The occlusal precision of laboratory versus CAD/CAM processed all-ceramic crowns.
OBJECTIVE
The null hypothesis was tested: There is no difference between two all-ceramic crown systems, the Cerec method (CHAIR) and the IPS Empress method (LAB), with respect to occlusal precision and time expenditure for the dentist.


METHODS
20 casts representing clinical situations were mounted in semi-adjustable articulators to serve as simulation models. The left lower first molars were prepared to receive feldspathic ceramic crowns. The minimum number of three (Min3) occlusal contacts and their desired location was defined on each crown before preparation. Two crowns were produced on each die: (CHAIR) was applied in order to simulate a chair-side treatment and [LAB] was applied to simulate the laboratory/clinical mode of production. Additionally the time required to perform the occlusal adjustment was measured. For occlusal analysis, the (Min3) were divided by the contacts that were "actually achieved" (ACT). Mean quotients for (LAB) and (CHAIR) were calculated (n = 20 each). The Wilcoxon signed rank test at P < or = 0.05 was applied to determine statistical significance.


RESULTS
The mean quotients MEAN QU (Min3)/(ACT) of 0.87 for (CHAIR) and 0.94 for (LAB) and the time expenditure for simulating intraoral occlusal adjustment of 3.44 minutes for (CHAIR) and 3.79 minutes for (LAB) did not differ significantly.
Reich
Sven
S
Department of Prosthodontics and Dental Materials, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074 Aachen, Germany. sreich@ukaachen.de
Brungsberg
Beate
B
Teschner
Hubertus
H
Frankenberger
Roland
R
D017076:Computer-Aided Design; D003442:Crowns; D003766:Dental Occlusion; D003776:Dental Porcelain; D017267:Dental Prosthesis Design / Q000379:methods*; D006801:Humans; D007574:Jaw Relation Record; D003765:Models, Dental; D008963:Molar; D019558:Occlusal Adjustment; D018709:Statistics, Nonparametric; D013997:Time Factors
D003776:Dental Porcelain