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J M van der Zel

Publications and source records attributed to J M van der Zel.

7 recordsLinked to original sources
PubMed2001

The CICERO system for CAD/CAM fabrication of full-ceramic crowns.

The CICERO method of crown fabrication consists of optically digitizing a gypsum die, designing the crown layer buildup, and subsequently pressing, sintering, and milling consecutive layers of a shaded high-strength alumina-based core material, a layer of dentin porcelain, and a final layer of incisal porcelain. Final finishing is performed in the dental laboratory. The CICERO method allows efficient production of all-ceramic restorations without compromising esthetics or function. This article reviews the process involved in the fabrication of a CICERO crown.

Aluminum Oxide↗
PubMed1999

[CAD/CAM-copings for partial coverage].

Aim of the study was to evaluate the Computer Integrated Ceramic Reconstruction (CICERO)-system and the Ceramic Reconstruction (CEREC)-system for the production of all ceramic copings for partial coverage. Posterior teeth were prepared and the stone dies were made. Accuracy analyses were performed on ceramic restorations made by means of the CICERO and by means of the CEREC technique. The marginal gaps were compared to that of a control cast metal restoration. The results demonstrate that the marginal gaps of the CICERO and CEREC copings varied respectively for the premolar 58-80 microns (mean 69 microns) and 71-91 microns (mean 81 microns). For the upper molar 63-92 microns (mean 78 microns) and 68-110 microns (mean 89 microns) and for the lower molar 54-98 microns (mean 76 microns) and 73-99 microns (mean 86 microns). Control cast metal partial coverage restorations showed marginal gaps of 33, 49 and 41 microns. It is concluded that computers can produce copings for partial coverage preparations on stone dies with a mean marginal gap for CICERO copings of 74 microns and for CEREC copings of 85 microns. These values were obtained before optimizing the marginal fit by means of porcelain veneering.

Ceramics↗
PubMed1988

Carbon absorption of palladium-enriched ceramic alloys.

Palladium-enriched alloys are sensitive to carbon absorption. High carbon levels in ceramic alloys negatively influence some mechanical properties and cause porosities in the porcelain during the firing process. The influence of the palladium content on carbon absorption of alloys with a range of palladium content from 5 to 80% approximately was investigated. Carbon content was measured for alloys in the 'as received' condition as well as after melting once and three times. Carbon contents up to 200 ppm were measured in the case of a high-palladium system.

Absorption↗
PubMedDate not supplied

Measurement of the margins of partial-coverage tooth preparations for CAD/CAM.

PURPOSE: This study tested the hypothesis that a scanning laser 3-dimensional digitizer is a precise and accurate instrument to measure chamfered and beveled margins of partial coverage tooth preparations for computer-aided design/computer-aided manufacturing (CAD/CAM). MATERIALS AND METHODS: The margins were measured by the digitizer on stone dies and calculated by triangulation into a 3-D representation. Instrument precision was defined as the ability to reproduce the same margin in repeated measurements and expressed as the coefficient of variation as a percentage. Instrument accuracy for chamfered and beveled margins was estimated by correlating their measurements to the measurement of the margin of a spherical calibration "phantom" with known dimensions. Accuracy was expressed as the standard deviation. RESULTS: The precision errors for the box- and cusp-chamfered margins and cusp-beveled margins were 3.9%, 3.4%, and 2.4%, respectively. With regard to accuracy the standard deviations of the measurements of the box- and cusp-chamfered margins and cusp-beveled margins were 19 microns, 21 microns, and 24 microns, respectively, compared to 15 microns for the phantom. CONCLUSION: Measurements of chamfered and beveled margins by a scanning laser 3-D digitizer for CAD/CAM are (1) precise (error < 4%) and (2) accurate, with a standard deviation of less than 9 microns compared to optimal measurements of the spherical margin of the phantom.

Analog-Digital Conversion↗