title: Reliability and failure modes of anterior single-unit implant-supported restorations.
abstract: OBJECTIVE
  Failures of implant-abutment connections have been observed clinically, especially in single-tooth replacements. This study sought to evaluate the reliability and failure modes of implant-supported anterior crowns restored with different implant systems.
  
  
  METHODS
  Forty-two Ti-6Al-4V dental implants (~4 mm diameter) were used for single anterior crown replacement and divided into two groups according to tested system: (NB) Replace Select system, Nobel Biocare (n = 21); and (IL) Internal connection system, Intra-Lock International (n = 21). Proprietary abutments were screwed to the implants and anatomically correct maxillary central incisor metal crowns were cemented and subjected to step-stress-accelerated life testing in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N (95% 2-sided confidence intervals) were calculated. Polarized-light and scanning electron microscopes were used for failure analyses.
  
  
  RESULTS
  The Beta values for NB and IL (2.09 and 2.05, respectively) indicated that fatigue accelerated the failure of both groups. The calculated reliability for the NB system (0.81) was lower than for the IL system (0.96), but no significant difference was observed between groups. Screw and abutment fracture was the chief failure mode in group NB, while screw fracture was most representative in specimens of group IL.
  
  
  CONCLUSIONS
  Reliability of implant-supported maxillary central incisor crowns was not significantly different between NB and IL abutments. Failure modes differed between implant systems.
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.
authors.forename: Amilcar C
authors.initials: AC
authors.lastname: Freitas
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.forename: Leandro M
authors.initials: LM
authors.lastname: Martins
authors.forename: Nelson R F A
authors.initials: NR
authors.lastname: Silva
authors.forename: Leonard
authors.initials: L
authors.lastname: Marotta
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
mesh_terms: D003442:Crowns; D000044:Dental Abutments; D019250:Dental Implants, Single-Tooth; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D007180:Incisor; D008855:Microscopy, Electron, Scanning; D015203:Reproducibility of Results