Abstract
Statement of problem
The marginal gap and ceramic bond strength of metal-ceramic restorations are important
for success. However, studies evaluating the marginal gap and ceramic bond strength
of fixed partial dentures (FPDs) produced with 3D printing technologies such as selective
laser melting (SLM) are scarce.
Purpose
The purpose of this in vitro study was to investigate the marginal gap of cobalt-chromium
(Co-Cr) alloy frameworks produced by SLM technology before and after ceramic firing.
Additionally, the metal-ceramic bond strength was evaluated with the Schwickerath
crack-initiation test according to the International Standards Organization (ISO)
9693-1:2012.
Material and methods
Conventional impressions were made, and the definitive cast of a patient requiring
a 4-unit FPD was scanned. After designing the FPD, the files were sent to a service
center for the fabrication of a metal master model, 80 Co-Cr frameworks, and 80 flat
specimens (25×3×0.5 mm) with SLM technology. The marginal gap between frameworks and
the abutment tooth of the metal master model was nondestructively measured by using
an optical coordinate-measuring machine. A total of 80 sets, consisting of 1 framework
and 1 flat specimen, were sent to 80 dental laboratory technicians for ceramic firing.
Detailed instructions for correct manipulation of the framework and flat specimen
were provided. The marginal gap was remeasured, and the 3-point bend test was used
to evaluate metal-ceramic bond strength.
Results
Only 28 of the 80 dental technicians returned the specimens within a prespecified
time and/or in adequate condition. The mean ±standard deviation marginal gap of the
framework before ceramic firing was 25 ±9 μm and 34 ±12 μm after firing. The difference
was statistically significant (P=.001). The mean ±standard deviation 3-point bend strength was 33 ±9 MPa.
Conclusions
Ceramic firing affected the marginal gap; however, all Co-Cr frameworks had a marginal
gap lower than 120 μm, which is reported to be a clinically acceptable limit. Most
of the specimens (80%) had a metal-ceramic bond strength value higher than the 25-MPa
ISO 9693 requirement. Five of 28 dental laboratory technicians were not able to comply
with ceramic firing instructions.
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Article info
Publication history
Published online: November 12, 2019
Identification
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© 2019 by the Editorial Council for The Journal of Prosthetic Dentistry.
