title: Insertion torque in different bone models with different screw pitch: an in vitro study.
abstract: OBJECTIVE
  Orthopedic surgeons use different types of screws for bone fixation. Whereas hard cortical bone requires a screw with a fine pitch, in softer cancellous bone a wider pitch might help prevent micromotion and eventually lead to greater implant stability. The aim of this study was to validate the assumption that fine-pitch implants are appropriate for cortical bone and wide-pitch implants are appropriate for cancellous bone.
  
  
  METHODS
  Wide-pitch and fine-pitch implants were inserted in both hard (D1 and D2) bone and soft (D3 and D4) bone, which was simulated by separate experimental blocks of cellular rigid polyurethane foam. A series of insertion sites in D1-D2 and D3-D4 experimental blocks were prepared using 1.5-mm and 2.5-mm drills. The final torque required to insert each implant was recorded.
  
  
  RESULTS
  Wide-pitch implants displayed greater insertion torque (20% more than the fine-pitch implants) in cancellous bone and were therefore more suitable than fine-pitch implants.
  
  
  CONCLUSIONS
  It is more appropriate to use a fine pitch design for implants, in conjunction with a 2.5-mm osteotomy site, in dense cortical bone (D1 or D2), whereas it is recommended to choose a wide-pitch design for implants, in conjunction with a 1.5-mm osteotomy site, in softer bone (D3 or D4).
authors.affiliation: Nanoworld Institute, University of Genoa, Italy. orlando@istitutostomatologicotirreno.it
authors.forename: Bruno
authors.initials: B
authors.lastname: Orlando
authors.forename: Antonio
authors.initials: A
authors.lastname: Barone
authors.forename: Thierry M
authors.initials: TM
authors.lastname: Giorno
authors.forename: Luca
authors.initials: L
authors.lastname: Giacomelli
authors.forename: Paolo
authors.initials: P
authors.lastname: Tonelli
authors.forename: Ugo
authors.initials: U
authors.lastname: Covani
mesh_terms: D015519:Bone Density; D001863:Bone Screws; D001842:Bone and Bones / Q000033:anatomy & histology; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D017267:Dental Prosthesis Design; D006801:Humans; D019415:Torque
chemical_list: D015921:Dental Implants