title: Influence of the height of the external hexagon and surface treatment on fatigue life of commercially pure titanium dental implants.
abstract: OBJECTIVE
  This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants.
  
  
  METHODS
  Electropolished commercially pure titanium dental implants (seven implants per group) with three different external hexagon heights (0.6, 1.2, and 1.8 mm) and implants with the highest external hexagon height (1.8 mm) and different surface treatments (electropolishing, grit blasting with aluminium oxide, and acid etching with sulfuric acid) were tested to evaluate their mechanical fatigue life. To do so, 10-Hz triangular flexural load cycles were applied at 37 degrees C in artificial saliva, and the number of load cycles until implant fracture was determined. Tolerances of the hexagon/abutment fit and implant surface roughness were analyzed by scanning electron microscopy and light interferometry. Transmission electron microscopy and electron diffraction analyses of titanium hydrides were performed.
  
  
  RESULTS
  First, the fatigue life of implants with the highest hexagon (8,683 +/- 978 load cycles) was more than double that of the implants with the shortest hexagons (3,654 +/- 789 load cycles) (P < .02). Second, the grit-blasted implants had the longest fatigue life of the tested materials (21,393 +/- 2,356 load cycles), which was significantly greater than that of the other surfaces (P < .001). The compressive surface residual stresses induced when blasting titanium are responsible for this superior mechanical response. Third, precipitation of titanium hydrides in grain boundaries of titanium caused by hydrogen adsorption from the acid solution deteriorates the fatigue life of acid-etched titanium dental implants. These implants had the shortest fatigue life (P < .05).
  
  
  CONCLUSIONS
  The fatigue life of threaded root-form dental implants varies with the height of the external hexagon and/or the surface treatment of the implant. An external hexagon height of 1.8 mm and/or a blasting treatment appear to significantly increase fatigue life of dental implants.
authors.affiliation: Department of Materials Science and Metallurgical Engineering, Techinical University of Catalonia, Barcelona, Spain. francesc.xavier.gil@upc.edu
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Gil
authors.forename: Conrado
authors.initials: C
authors.lastname: Aparicio
authors.forename: Jose M
authors.initials: JM
authors.lastname: Manero
authors.forename: Alejandro
authors.initials: A
authors.lastname: Padros
mesh_terms: D000134:Acid Etching, Dental; D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry; D000044:Dental Abutments; D045662:Dental Etching / Q000379:methods; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing / Q000379:methods; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D055664:Electrochemical Techniques; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D007368:Interferometry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D018583:Pliability; D012464:Saliva, Artificial / Q000737:chemistry; D013314:Stress, Mechanical; D013464:Sulfuric Acids / Q000737:chemistry; D013499:Surface Properties; D016019:Survival Analysis; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D012464:Saliva, Artificial; D013464:Sulfuric Acids; D006859:Hydrogen; D014025:Titanium; D000537:Aluminum Oxide; C033158:sulfuric acid