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).
Results:
- 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.
Reference:
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.
https://doi.org/10.1016/j.jdent.2022.104181
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