骨欠損の異なる構成に配置されたインプラントのマクロデザインとISQ値への影響：インビトロ実験的研究

To evaluate the variations in ISQ values of parallel-walled (PW) and tapered (TW) implants subjected to simulated peri-implant bone defects of different depths and configurations in two bone densities (D2 and D3).

Eighty implants (40 PW and 40 TW; Ø 4.25 mm, length 11.5 mm; GMI Dental, Spain) were placed in polyurethane blocks simulating D2 and D3 bone densities. Eight peri-implant defect scenarios were created: one-, two-, and three-wall defects and circumferential bone loss, at 1/3 (4 mm) and 2/3 (8 mm) of implant length. ISQ values were measured with the Osstell Beacon® device in two directions (buccolingual and mesiodistal), and mean values were recorded. Statistical analyses included Student's t-test, Mann-Whitney U test, Chi-square/Fisher's exact test, Friedman test, and linear regression models.

Initial ISQ values (M0) indicated high stability (>70) for both implant designs in D2 and D3 bone. Progressive bone loss significantly reduced ISQ values (p<0.001). In D2 bone, TW implants showed greater stability in some 1/3 bone loss scenarios (M2), but PW implants outperformed TW implants in deeper (2/3) defects affecting multiple walls. In D3 bone, PW implants consistently showed superior stability under 2/3 bone loss conditions (M1, M3, M4). Multivariate regression confirmed that bone density and extent of bone loss were the strongest predictors of ISQ reduction, while implant design became significant in advanced circumferential loss.

Bone density and the extent of peri-implant bone loss are key determinants of implant stability. Implant macrodesign plays a relevant role as bone support decreases: tapered implants (TW) were more negatively affected than parallel-walled implants (PW) under advanced bone loss. While ISQ values remained above the low stability threshold (<60) with 1/3 bone loss, stability dropped markedly when 2/3 of the implant length was compromised.