title: Biomechanical evaluation of macro and micro designed screw-type implants: an insertion torque and removal torque study in rabbits.
abstract: OBJECTIVE
  To investigate the combined effect of macro and pitch shortened threads on primary and secondary stability during healing, but before dynamic loading.
  
  
  METHODS
  Two sets of turned implants with different macro geometry were prepared. The test group possessed pitch shortened threads in between the large threads and the control group did not have thread alterations. The two implant groups were placed in both femur and tibiae of 10 lop-eared rabbits, and at the time of implant insertion, insertion torques were recorded. After 4 weeks, all implants were subjected to removal torque tests.
  
  
  RESULTS
  The insertion torque values for the control and test groups for the tibia were 15.7 and 20.6 Ncm, respectively, and for the femur, 11.8, and 12.8 Ncm respectively. The removal torque values for the control and test groups in the tibia were 7.9 and 9.1 Ncm, respectively, and for the femur, 7.9 and 7.7 Ncm respectively. There was no statistically significant difference between the control and test groups.
  
  
  CONCLUSIONS
  Under limited dynamic load, the addition of pitch shortened threads did not significantly improve either the primary or the secondary stability of the implants in bone.
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Odontology, Malmö University, SE-20506 Malmö, Sweden. ramesh.chowdhary@mah.se
authors.forename: Ramesh
authors.initials: R
authors.lastname: Chowdhary
authors.forename: Ryo
authors.initials: R
authors.lastname: Jimbo
authors.forename: Christian
authors.initials: C
authors.lastname: Thomsen
authors.forename: Lennart
authors.initials: L
authors.lastname: Carlsson
authors.forename: Ann
authors.initials: A
authors.lastname: Wennerberg
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D020878:Device Removal; D005269:Femur / Q000502:physiology; D007368:Interferometry; D011817:Rabbits; D013314:Stress, Mechanical; D013499:Surface Properties; D013524:Surgical Flaps; D013977:Tibia / Q000601:surgery; D014025:Titanium; D019415:Torque
chemical_list: D015921:Dental Implants; D014025:Titanium