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.
Department of Prosthodontics, Integrated Center for Research, University of São Paulo, Bauru, SP, Brazil. estevamab@gmail.com
Estevam Augusto
EA
Bonfante
Paulo Guilherme
PG
Coelho
Jose Manuel
JM
Navarro
Luiz Fernando
LF
Pegoraro
Gerson
G
Bonfante
Van Purdy
VP
Thompson
Nelson Renato Franç Alves
NR
Silva
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