title: Implant abutment deformation during prosthetic cylinder screw tightening: an in vitro study.
abstract: OBJECTIVE
  Nonpassive fit frameworks are believed to lead to implant overload and consequently loss of osseointegration. This is one of the most commonly reported failures of implant prostheses. In an ideal situation of passive fit, when torque is applied to bring the abutment-cylinder interface together some amount of deformation can be expected, and it should be homogeneous along the periphery of the abutment. The aim of this study was to verify the amount of abutment deformation that can be expected when a free-standing cylinder is screwed into place. This could give insight into what should be accepted as passive fit.
  
  
  METHODS
  Strain gauges were bonded to the sides of five standard abutments that had machined palladium-silver cylinders or cobalt-chromium cast cylinders screwed into place. Measurements were taken to verify the deformation at each site.
  
  
  RESULTS
  Values of abutment deformation after abutment screw tightening ranged from -127.70 to -590.27 microepsilon. The deformation recorded for palladium-silver prosthetic cylinder tightening ranged from 56.905 to -381.50 microepsilon (mean: 173.298 microepsilon) and from -5.62638 to -383.86 microepsilon (mean: 200.474 microepsilon) for cobalt-chromium cylinders. There was no statistically significant difference among the two groups.
  
  
  CONCLUSIONS
  Both abutment screw tightening and prosthetic cylinder screw tightening result in abutment deformation, which is compressive most of the time.
authors.affiliation: Department of Prosthodontics, Bauru School of Dentistry, Universit of São Paulo, Bauru, SP, Brazil.
authors.forename: Rafael Tobias Moretti
authors.initials: RT
authors.lastname: Neto
authors.forename: Marcio Silva
authors.initials: MS
authors.lastname: Moura
authors.forename: Edson Antonio Capello
authors.initials: EA
authors.lastname: Souza
authors.forename: José Henrique
authors.initials: JH
authors.lastname: Rubo
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry; D000044:Dental Abutments; D003722:Dental Alloys / Q000737:chemistry; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D010165:Palladium / Q000737:chemistry; D011312:Pressure; D012834:Silver / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D015921:Dental Implants; D003764:Dental Materials; D012834:Silver; D010165:Palladium; D014025:Titanium