Abstract
Objectives: This study compared the reliability and fracture patterns of zirconia cores veneered with pressable porcelain submitted to either axial or off-axis sliding contact fatigue. Methods: Forty-two Y-TZP plates (12 mm × 12 mm × 0.5 mm) veneered with pressable porcelain (12 mm × 12 mm × 1.2 mm) and adhesively luted to water aged composite resin blocks (12 mm × 12 mm × 4 mm) were stored in water at least 7 days prior to testing. Profiles for step-stress fatigue (ratio 3:2:1) were determined from single load to fracture tests (n = 3). Fatigue loading was delivered on specimen either on axial (n = 18) or off-axis 30° angulation (n = 18) to simulate posterior tooth cusp inclination creating a 0.7 mm slide. Single load and fatigue tests utilized a 6.25 mm diameter WC indenter. Specimens were inspected by means of polarized-light microscope and SEM. Use level probability Weibull curves were plotted with 2-sided 90% confidence bounds (CB) and reliability for missions of 50,000 cycles at 200 N (90% CB) were calculated. Results: The calculated Weibull Beta was 3.34 and 2.47 for axial and off-axis groups, respectively, indicating that fatigue accelerated failure in both loading modes. The reliability data for a mission of 50,000 cycles at 200 N load with 90% CB indicates no difference between loading groups. Deep penetrating cone cracks reaching the core-veneer interface were observed in both groups. Partial cones due to the sliding component were observed along with the cone cracking for the off-axis group. No Y-TZP core fractures were observed. Conclusions: Reliability was not significantly different between axial and off-axis mouth-motion fatigued pressed over Y-TZP cores, but incorporation of sliding resulted in more aggressive damage on the veneer.
Original language | English (US) |
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Pages (from-to) | 318-324 |
Number of pages | 7 |
Journal | Journal of Dentistry |
Volume | 38 |
Issue number | 4 |
DOIs | |
State | Published - Apr 2010 |
Keywords
- All-ceramics
- Pressable porcelain
- Reliability
- Step-stress fatigue
- Y-TZP
- Zirconia
ASJC Scopus subject areas
- General Dentistry