Conventional and modified veneered zirconia vs. metalloceramic: Fatigue and finite element analysis

Nelson R F A Silva, Estevam Bonfante, Brian T Rafferty, Ricardo A Zavanelli, Leandro L Martins, E Dianne Rekow, Van P Thompson, Paulo G Coelho

Research output: Contribution to journalArticlepeer-review

Abstract

PURPOSE: The purpose of this study was to test the hypothesis that all-ceramic crown core-veneer system reliability is improved by modifying the core design and as a result is comparable in reliability to metal-ceramic retainers (MCR). Finite element analysis (FEA) was performed to verify maximum principal stress distribution in the systems.

MATERIALS AND METHODS: A first lower molar full crown preparation was modeled by reducing the height of proximal walls by 1.5 mm and occlusal surface by 2.0 mm. The CAD-based preparation was replicated and positioned in a dental articulator for specimen fabrication. Conventional (0.5 mm uniform thickness) and modified (2.5 mm height, 1 mm thickness at the lingual extending to proximals) zirconia (Y-TZP) core designs were produced with 1.5 mm veneer porcelain. MCR controls were fabricated following conventional design. All crowns were resin cemented to 30-day aged composite dies, aged 14 days in water and either single-loaded to failure or step-stress fatigue tested. The loads were positioned either on the mesiobuccal or mesiolingual cusp (n = 21 for each ceramic system and cusp). Probability Weibull and use level probability curves were calculated. Crack evolution was followed, and postmortem specimens were analyzed and compared to clinical failures.

RESULTS: Compared to conventional and MCRs, increased levels of stress were observed in the core region for the modified Y-TZP core design. The reliability was higher in the Y-TZP-lingual-modified group at 100,000 cycles and 200 N, but not significantly different from the MCR-mesiolingual group. The MCR-distobuccal group showed the highest reliability. Fracture modes for Y-TZP groups were veneer chipping not exposing the core for the conventional design groups, and exposing the veneer-core interface for the modified group. MCR fractures were mostly chipping combined with metal coping exposure.

CONCLUSIONS: FEA showed higher levels of stress for both Y-TZP core designs and veneer layers compared to MCR. Core design modification resulted in fatigue reliability response of Y-TZP comparable to MCR at 100,000 cycles and 200 N. Fracture modes observed matched with clinical scenarios.

Original languageEnglish (US)
Article numberdoi: 10.1111/j.1532-849X.2012.00861.x
Pages (from-to)433-9
Number of pages7
JournalJournal of Prosthodontics
Volume21
Issue number6
DOIs
StatePublished - Aug 2012

Keywords

  • Computer Simulation
  • Computer-Aided Design
  • Crowns
  • Dental Porcelain
  • Dental Prosthesis Design
  • Dental Stress Analysis
  • Dental Veneers
  • Finite Element Analysis
  • Humans
  • Metal Ceramic Alloys
  • Survival Analysis
  • Yttrium
  • Zirconium

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