title: Influence of abutment material on the fracture strength and failure modes of abutment-fixture assemblies when loaded in a bio-faithful simulation.
abstract: OBJECTIVE
  The aim of the present study was to evaluate differences in the ultimate fracture resistance of titanium and zirconia abutments.
  
  
  METHODS
  Twenty titanium fixtures were embedded in 20 resin mandible section simulators to mimic osseointegrated implants in the premolar area. The embedded implants were then randomly divided into two groups. Afterwards, specimens in group A (n=10) were connected to titanium abutments (TiDesign™ 3.5/4.0, 5.5, 1.5 mm), while specimens in group B (n=10) were connected to zirconia abutments (ZirDesign ™ 3.5/4.0, 5.5, 1.5 mm). Both groups were loaded to failure in a dynamometric testing machine. Fractured samples were then analyzed by scanning electron microscopy (SEM).
  
  
  RESULTS
  Group A showed a significantly higher fracture strength than that observed in group B. Group A failures were observed at the screw that connects the abutment with the implant while the abutment connection hexagons were plastically bent by the applied load. Group B failures were a result of abutment fractures. SEM analysis showed that in group A the screw failure was driven by crack nucleation, coalescence and propagation, while in group B, the SEM analysis of failed surfaces showed the conchoidal fracture profile characteristic of brittle materials.
  
  
  CONCLUSIONS
  The strength of both tested systems is adequate to resist physiologic chewing forces in the premolar area. Conversely, the titanium and zirconia failure modes evaluated here occurred at unphysiological loads. In addition, because the abutments were tested without crowns, the presented data have limited direct transfer to the clinical situation.
authors.affiliation: Department of Dental Materials and Fixed Prosthodontics, School of Dental Medicine, Policlinico Le Scotte, Viale Bracci, University of Siena, Siena, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Apicella
authors.forename: Mario
authors.initials: M
authors.lastname: Veltri
authors.forename: Piero
authors.initials: P
authors.lastname: Balleri
authors.forename: Antonio
authors.initials: A
authors.lastname: Apicella
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
mesh_terms: D001696:Biomechanical Phenomena; D003198:Computer Simulation; D000044:Dental Abutments; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D008334:Mandible / Q000601:surgery; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016012:Poisson Distribution; D018709:Statistics, Nonparametric; D013499:Surface Properties; D014025:Titanium; D015040:Zirconium
chemical_list: D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide