Reliability and failure modes of implant-supported Y-TZP and MCR three-unit bridges

Estevam Augusto Bonfante, Paulo Guilherme Coelho, Jose Manuel Navarro, Luiz Fernando Pegoraro, Gerson Bonfante, Van Purdy Thompson, Nelson Renato Franç Alves Silva

Research output: Contribution to journalArticlepeer-review


Purpose: Chipping within veneering porcelain has resulted in high clinical failure rates for implant-supported zirconia (yttria-tetragonal zirconia polycrystals [Y-TZP]) bridges. This study evaluated the reliability and failure modes of mouth-motion step-stress fatigued implant-supported Y-TZP versus palladium-silver alloy (PdAg) three-unit bridges. Materials and Methods: Implant-abutment replicas were embedded in polymethylmethacrylate resin. Y-TZP and PdAg frameworks, of similar design (n = 21 each), were fabricated, veneered, cemented (n = 3 each), and Hertzian contact-tested to obtain ultimate failure load. In each framework group, 18 specimens were distributed across three step-stress profiles and mouth-motion cyclically loaded according to the profile on the lingual slope of the buccal cusp of the pontic. Results: PdAg failures included competing flexural cracking at abutment and/or connector area and chipping, whereas Y-TZP presented predominantly cohesive failure within veneering porcelain. Including all failure modes, the reliability (two-sided at 90% confidence intervals) for a " mission" of 50,000 and 100,000 cycles at 300 N load was determined (Alta Pro, Reliasoft, Tucson, AZ, USA). No difference in reliability was observed between groups for a mission of 50,000. Reliability remained unchanged for a mission of 100,000 for PdAg, but significantly decreased for Y-TZP. Conclusions: Higher reliability was found for PdAg for a mission of 100,000 cycles at 300 N. Failure modes differed between materials.

Original languageEnglish (US)
Pages (from-to)235-243
Number of pages9
JournalClinical Implant Dentistry and Related Research
Issue number3
StatePublished - Sep 2010


  • All-ceramic
  • Fixed partial denture
  • Mechanical testing
  • Metal ceramic restoration
  • Step-stress fatigue
  • Y-TZP

ASJC Scopus subject areas

  • Oral Surgery
  • General Dentistry


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