3D printing with press technique improves fatigue survival of LD crowns

Lithium disilicate monolithic crowns have similar fatigue
behaviour in CAD/CAM versus 3D-printing/pressed techniques according to a recent
study published in the Journal of Dentistry.

This study aimed to evaluate the adaptation and fatigue
behaviour of lithium disilicate glass-ceramic (LD) monolithic crowns produced by the press (combined with 3D-printing) and CAD/CAM milling (control) techniques.

Thirty abutment preparations with a chamfer finish line were
produced with a dentin analogue material and scanned with an extraoral scanner.
Captured images were processed using CAD software to design a premolar. Blocks
of LD were milled using a CAD/CAM system. For the press technique, crowns were
first 3D-printed using polymeric material and the heat-pressing protocol was
performed. Crowns were adhesively cemented to the abutments and scanned using
micro-CT. Files were processed and cross-sectional images were analysed in five
measuring points marginal, axial angle, axial, occlusal angle and occlusal.
Fatigue test was performed in an MTS universal testing machine (2 Hz, 37°C
distilled water) using an anatomic composite piston, following the step-stress
method. Failures were detected with an acoustic system and confirmed by
transillumination. A cumulative damage-Weibull distribution (95% CI) was used
to analyze the fatigue data. Gap thickness data were analyzed using
Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05).


CAD/CAM milling resulted in larger gap thickness
in the occlusal area and smaller gap thickness in the axial angle and axial
area than press (p<0.05). The probability of failure was similar for
crowns produced with CAD/CAM milling and press. The most frequent failure mode
was radial crack.

LD crowns produced using the combination of
3D-printing/press technique showed similar fatigue behaviour to CAD/CAM milled
control group and resulted in smaller gap thickness at the occlusal region. A
more controlled process can be achieved by replacing conventional restoration
waxing with 3D printing, which in combination with the press technique produces
lithium disilicate glass-ceramic monolithic crowns with good adaptation and
high fatigue survival.


CAD/CAM versus 3D-printing/pressed lithium disilicate
monolithic crowns: adaptation and fatigue behaviour by Rodrigo Ottoni et al.
published in the Journal of Dentistry.


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