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


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.
Bonfante
Estevam Augusto
EA
Department of Prosthodontics, Integrated Center for Research, University of São Paulo, Bauru, SP, Brazil. estevamab@gmail.com
Coelho
Paulo Guilherme
PG
Navarro
Jose Manuel
JM
Pegoraro
Luiz Fernando
LF
Bonfante
Gerson
G
Thompson
Van Purdy
VP
Silva
Nelson Renato Franç Alves
NR
D000044:Dental Abutments; D003722:Dental Alloys; D015921:Dental Implants; D003776:Dental Porcelain; D019094:Dental Prosthesis, Implant-Supported / Q000295:instrumentation*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D006801:Humans; D015203:Reproducibility of Results; D015040:Zirconium
D003722:Dental Alloys; D015921:Dental Implants; C051993:palladium-silver alloy W1; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide