Insertion torque in different bone models with different screw pitch: an in vitro study.
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).
Orlando
Bruno
B
Nanoworld Institute, University of Genoa, Italy. orlando@istitutostomatologicotirreno.it
Barone
Antonio
A
Giorno
Thierry M
TM
Giacomelli
Luca
L
Tonelli
Paolo
P
Covani
Ugo
U
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
D015921:Dental Implants