Abstract
Statement of problem
To complement the digital workflow for manufacturing fixed dental prostheses, both
high-strength frameworks and esthetic veneers should be designed and fabricated digitally.
However, how the fracture load of digitally veneered restorations compares with conventionally
fabricated restorations is unclear.
Purpose
The purpose of this in vitro study was to examine the fracture load of digitally and
conventionally veneered zirconia and cobalt chromium crowns initially and after thermomechanical
aging.
Material and methods
Milled zirconia and cobalt chromium copings for a maxillary canine were fabricated
(N=96). Digital veneers were milled and connected to the copings with a sintered ceramic
slurry. The conventional veneers were fabricated by using a master mold, and the crowns
were bonded to the cobalt chromium abutments. Half the specimens were subjected to
6000 thermal (5 °C to 55 °C, 60 seconds) and 1 200 000 mechanical (50 N, 1.5 Hz, 0.7
mm lateral movement) cycles opposed by steatite antagonists, and the fracture load
was determined. Fracture types were categorized, and scanning electron microscopy
performed. The data were analyzed with a 3-way global univariate analysis of variance,
t test, the Pearson chi-squared test, and the Weibull modulus (α=.05).
Results
Unlike the framework material (P=.316) and artificial aging (P=.064), the veneering protocol affected the fracture load (P=.007). Digital veneers (range: 2242 to 2929 N) led to lower values than conventional
veneers (range: 2825 to 3166 N), which was significant for aged cobalt chromium copings
(P=.024; 2242 versus 3107 N). Conventionally veneered crowns showed lower Weibull moduli
after thermomechanical aging (range: 3.2 to 3.5) than initially (range: 7.8 to 11.4).
The copings of all the zirconia specimens fractured, while chipping occurred with
the cobalt chromium specimens.
Conclusions
The high fracture load values of the veneered crowns, even after simulated 5-year
aging, indicated sufficient mechanical properties (nearly 4-fold the average occlusal
force of 600 N) for the successful clinical application of digitally veneered zirconia
and cobalt chromium copings.
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Article info
Publication history
Published online: May 25, 2023
Publication stage
In Press Corrected ProofFootnotes
Funding: Supported by bredent.
Identification
Copyright
© 2023 by the Editorial Council for The Journal of Prosthetic Dentistry.
