Reliability of Implant-supported Zirconia Three-Unit Fixed-Partial-Dentures using different veneering Porcelains

Objectives: To investigate mouth-motion step-stress fatigue of zirconium oxide three-unit fixed-partial-dentures(FPDs) using two different veneering porcelains, a traditional hand build-up porcelain(Sintered) and a pressed ceramic(Over-pressed). Methods: 28 standardized Procera-AllZircon-FPDs-frameworks*(ZrO2-framework) were CAD/CAM fabricated. Frameworks were veneered with sintered porcelain NobelRondo*(n=14) or over-pressed with NobelRondo-Press*(n=14). All FPDs were cemented (Ketac Cem, 3M-ESPE) to individualized zirconia-abutments* based on Replace-straight-Groovy* implants (premolar: RP-4x13mm; molar: WP-5x13mm) (*NobelBiocare). Specimens were incubated in water at 37°C for at least 14-days. A Step-Stress Accelerated Life Test (SSALT) with three stress-time-varying profiles was performed based on preliminary load to failure data. Failure was defined by delamination or chipping. Specimens were inspected (polarized-specular-reflection-light-microscopy) at regular intervals to visualize crack propagation and failure mode. Reliability software (Alta Pro, Reliasoft) was employed. Results: Off-axis single-load-testing at the buccal cusp pontic area demonstrated porcelain chipping (~1300N) followed by core fracture (~1900N). Inner cone/ median radial crack propagation were observed in the veneer during fatigue resulting in partial veneer chipping. Weibull-stress-level-probability-curves were calculated and the reliability (2-sided at 90.0 % confidence bounds) for 50K cycles and a 400N load indicated values of 0.97(0.99/0.77) for Sintered-FPDs and 0.71(0.86/0.45) for Over-pressed-FPDs. Conclusions: Based on current data implant-supported all zirconium oxide FPDs demonstrated robust fatigue resistance. Sintered was not statistically more reliable than Pressed but had fewer low load low cycle failures which may be of clinically important. Supported by Nobel Biocare, Goteborg, Sweden.

christian.stappert@nyu.edu.