title: Torque removal force for osseointegrated implants--two experimental studies.
abstract: OBJECTIVE
  To introduce a rabbit-based model for testing the torque removal force (TRF) of implants and to compare the TRF of a series of titanium implants.
  
  
  METHODS
  Two experiments were performed at the University of the Witwatersrand. In the first, a Swedish- (SSM-N) or a South African-manufactured (SSM-S) implant was implanted into the tibiae of 12 rabbits and the TRF measured at 1, 3 and 6 months. In the second experiment, the TRF of 4 South African-manufactured titanium implants in the tibia or femur of 32 rabbits were compared at 3 and 6 weeks. The implants were: 1 threaded machined (SSM-S), and 3 surface-enhanced--1 threaded (SLA), 1 threaded tapered (MTT) and 1 pitted (RI).
  
  
  RESULTS
  In experiment 1, TRF increased significantly with time (p<0.05) but there was no significant difference between TRF for the South African and Swedish machined-surface implant types. In experiment 2, the TRF of the MTT implant was significantly greater (p<0.0001) than the other 3 types, which did not differ significantly from each other. Time had no significant effect.
  
  
  CONCLUSIONS
  In an internationally used rabbit-based model, South African and Swedish machined-surface titanium implants were equivalent; surface-enhanced implants produced higher TRF, and a tapered implant showed the highest TRF.
authors.affiliation: Division of Maxillofacial and Oral Surgery, University of Witwatersrand, Johannesburg.
authors.forename: J F
authors.initials: JF
authors.lastname: Lownie
authors.forename: P A
authors.initials: PA
authors.lastname: Betts
authors.forename: R S
authors.initials: RS
authors.lastname: Bryant
authors.forename: P
authors.initials: P
authors.lastname: Cleaton-Jones
mesh_terms: D000818:Animals; D020878:Device Removal; D008297:Male; D008422:Materials Testing / Q000379:methods*; D016348:Osseointegration; D019736:Prostheses and Implants; D011817:Rabbits; D013499:Surface Properties; D013977:Tibia / Q000503:physiopathology*; D014025:Titanium; D019415:Torque
chemical_list: D014025:Titanium