title: Reliability and Failure Modes of a Hybrid Ceramic Abutment Prototype.
abstract: OBJECTIVE
  A ceramic and metal abutment prototype was fatigue tested to determine the probability of survival at various loads.
  
  
  METHODS
  Lithium disilicate CAD-milled abutments (n = 24) were cemented to titanium sleeve inserts and then screw attached to titanium fixtures. The assembly was then embedded at a 30° angle in polymethylmethacrylate. Each (n = 24) was restored with a resin-cemented machined lithium disilicate all-ceramic central incisor crown. Single load (lingual-incisal contact) to failure was determined for three specimens. Fatigue testing (n = 21) was conducted employing the step-stress method with lingual mouth motion loading. Failures were recorded, and reliability calculations were performed using proprietary software. Probability Weibull curves were calculated with 90% confidence bounds. Fracture modes were classified with a stereomicroscope, and representative samples imaged with scanning electron microscopy.
  
  
  RESULTS
  Fatigue results indicated that the limiting factor in the current design is the fatigue strength of the abutment screw, where screw fracture often leads to failure of the abutment metal sleeve and/or cracking in the implant fixture. Reliability for completion of a mission at 200 N load for 50K cycles was 0.38 (0.52% to 0.25 90% CI) and for 100K cycles was only 0.12 (0.26 to 0.05)-only 12% predicted to survive. These results are similar to those from previous studies on metal to metal abutment/fixture systems where screw failure is a limitation. No ceramic crown or ceramic abutment initiated fractures occurred, supporting the research hypothesis. The limiting factor in performance was the screw failure in the metal-to-metal connection between the prototyped abutment and the fixture, indicating that this configuration should function clinically with no abutment ceramic complications.
  
  
  CONCLUSIONS
  The combined ceramic with titanium sleeve abutment prototype performance was limited by the fatigue degradation of the abutment screw. In fatigue, no ceramic crown or ceramic abutment components failed, supporting the research hypothesis with a reliability similar to that of all-metal abutment fixture systems. A lithium disilcate abutment with a Ti alloy sleeve in combination with an all-ceramic crown should be expected to function clinically in a satisfactory manner.
authors.affiliation: Department of Restorative Dentistry, Federal University of Minas Gerais-School of Dentistry (UFMG/FO), Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Nelson Rfa
authors.initials: NR
authors.lastname: Silva
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.|Department of Orthodontics, University of Pennsylvania School of Dental Medicine, Philadelphia, PA.
authors.forename: Hellen S
authors.initials: HS
authors.lastname: Teixeira
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
authors.forename: Lucas M
authors.initials: LM
authors.lastname: Silveira
authors.affiliation: Department of Prosthodontics, Bauru School of Dentistry, University of Sao Paulo, Bauru, Sao Paulo, Brazil.
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY.
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
authors.affiliation: Department of Tissue Engineering and Biophotonics, King's College London, Guy's Hospital, London, UK.
authors.forename: Van P
authors.initials: VP
authors.lastname: Thompson
mesh_terms: D002516:Ceramics; D017076:Computer-Aided Design; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006801:Humans; D014025:Titanium
chemical_list: C493120:lithia disilicate; D003776:Dental Porcelain; D014025:Titanium
keywords: Abutment; ceramics; fatigue; lithium-disilicate