Purpose/Aim: Fatigue resistance is a crucial factor for the clinical long-term survival of prosthetic restorations. High strength full-contour ceramics combined with CAD/CAM technology showed promising clinical outcomes and lower costs; however, their fatigue resistance was seldom compared to natural teeth. Aim of this study was to validate a fatigue testing machine concept comparing the fatigue survival and the wear patterns of monolithic ceramic crowns to those of sound human teeth. The null hypothesis was that the fatigue resistance and the wear pattern induced by the machine did not differ among the tested groups (alpha=.05) Materials and Methods: Five groups (n=20) of monolithic crowns of different thickness (1.0mm Y-TZP HT, 1.0mm cubic-zirconia UT, 1.5mm cubic-ziconia UT, 1.0mm cubic-zirconia ST, all from Kuraray-Noritake, and 1.5mm lithium-disilicate, L-DIS, from Ivoclar Vivadent) and 20 human sound third molars have been collected and mounted in epoxy-resin cylinders, then subjected to impact fatigue cycles (Ball-Mill). The specimens were analyzed after 10, 20, 30 and 60min cycling, then analyzed every hour until a total time of 480min cycling. Wear and damage analysis was carried out using a stereomicroscope. The material losses (mm3) were calculated (Rhinoceros software) by comparing the digital impressions (Carestream CS3500 scanner) of each specimen at the different time intervals. Gehan-Breslow-Wilcoxon test and Kruskal-Wallis with post-hoc Dunn's test were applied to survival and volume loss data (alpha=.05). Results: After 480min 1.0mm Y-TZP HT showed the highest fatigue resistance, similar (p>0.05) to 1.5mm UT cubic-zirconia and 1.5mm L-DIS. 1.0mm UT cubic-zirconia showed the highest failure rate (p<0.001). At 60min fatigue cycling, natural teeth showed significantly higher volume loss (mean 59.92mm3, p<0.05) than all ceramic crown groups, that ranged from <0.01mm3 (1.0mm Y-TZP HT) to 18mm3 (1.5mm L-DIS). Morphological characterization of natural teeth showed neatly exposed dentin after 60min cycling. Digital and CAD analysis of tissue loss pattern occurred on natural teeth was related to clinical functional time through Miles classification of occlusal wear during life. A correspondence of 18 years of clinical function for 60min cycling for the Ball-Mill machine was suggested Conclusions: Fracture growth can be induced by Ball-Mill fatigue machine on ceramics and dental tissues causing wear patterns similar to those clinically observed. The response to fatigue of ceramic crowns are in accordance with the literature data and with the expected behavior drawn from their different mechanical properties; thus, the results suggest that the Ball-Mill machine could be a fast and cost-effective method to foresee the clinical behavior of different all-ceramic crowns.
Fatigue testing machine design for dental ceramics: a validation study
P. Baldissara;R. Scotti;L. Ciocca
2018
Abstract
Purpose/Aim: Fatigue resistance is a crucial factor for the clinical long-term survival of prosthetic restorations. High strength full-contour ceramics combined with CAD/CAM technology showed promising clinical outcomes and lower costs; however, their fatigue resistance was seldom compared to natural teeth. Aim of this study was to validate a fatigue testing machine concept comparing the fatigue survival and the wear patterns of monolithic ceramic crowns to those of sound human teeth. The null hypothesis was that the fatigue resistance and the wear pattern induced by the machine did not differ among the tested groups (alpha=.05) Materials and Methods: Five groups (n=20) of monolithic crowns of different thickness (1.0mm Y-TZP HT, 1.0mm cubic-zirconia UT, 1.5mm cubic-ziconia UT, 1.0mm cubic-zirconia ST, all from Kuraray-Noritake, and 1.5mm lithium-disilicate, L-DIS, from Ivoclar Vivadent) and 20 human sound third molars have been collected and mounted in epoxy-resin cylinders, then subjected to impact fatigue cycles (Ball-Mill). The specimens were analyzed after 10, 20, 30 and 60min cycling, then analyzed every hour until a total time of 480min cycling. Wear and damage analysis was carried out using a stereomicroscope. The material losses (mm3) were calculated (Rhinoceros software) by comparing the digital impressions (Carestream CS3500 scanner) of each specimen at the different time intervals. Gehan-Breslow-Wilcoxon test and Kruskal-Wallis with post-hoc Dunn's test were applied to survival and volume loss data (alpha=.05). Results: After 480min 1.0mm Y-TZP HT showed the highest fatigue resistance, similar (p>0.05) to 1.5mm UT cubic-zirconia and 1.5mm L-DIS. 1.0mm UT cubic-zirconia showed the highest failure rate (p<0.001). At 60min fatigue cycling, natural teeth showed significantly higher volume loss (mean 59.92mm3, p<0.05) than all ceramic crown groups, that ranged from <0.01mm3 (1.0mm Y-TZP HT) to 18mm3 (1.5mm L-DIS). Morphological characterization of natural teeth showed neatly exposed dentin after 60min cycling. Digital and CAD analysis of tissue loss pattern occurred on natural teeth was related to clinical functional time through Miles classification of occlusal wear during life. A correspondence of 18 years of clinical function for 60min cycling for the Ball-Mill machine was suggested Conclusions: Fracture growth can be induced by Ball-Mill fatigue machine on ceramics and dental tissues causing wear patterns similar to those clinically observed. The response to fatigue of ceramic crowns are in accordance with the literature data and with the expected behavior drawn from their different mechanical properties; thus, the results suggest that the Ball-Mill machine could be a fast and cost-effective method to foresee the clinical behavior of different all-ceramic crowns.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
