Statement of problem
Computer-aided design and computer-aided manufacturing (CAD/CAM) generated restorations
are gaining popularity. However, limited clinical evidence is available for single-unit
posterior CAD/CAM restorations fabricated with established and newer crown materials.
Purpose
The purpose of this clinical study was to assess the restoration quality of and gingival
response to CAD/CAM fabricated posterior single-tooth restorations with different
processing technologies.
Material and methods
Twenty-two individuals in need of posterior complete coverage crowns were recruited
under an institutional review board approved protocol. Teeth were randomized to 1
of 3 groups: metal ceramic, lithium disilicate, and monolithic zirconia. An unprepared
or minimally restored tooth on the contralateral side was chosen as a control tooth
for gingival measurements with each participant. Teeth were prepared and scanned intraorally
by 1 of 3 experienced practitioners. A total of 32 restorations were digitally designed
and fabricated with either milling technology or rapid-prototype printing and casting
with conventional porcelain application. Restorations were evaluated with modified
United States Public Health Service criteria for contour, marginal adaptation, occlusion,
and shade. Gingival crevicular fluid volume and bleeding on probing were recorded
preoperatively, at 1-month and 6-month postcementation visits. Polyvinyl siloxane
impressions were made of the buccal margin of cemented restorations and evaluated
with microcomputed tomography to assess marginal adaptation (horizontal discrepancy).
The Mantel Haenszel row mean score was used to assess whether the crown systems differed
with respect to the modified United States Public Health Service criteria. Linear
mixed models were used to assess whether the average gingival volumes were affected
by the explanatory variables (crown system, tooth status [treated vs control], or
visit). A generalized estimating equation approach was used to assess whether bleeding on
probing was affected by the explanatory variables. One-way ANOVA was used to assess
marginal discrepancy values among the crown systems (α=.05 for all tests).
Results
Twelve metal ceramic, 10 lithium disilicate, and 10 zirconia restorations were fabricated
for 22 participants. Zirconia restorations were significantly different from the other
2 crown systems (P<.001) with respect to occlusion. No occlusal adjustment was needed on 80% of the
zirconia restorations. The average gingival crevicular fluid volumes did not differ
among crown systems, between treated and control groups, or over time. The average
horizontal marginal discrepancy was significantly different between lithium disilicate
and zirconia crowns (P=.027), with zirconia crowns having the least amount of horizontal marginal discrepancy.
Conclusions
Given the small sample size and limitations of this study, CAD/CAM-generated restorations
for posterior teeth made from different materials had acceptable clinical results.
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Article info
Publication history
Published online: June 28, 2014
Footnotes
This study was supported by an American Academy of Fixed Prosthodontics Stanley D. Tylman grant.
Identification
Copyright
© 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
