Impact of high-speed sintering, layer thickness and artificial aging on the fracture load and two-body wear of zirconia crowns

Abstract

Objective: To investigate the impact of high-speed sintering, layer thickness and artificial aging in a chewing simulator on the fracture load (FL) and two-body wear (2BW) of 4Y-TZP crowns.

Methods: 4Y-TZP crowns (Ceramill Zolid HT+, Amann Girrbach AG) in three different layer thicknesses (0.5, 1.0, 1.5; N=192, n=64/group) were manufactured using CAD/CAM technology and sintered at 1580°C (high-speed sintering) or 1450°C (control group). Specimens were polished in two-steps and bonded to standardized CoCr abutments with Multilink Automix (Ivoclar Vivadent). 2BW after 6000 thermo- and 1,200,000 chewing-cycles employing enamel antagonists was determined using best fit machining. FL was tested before and after artificial aging. Univariate ANOVAs, post hoc Scheffé, unpaired t-, Kruskal-Wallis- and Mann-Whitney-U-test were computed (p<0.05).

Results: High-speed sintering resulted in less 2BW of the zirconia than the control group (p=0.013). High-speed sintering (p=0.001-0.006) and an increase in layer thickness (p<0.001-0.012) resulted in higher FL values, while artificial aging led to a reduction of FL (p<0.001).

Significance: As high-speed sintering resulted in less two-body wear of the zirconia and comparable or even higher fracture load results than the control group, this cost- and time efficient alternative presents promising mechanical results.

Keywords: Fracture load; High-speed sintering; Layer thickness; Two-body wear; Zirconia.