Primary Stability of Cylindrical and Conical Dental Implants in Relation to Insertion TorqueA Comparative Ex Vivo Evaluation

Introduction:The aim of this ex vivo study was to investigate the influence of different insertion torques on primary stability of a conical and a cylindrical implant system.Materials and Methods:Thirty-two dental implants (Astra Tech OsseoSpeed 5.0 S x 11 mm cylindrical [n = 16] and 5.0 x 11 mm conical [n = 16]) were inserted with 20, 30, 40, and 45 N<bold>cm into fresh porcine bone of mixed trabecular</bold>-cortical quality. Before insertion, bone quality was assessed via cone beam tomography. After insertion, resonance frequency analysis was reported using the implant stability quotient (ISQ). Implant insertion depths were evaluated, and the implants were pushed out of the bone by force (measured in N). All experiments were done with n = 4 per group.Results:The highest ISQ (mean 78.25 2.9) and pushout values (mean 675 N +/- 5.8) were measured for the cylindrical implant after insertion using 30 N<bold>cm</bold>. The conical implant showed the highest primary stability by means of ISQ (mean 76.25 +/- 2.2) and pushout force (mean 502.5 N +/- 9.6) after an insertion torque of 40 N<bold>cm</bold>. If more insertion force was used, primary stability was reduced in all cases.Conclusion:The data indicate that different forms of an implant system need different insertion torques to obtain an optimal primary stability. These results have to be verified clinically.