Macrodesign and osseodensification as determinants of implant primary stability: a multivariate in vitro study of 600 implants

ABSTRACT This study evaluated the influence of bone condensation techniques and implant macrogeometry on primary stability, using an in vitro polyurethane model simulating low-density bone, to provide practical guidelines for implant selection based on the surgical approach. A total of 600 tapered implants with five distinct macrodesigns were placed in standardized polyurethane blocks simulating D4-type bone using three protocols: undersized drilling, osseodensification with osteotomes, and osseodensification with Densah® burs. Insertion torque (IT) and implant stability quotient (ISQ) were recorded to assess primary stability. ANOVA and multivariable regression were used to examine the effects of implant design and technique, and Pearson’s correlation coefficient was used to assess the association between IT and ISQ. Both implant macrodesign and surgical protocol significantly influenced IT, with aggressive thread designs and the Densah® technique producing higher torque, whereas ISQ was affected only by macrodesign. A weak negative correlation was observed between IT and ISQ. The global regression model explained 71% of the variance in IT (R² = 0.71) and 23% of the variance in ISQ (R² = 0.23), with thread depth, thread angle, and lead emerging as the strongest predictors. These results indicate that implant macrodesign is a key determinant of primary stability, while the surgical protocol selectively enhances insertion torque. The weak correlation between IT and ISQ confirms that they reflect distinct biomechanical properties. Overall, these findings describe mechanical trends observed in an in vitro polyurethane model, and emphasize the importance of selecting implants based on both design and surgical technique. For future clinical research and given the development of AI-based planning tools in vivo validation may be required before clinical application.