title: Fracture resistance of titanium and zirconia abutments: an in vitro study.
abstract: BACKGROUND
  Little information comparing the fracture resistance of internal connection titanium and zirconia abutments exists to validate their use intraorally.
  
  
  OBJECTIVE
  The purpose of this study was to determine the fracture resistance of internal connection titanium and zirconia abutments by simulating cyclic masticatory loads in vitro.
  
  
  METHODS
  Twenty-two specimens simulating implant-supported anterior single crowns were randomly divided into 2 equal test groups: Group T with titanium abutments and Group Z with zirconia abutments. Abutments were attached to dental implants mounted in acrylic resin, and computer-aided design/computer-aided manufacturing (CAD/CAM) crowns were fabricated. Masticatory function was simulated by using cyclic loading in a stepped fatigue loading protocol until failure. Failed specimens were then analyzed by using scanning electron microscopy (SEM) and fractographic analysis. The load (N) and the number of cycles at which fracture occurred were collected and statistically analyzed by using a 2-sample t test (α=.05).
  
  
  RESULTS
  The titanium abutment group fractured at a mean (SD) load of 270 (56.7) N and a mean (SD) number of 81 935 (27 929) cycles. The zirconia abutment group fractured at a mean (SD) load of 140 (24.6) N and a mean (SD) number of 26 296 (9200) cycles. The differences between the groups were statistically significant for mean load and number of cycles (P<.001). For the titanium abutment specimens, multiple modes of failure occurred. The mode of failure of the zirconia abutments was fracture at the apical portion of the abutment without damage or plastic deformation of the abutment screw or implant.
  
  
  CONCLUSIONS
  Within the limitations of this in vitro study, 1-piece zirconia abutments exhibited a significantly lower fracture resistance than titanium abutments. The mode of failure is specific to the abutment material and design, with the zirconia abutment fracturing before the retentive abutment screw.
authors.affiliation: Lecturer and Clinical Supervisor, Melbourne Dental School, University of Melbourne, Melbourne, Australia. jfoong@prosgroup.com.au
authors.forename: Jamie K W
authors.initials: JK
authors.lastname: Foong
authors.forename: Roy B
authors.initials: RB
authors.lastname: Judge
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Palamara
authors.forename: Michael V
authors.initials: MV
authors.lastname: Swain
mesh_terms: D001732:Bite Force; D017076:Computer-Aided Design; D003442:Crowns; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D019250:Dental Implants, Single-Tooth; D003764:Dental Materials / Q000737:chemistry*; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D006801:Humans; D008409:Mastication / Q000502:physiology; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide