low thermal conductivity and tooth color. With the introduction of a high-speed sintering procedure, it is possible to produce and cement zirconia crowns and small monolithic bridges in a Cerec Single Visit procedure. This new procedure is compared to established chairside methods. Keywords: zirconia, SpeedFire furnace, high-speed sintering, Cerec crowns, Cerec zirconia

Objectives: The accuracy of computer-aided design/computer- aided manufacturing (CAD/CAM) systems is linked to their technical characteristics and reliability for manufacturing the restoration designed. The aim of this study was to compare the accuracy of fit of zirconia copings manufactured with different CAD/CAM systems and their capacity to conform to pre-established spacer design settings. Methods: Sixty zirconia copings were manufactured by three CAD/CAM systems, with their spacers set as recommended by their manufacturer on occlusal, axial, and marginal surfaces. The 3D triple-scan optical technique was used to obtain a fit mapping and to analyze the marginal and axial accuracy of fit. The reliability of the 3D measurement method was estimated using intraclass correlation and repeatability coefficients. The preparation coping interface width results were statistically analyzed using non-parametric analysis (Kruskal-Wallis, one-way ANOVA, and Wilcoxon signedrank tests) (P < 0.05). Results: The repeatability coefficient was 6, 8, and 15 μm for axial, marginal, and occlusal interface width measurements, respectively. For the three systems tested, no differences were found in the marginal area of the copings studied, with a mean fitting accuracy ranging from 54.3 to 66.6 μm interface width. Statistically significant differences between groups were observed for the fitting accuracy measured in axial and occlusal areas. With the spacers set in the different areas, mean fit measurements of the zirconia copings were significantly larger, with an increased fit width ranging from 30 to 73 μm. Significance: The three CAD/CAM systems evaluated allowed similar marginal accuracy but failed to reproduce the pre-established spacer parameters, with larger spacing showing throughout. Keywords: 3D accuracy of evaluation, accuracy of fit, CAD/CAM, dental prostheses, design parameters

The dental milling machine is an important device in the dental CAD/CAM chain. Nowadays, dental numerical controlled (NC) milling machines are available for dental surgeries (chairside solution). This article provides a mechanical engineering approach to NC milling machines to help dentists understand the involvement of technology in digital dentistry practice. First, some technical concepts and definitions associated with NC milling machines are described from a mechanical engineering viewpoint. The technical and economic criteria of four chairside dental NC milling machines that are available on the market are then described. The technical criteria are focused on the capacities of the embedded technologies of these milling machines to mill both prosthetic materials and types of shape restorations. The economic criteria are focused on investment costs and interoperability with third-party software. The clinical relevance of the technology is assessed in terms of the accuracy and integrity of the restoration. Keywords: dental milling, CAD/CAM, surface integrity, Cerec, Lyra, E4D, Carestream, Planmeca

Aim: To investigate whether the fully digital, plasterless fabrication of clinically usable Michigan splints can be accomplished in a time- and cost-efficient manner. Materials and methods: Digital scans of the maxillary and mandibular arches of 10 subjects were acquired with an intraoral scanner (3Shape, Copenhagen) and used to generate virtual models of the dental arches. Jaw relation records were made using jigs placed on the subjects' anterior teeth, and silicone registration material was referenced to the jaw models. The data sets were then sent via the company's online portal to the dental laboratory, where computer-aided design (CAD) of the Michigan-type maxillary splints was performed. After receiving the designs, the splints were milled in-office using computer-aided manufacturing (CAM) software, and finished manually. During try-in, the splints where checked for fit, retention quality, and occlusal contacts of the mandibular teeth on the splint surfaces in static and dynamic occlusion. Results: Fit and retention were clinically acceptable in 10 splints and 9 splints, respectively. The number of initial occlusal contacts on the splint surfaces ranged from 4 to 16. Conclusions: The question addressed in this study can be answered in the affirmative. Some of the main advantages of digital manufacturing of Michigan splints over traditional, conventional, impression-based manufacturing are the time-efficient manufacturing process, the high material quality, and the possibility of manufacturing duplicate splints. Keywords: workflow, digital impression, intraoral scanning, computer-aided design, computer-aided manufacturing, jaw relation record, occlusal splints, craniomandibular disorders, bruxism

The advent of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in dentistry has enabled a wide range of applications. The Cerec Acquisition Center (Cerec AC, Sirona Dental Systems Inc., Charlotte, NC) allows for the construction of all-porcelain restorations, either in-office or through a remote dental laboratory. One feature of the Cerec AC is its ability to duplicate the dental morphology of an existing tooth onto a new CAD/CAM ceramic restoration designed for that tooth. This design mode capability of the Cerec AC is termed Biogeneric Copy. This function has been discussed in the literature where it has been utilized to fabricate a CAD/CAM ceramic crown to fit an existing removable partial denture (RPD).1-3 There are occasions in dentistry where the exact anatomy and position of an existing tooth, not associated with an RPD, should ideally be replicated in a definitive restoration. This case report describes such an occasion. Keywords: Biogeneric Copy, Cerec, CAD/CAM