Journal of Prosthetic Dentistry
Abstract
Statement of problem
Monolithic
zirconia crowns fabricated with computer-aided design and
computer-aided manufacturing (CAD-CAM) have recently become a common
practice for the restoration of posterior teeth. The marginal fit of
monolithic zirconia crowns may be affected by different cement space
parameters set in the CAD software. Information is scarce regarding the
effect of cement space on the marginal fit of monolithic zirconia crowns
fabricated with CAD-CAM technology.
Purpose
The
purpose of this in vitro study was to evaluate the effect of cement
space on the marginal fit of CAD-CAM-fabricated monolithic zirconia
crowns before cementation.
Material and methods
Fifteen
right maxillary first molar typodont teeth with standardized anatomic
preparations for complete-coverage ceramic crowns were scanned with a
3-dimensional laboratory scanner. Crowns were designed 3-dimensionally
using software and then milled from presintered monolithic zirconia
blocks in a computer numerical control dental milling machine. The
cement space was set at 25 μm around the margins for all groups, and
additional cement space starting 1 mm above the finish lines of the
teeth was set at 30 μm for group 25-30, 40 μm for group 25-40, and 50 μm
for group 25-50 in the CAD software. A total of 120 images (3 groups, 5
crowns per group, 8 sites per crown) were measured for vertical
marginal discrepancy under a stereoscopic zoom microscope and the data
were statistically analyzed with 1-way analysis of variance, followed by
the Tukey honestly significant difference test (α=.05).
Results
The
results showed that different cement space values had statistically
significant effect on the mean vertical marginal discrepancy value of
tested crowns (
P<.001). The mean marginal discrepancy was 85 μm for group 25-30, 68 μm for group 25-40, and 53 μm for group 25-50.
Conclusions
Within
the limitations of this in vitro study, it was concluded that the
cement space had a significant effect on the marginal fit of
CAD-CAM-fabricated monolithic zirconia crowns. The marginal fit improved
as the cement space decreased.
Comments