title: Fatigue Failure of Narrow Implants with Different Implant-Abutment Connection Designs.
abstract: OBJECTIVE
  To evaluate the reliability of narrow diameter dental implants (NDIs) with similar macrogeometry and 3 implant-abutment connection designs.
  
  
  METHODS
  Eighty-four NDIs (3.5 × 10 mm) were selected and divided into 4 groups (n = 21/group) according to implant-abutment connection design, as follows: EH - external hexagon, IH - internal hexagon, IC - internal conical, and IC-M - internal conical connected to a monolithic titanium abutment. Identical abutments were torqued to the implants, and standardized maxillary incisor crowns were cemented and subjected to step-stress accelerated life testing (SSALT) in water. Use of level probability Weibull curves, and reliability for a mission of 50,000 cycles at 75 N and 200 N were calculated.
  
  
  RESULTS
  The beta (β) values were: 1.48 for IC, 1.40 for IC-M, 8.54 for EH, and 1.98 for IH, indicating that damage accumulation was an acceleration factor for failure of all groups. At 75 N the probability of survival was not significantly different between groups. A decrease in reliability was observed for all groups at 200 N with no significant differences between IC (81.71%) and IC-M (94.28%), or between EH and IH (0%) which presented the lowest values. EH failures were primarily restricted to the screw, while IH involved screw and implant fracture. IC and IC-M were restricted to prosthetic failures (fracture and bending).
  
  
  CONCLUSIONS
  Narrow implants with external or internal hexagon connections presented the lowest reliability at high loads compared to internal conical connections. Failure modes differed among connections.
authors.affiliation: Prosthodontic and Periodontology Department, Piracicaba Dental School, University of Campinas, Piracicaba, Brazil.|Department of Biomaterials and Biomimetics, College of Dentistry, New York University, New York, NY.
authors.forename: Dimorvan
authors.initials: D
authors.lastname: Bordin
authors.affiliation: Department of Biomaterials and Biomimetics, College of Dentistry, New York University, New York, NY.
authors.forename: Lukasz
authors.initials: L
authors.lastname: Witek
authors.affiliation: Department of Prosthodontics, Bauru College of Dentistry, University of São Paulo, Bauru, Brazil.
authors.forename: Vinícius P
authors.initials: VP
authors.lastname: Fardin
authors.affiliation: Department of Prosthodontics, Bauru College of Dentistry, University of São Paulo, Bauru, Brazil.
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.affiliation: Department of Biomaterials and Biomimetics, College of Dentistry, New York University, New York, NY.|Hansjörg Wyss Department of Plastic Surgery, New York University School of Medicine, New York, NY.
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
mesh_terms: D003442:Crowns; D059605:Dental Implant-Abutment Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D007180:Incisor; D008422:Materials Testing; D014025:Titanium; D019415:Torque
chemical_list: D014025:Titanium
keywords: Biomechanics; fatigue; narrow-diameter dental implants; reliability; weibull