Macrogeometric Differentiation of Dental Implant Primary Stability: An In Vitro Study

Purpose: To evaluate an alternative cutting, progressive thread design to increase primary stability in low-density bone. Materials and Methods: Four different implants with different macrogeometries (Nobel Biocare Active [NA] Internal RP implants [4.3 x 11.5 mm], Straumann BLX Roxolid RB implants [4.5 x 10 mm], Astra Tech Implant EV implants [4.2 x 11 mm], and PrimeTaper [PT 4.2 x 11 mm]) were placed in simulated osteotomies and extraction sockets in synthetic bone (Sawbones) according to the manufacturers' protocol. Insertion torque and ISQ values were measured using Implantmed Plus motor and Ostell IDX, respectively. Insertion time was recorded. Average values were calculated and compared using ANOVA and Tukey test. Results: Insertion torque (range: 5 to 44 Ncm) increased with increasing synthetic bone density for all implants. Different ISQ values in synthetic low-density bone were not observed in higher-density synthetic bone. Insertion torque of all implants was reduced when implants were placed in simulated sockets compared to simulated osteotomies. In both low- density and higher-density synthetic bone, the primary stability of PrimeTaper implants with cutting and progressive thread design was equivalent to that of the Nobel Biocare NobelActive implant with compressive thread design and greater than the BLX implant with compressive thread design. Conclusion: Different implant macrogeometries obtain relatively high primary stability in low-density bone when measured by ISQ. Double-thread implant designs reduce insertion times in higher-density bone. A cutting and progressive compressing thread design provides density-sensing performance compared to aggressive condensing thread designs. This macrogeometry can achieve high primary stability associated with modest insertion torque compared to aggressive threaded implant designs known to attain the highest insertion torque. The presence of multiple cutting threads may offer advantages in obtaining primary stability in low-density bone.