title: Reliability and failure behavior of CAD-on fixed partial dentures.
abstract: OBJECTIVE
  To estimate the reliability and failure behavior of fixed partial dentures (FPDs) fabricated using the CAD-on technique.
  
  
  METHODS
  FPDs (n=25) were fabricated using a CAD/CAM system: IPS e.max ZirCAD - Crystall./Connect and IPS e.max CAD (Ivoclar). The restoration type ("three-unit bridge") and design method ("multilayer") based on Biogenerics were used. Framework and porcelain structures were united using a fusion ceramic (Crystall./Connect, Ivoclar). Mechanical fatigue was tested in a servohydraulic load frame machine at a cyclic loading (frequency: 2Hz; load ratio: 0.1). Based on previous data from specimens tested in fast fracture, three different stress profiles were used. The lifetime data were analyzed using an inverse power law-Weibull cumulative damage model (ALTA PRO, Reliasoft). All failed specimens were examined under a field emission scanning electron microscope.
  
  
  RESULTS
  Porcelain chipping was the predominant (60%) mode of failure for FPDs tested in fast fracture and connector failure was predominant (67%) under fatigue. For fast fracture data, the Weibull modulus (β) of FPDs was 7.8 combining the two failure modes. When chipping and connector fracture data were analyzed separately, β values were 7.9 and 2.9. For the step stress fatigue test, β values were lower than estimated using fast fracture, being 1.6 for connector fracture and 1.3 for porcelain chipping.
  
  
  CONCLUSIONS
  The test method (fast fracture or fatigue) significantly influenced the reliability of FPDs fabricated using the CAD-on technique, but it did not influence their failure behavior.
authors.affiliation: School of Dentistry, Federal University of Pelotas, Rua Gonçalves Chaves 457, CEP 96015-560, Pelotas, RS, Brazil. Electronic address: gabybasso@yahoo.com.br.
authors.forename: G R
authors.initials: GR
authors.lastname: Basso
authors.affiliation: School of Dentistry, Federal University of Pelotas, Rua Gonçalves Chaves 457, CEP 96015-560, Pelotas, RS, Brazil.
authors.forename: R R
authors.initials: RR
authors.lastname: Moraes
authors.affiliation: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Passo Fundo, RS, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Borba
authors.affiliation: Department of Biomedical Materials Science, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Duan
authors.affiliation: Department of Biomedical Materials Science, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Griggs
authors.affiliation: Post-graduate Program in Dentistry, Dental School, University of Passo Fundo, Passo Fundo, RS, Brazil.
authors.forename: A
authors.initials: A
authors.lastname: Della Bona
mesh_terms: D002516:Ceramics; D017076:Computer-Aided Design; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D008422:Materials Testing; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium
keywords: Dental ceramics; Fatigue; Lithium disilicate; Step stress; Zirconia