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Volume 25 , Issue 5
September/October 2010

Pages 883887

Insertion Torque in Different Bone Models with Different Screw Pitch: An In Vitro Study

Bruno Orlando, DDS/Antonio Barone, DDS, PhD/Thierry M. Giorno, DDS/Luca Giacomelli, PhD/Paolo Tonelli, MD, DDS/Ugo Covani, MD, DDS

PMID: 20862400

Purpose: 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. Materials and 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 D1D2 and D3D4 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. Conclusion: 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). Int J Oral Maxillofac Implants 2010;25:883887

Key words: cancellous bone, cortical bone, implant stability, insertion torque, screw pitch

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