Primary stability comparison of three implant microgeometries in synthetic bone blocks: an in vitro study

Achieving optimal primary stability is critical for successful osseointegration. This initial mechanical fixation is significantly influenced by the implant macrogeometry and the surgical drilling protocol. This in vitro study aimed to evaluate and compare the primary stability of three distinct implant systems, each with specific macrogeometries and manufacturer-recommended drilling protocols, across varying simulated bone densities. Ninety implants ( n = 30 per group), conventional tapered (DC), tapered with healing chambers (MAE), and cylindrical-conical (VEL), were tested in synthetic polyurethane blocks (10, 20, and 30 PCF). Primary stability was assessed via insertion torque (IT) and implant stability quotient (ISQ). The VEL system consistently demonstrated superior primary stability across all densities, achieving the highest mean IT (74.5 ± 2.8 Ncm) and ISQ (76.3 ± 1.2) at 30 PCF. The MAE system demonstrated biomechanical efficiency in low-density bone (10 PCF), achieving adequate ISQ values (54.0 ± 0.8) while generating comparatively lower IT (6.0 ± 2.1 Ncm), potentially minimizing surgical trauma. Significant differences ( p < 0.001) were observed between groups and densities. The tested implant systems, evaluated using their respective manufacturer-recommended osteotomy protocols, demonstrated significantly different primary stability across bone densities. Because implant design and drilling protocol differed among systems, the present study compares the overall biomechanical performance of each implant system rather than the isolated effect of implant microgeometry. The undersized drilling protocol of the VEL system offers high stability through increased bone compression, while the MAE design provides efficient stability with minimal torque in low-density bone.