Influence of Underpreparation on Primary Stability of Implants Inserted in Poor Quality Bone Sites: An In Vitro Study

Purpose: The purpose of this present study was to investigate the relation between implant site underpreparation and primary stability in the presence of poor-quality bone. Materials and Methods: A study was performed on fresh humid bovine bone; samples presented no cortical layer with a cancellous structure inside and were obtained from the hip. The bones were firmly attached to a base device. Sixty sites were prepared according to the protocol provided by the manufacturer: a 2-mm pilot drill was introduced to the proper depth and then twist drills of 3 and 3.4 mm were used. After site preparation, 20 3.4-x 11-mm (standard protocol group), 20 3.8-x 11-mm(10% undersized group), and 20 4.5-x 11-mm (25% undersized group) implants were inserted at a calibrated maximum torque of 70 N-cm at the predetermined speed of 30 rpm. After implant insertion, variable torque work (VTW), maximum insertion torque (peak IT), and resonance frequency analysis (RFA) values were recorded. Results: The standard protocol group showed a mean VTWof 565.77 +/- 219.12 N-cm, a peak IT of 11.3 +/- 4.44 N-cm, and an RFA of 69.35 +/- 7.35 implant stability quotient (ISQ). The 10% undersized group showed a mean VTWof 1,240.24 +/- 407.78 N-cm, a peak IT of 20.26 +/- 7.03 N-cm, and an RFA of 73.40 +/- 2.33 ISQ. The 25% undersized group showed a mean VTWof 1,254.96 +/- 727.49 N-cm, a peak IT of 17.15 +/- 10.39 N-cm, and an RFA of 72.30 +/- 6.70 ISQ. For VTW, the difference between the standard and undersized protocol values was statistically significant; for peak IT, the difference between the standard and 10% undersized protocol values was statistically significant; no other statistical differences were found between mean values. Conclusions: In the presence of poor-bone quality, a 10% undersized protocol is sufficient to improve the primary stability of the implant; additional decreases do not seem to enhance primary stability values. (C) 2015 American Association of Oral and Maxillofacial Surgeons