title: Mechanical evaluation of four narrow-diameter implant systems.
abstract: OBJECTIVE
  This study aimed to evaluate the survival probability of four narrow-diameter implant systems when subjected to fatigue loading.
  
  
  METHODS
  Seventy-two narrow-diameter implants to be restored with single-unit crowns were divided into four groups (n = 18): Astra Tech (3.5-mm diameter), with a standard connection (ASC); BioHorizon (3.4-mm diameter), with a standard connection (BSC); Intra-Lock (3.4-mm diameter), with a standard multilobular connection (ISC); and Intra-Lock (3.4-mm diameter), with a modified square connection (IMC). The corresponding abutments were screwed onto the implants, and standardized metal crowns (maxillary central incisors) were cemented and subjected to step-stress accelerated life testing in water. Use-level probability Weibull curves and reliability for 100,000 cycles at 150 and 200 N (90% two-sided confidence intervals) were calculated. Polarized light and scanning electron microscopes were used to access the failure modes.
  
  
  RESULTS
  The calculated survival probability for 100,000 cycles at 150 N was approximately 93% in group ASC, 98% in group BSC, 94% in group ISC, and 99% in group IMC. At 200 N, the survival rate was estimated to be approximately < 0.1% for ASC, 77% for BSC, 34% for ISC, and 93% for IMC. Abutment screw fracture was the main failure mode for all groups.
  
  
  CONCLUSIONS
  Although the probability of survival was not significantly different among systems at a load of 150 N, a significant decrease was observed at 200 N for all groups except IMC.
authors.forename: Ronaldo
authors.initials: R
authors.lastname: Hirata
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.forename: Lucas S
authors.initials: LS
authors.lastname: Machado
authors.forename: Nick
authors.initials: N
authors.lastname: Tovar
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
mesh_terms: D002484:Cementation / Q000379:methods; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019415:Torque; D014867:Water / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D015921:Dental Implants; C483701:Rely X Unicem; D019279:Resin Cements; D014867:Water