title: Assessment of reliability of CAD-CAM tooth-colored implant custom abutments.
abstract: BACKGROUND
  Information is lacking about the fatigue resistance of computer-aided design and computer-aided manufacturing (CAD-CAM) tooth-colored implant custom abutment materials.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to investigate the reliability of different types of CAD-CAM tooth-colored implant custom abutments.
  
  
  METHODS
  Zirconia (Lava Plus), lithium disilicate (IPS e.max CAD), and resin-based composite (Lava Ultimate) abutments were fabricated using CAD-CAM technology and bonded to machined titanium-6 aluminum-4 vanadium (Ti-6Al-4V) alloy inserts for conical connection implants (NobelReplace Conical Connection RP 4.3×10 mm; Nobel Biocare). Three groups (n=19) were assessed: group ZR, CAD-CAM zirconia/Ti-6Al-4V bonded abutments; group RC, CAD-CAM resin-based composite/Ti-6Al-4V bonded abutments; and group LD, CAD-CAM lithium disilicate/Ti-6Al-4V bonded abutments. Fifty-seven implant abutments were secured to implants and embedded in autopolymerizing acrylic resin according to ISO standard 14801. Static failure load (n=5) and fatigue failure load (n=14) were tested. Weibull cumulative damage analysis was used to calculate step-stress reliability at 150-N and 200-N loads with 2-sided 90% confidence limits. Representative fractured specimens were examined using stereomicroscopy and scanning electron microscopy to observe fracture patterns.
  
  
  RESULTS
  Weibull plots revealed β values of 2.59 for group ZR, 0.30 for group RC, and 0.58 for group LD, indicating a wear-out or cumulative fatigue pattern for group ZR and load as the failure accelerating factor for groups RC and LD. Fractographic observation disclosed that failures initiated in the interproximal area where the lingual tensile stresses meet the compressive facial stresses for the early failure specimens. Plastic deformation of titanium inserts with fracture was observed for zirconia abutments in fatigue resistance testing.
  
  
  CONCLUSIONS
  Significantly higher reliability was found in group ZR, and no significant differences in reliability were determined between groups RC and LD. Differences were found in the failure characteristics of group ZR between static and fatigue loading.
authors.affiliation: Graduate student, Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash.
authors.forename: Nuno Marques
authors.initials: NM
authors.lastname: Guilherme
authors.affiliation: Professor, Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Wash. Electronic address: akchung@uw.edu.
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chung
authors.affiliation: Research Associate Professor, Materials Science and Engineering, University of Washington School of Engineering, Seattle, Wash.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Flinn
authors.affiliation: Assistant Professor, Biostatistics, Joseph J Zilber School of Public Health, University of Wisconsin, Milwaukee, Wis.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zheng
authors.affiliation: Professor, Department of Restorative Dentistry, University of Washington School of Dentistry, Seattle, Wash.
authors.forename: Ariel J
authors.initials: AJ
authors.lastname: Raigrodski
mesh_terms: D000497:Alloys; D017076:Computer-Aided Design; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006801:Humans; D008853:Microscopy; D008855:Microscopy, Electron, Scanning; D015203:Reproducibility of Results; D012117:Resins, Synthetic; D014025:Titanium; D015040:Zirconium
chemical_list: D000497:Alloys; D015921:Dental Implants; D012117:Resins, Synthetic; C493120:lithia disilicate; D003776:Dental Porcelain; C031462:titanium alloy (TiAl6V4); D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide