Influence of scanner, powder application, and adjustments on CAD-CAM crown misfit
Available online 8 July 2017
Abstract
Statement of problem
The
manufacturers of computer-aided design and computer-aided manufacturing
(CAD-CAM) systems emphasize that new technologies can improve the
marginal fit of dental crowns. However, data supporting this claim are
limited.
Purpose
The
purpose of this in vitro study was to investigate the differences among
the following fabrication methods on the marginal discrepancy of dental
crowns: intraoral optical scanners, powder application, and adjustments
of intaglio surface.
Material and methods
A
single human premolar was fixed on a typodont and prepared to receive
crowns prepared by the CEREC CAD-CAM system. Three fabrication
techniques were used: digital impressions using the CEREC Bluecam
scanner with titanium dioxide powder (TDP), digital impressions using
the CEREC Omnicam scanner without TDP, and digital impressions using the
Omnicam scanner with TDP. Five experimental groups (n=10) were
designated: Bluecam (group B), Bluecam with adjustments (group BA),
Omnicam (group O), Omnicam with adjustments (group OA), and Omnicam with
TDP (group OP). The specimens were scanned using microcomputed
tomography to measure the vertical, horizontal, and internal fit and
volumetric 3-dimensional (3D) internal fit values of each luting space.
The paired t test was used to evaluate mean marginal fit change
after adjustments within the same group. One-way analysis of variance
and post hoc tests were used to compare groups B, O, and OP (α=.05).
Results
Mean
vertical fit values ±standard deviations of group B=29.5 ±13.2 μm;
BA=26.9 ±7.7 μm; O=149.4 ±64.4 μm; OA=49.4 ±12.7 μm; and OP=33.0 ±8.3
μm. Adjustments in the intaglio surface and TDP application
statistically influenced the vertical fit of group O (P<.001).
The percentage of vertical fit values <75 102.5="" 77.5="" 85.8="" 91.4="" and="" b="" ba="" different="" em="" fit="" for="" from="" group="" groups="" horizontal="" in="" m="" mean="" o="" oa="" of="" op.="" op="92.0%." other="" results="" significantly="" test="" the="" those="" values="" were="">P
<.05). The percentages of horizontal
misfit were 61.2% in group B; 73.5% in group BA; 88.1% in group O; 92.4%
in group OA; and 85.0% in group OP. Volumetric 3D internal fit values
in group B were 9.4 ±1.3 mm3; 10.7 ±1.0 mm3 in group BA; 11.8 ±2.1 mm3 in group O; 11.0 ±1.3 mm3 in group OA; and 9.6 ±0.9 mm3
in group OP. The overall results from groups B and OP were better than
those of group O, with regard to vertical misfit and volumetric 3D
internal fit.
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