Influence of CAD/CAM on the fit accuracy of implant-supported zirconia and cobalt-chromium fixed dental prostheses
Volume 113, Issue 1, January 2015, Pages 22–28
Abstract
Statement of problem
Relatively
little information is available on the accuracy of the abutment-implant
interface in computer-aided design and computer-aided manufacturing
(CAD/CAM)-fabricated zirconia and cobalt-chromium frameworks.
Purpose
The
purpose of this study was to compare the fit accuracy of
CAD/CAM-fabricated zirconia and cobalt-chromium frameworks and
conventionally fabricated cobalt-chromium frameworks.
Material and methods
Four
groups of 3-unit, implant-supported, screw-retained frameworks were
fabricated to fit an in vitro model with 3 implants. Eight frameworks
were fabricated with the CAD/CAM system: 4 in zirconia and 4 in
cobalt-chromium. Another 8 were cast in cobalt-chromium with
conventional casting, including 4 with premachined abutments and 4 with
castable abutments. The vertical misfit at the implant-framework
interface was measured with scanning electron microscopy when only 1
screw was tightened and when all screws were tightened. Data were
analyzed with the Kruskal-Wallis and Mann-Whitney tests (α=.05).
Results
The
mean vertical misfit values when all screws were tightened was 5.9 ±3.6
μm for CAD/CAM-fabricated zirconia, 1.2 ±2.2 μm for CAD/CAM-fabricated
cobalt-chromium frameworks, 11.8 ±9.8 μm for conventionally fabricated
cobalt-chromium frameworks with premachined abutments, and 12.9 ±11.0 μm
for the conventionally fabricated frameworks with castable abutments;
the Mann-Whitney test found significant differences (P<.05) among all frameworks, except between the conventionally fabricated frameworks (P=.619). No significant differences were found among the groups for passive fit gap measurements (P>.05).
Conclusions
When
all of the screws were tightened, the CAD/CAM frameworks exhibited
better fit accuracy compared with the conventionally fabricated
frameworks. High levels of passive fit were achieved for the evaluated
techniques.
- Supported by Neodent and Laboratory LTN.
Comments