J Korean Acad Prosthodont.  2001 Jun;39(3):243-249.

Evaluation of marginal fidelity of copy-milled and CAD/CAM all ceramic crowns

• Jeong SM
• Kang DW
• Wolf C

Abstract

STATEMENT OF THE PROBLEM: The interest in all-ceramic restorations has increased as more techniques have become available. With the introduction of machinable dental ceramics and CAD/CAM systems of Copy-milling systems there is a need for evaluating the quality levels of these new fabrication techniques. PURPOSE: This study was to evaluate the fitting accuracy of machined all-ceramic crowns made out of an industrially prefabricated feldspathic porcelain. MATERIAL AND METHODS: Three master models with different cutting depth (0.8mm/1.0mm/1.2mm) were produced using a palladium-silver alloy. A total of 36 working dies, 12 of each form, was used for the modellation of prototype resin copings and 36 additional crowns, 12 of each cutting depth, were produced by using the CEREC 2 system for all crowns. The maginal fit of all 72 crowns was then evaluated on their respective master die at 54 circularly staggered points of measurement per crown under a fixation pressure of 30 N by using a computerized video image system.
RESULTS
The medians of the copy-milled CELAY crowns ranged from 29 to 36 micrometer. The highest value for the marginal gap was found in group B (cutting depth 1.0mm) at 107 micrometer. The median for the CEREC 2 crowns was found between 43.5 and 70 micrometer. The maximum values for all three groups ranged from 181 micrometer to 286 micrometer. With 286 micrometer, the highest value for marginal gap was found in group C, the Kruskal-Wallis test and multiple comparisons analysis procedure revealed a significant influence of the production technique on the marginal fit in all three groups (p<0.02).
CONCLUSION
1. The CELAY system is capable to produce all-ceramic crowns with a significantly better marginal fit than the CELAY system. 2. As far as premolar crowns produced with the CELAY system are concerned, the cutting depth has a significant influence on fitting accuracy. 3. The production of crowns with an acceptable marginal fit is possible with both systems. However, adhesive luting is recommended for milled feldspathic porcelain crowns.

MeSH Terms

Adhesives
Alloys
Bicuspid
Ceramics*
Crowns*
Dental Porcelain
Adhesives
Alloys
Ceramics
Dental Porcelain