Impact of Level of Guidance on the Accuracy of Static Computer-Assisted Implant Surgery (s-CAIS): An In Vitro Study

Accurate implant placement is essential for predictable functional and esthetic outcomes. Although static computer-assisted implant surgery (s-CAIS) is more accurate than freehand placement, the effects of increasing guidance within partially guided workflows and on adjacent-implant relationships remain unclear. This in vitro study compared accuracy across six workflows and assessed inter-implant parallelism and vertical platform discrepancy.

Twenty mandibular models were used per workflow, with two implants placed in each model (40 implants per workflow). Workflows comprised non-guided placement, universal and system-specific pilot-drill guidance, intermediate-drill guidance, and two fully guided systems. Planned positions were compared with postoperative STL datasets. Outcomes included 3D platform and apical deviations, angular and directional deviations, precision, and adjacent-implant vertical and angular discrepancies. Two-way ANOVA and a linear mixed model were applied.

Workflows differed significantly across parameters. Fully guided systems showed the lowest 3D and angular deviations and highest precision, with deviations as low as 0.23 ± 0.10 mm and 1.25° ± 0.61°. Greater guidance was associated with reduced linear and angular deviation. Vertical platform discrepancy was lowest with fully guided workflows (0.05-0.06 mm), followed by partially guided workflows (0.08-0.09 mm) and freehand placement (0.15 mm). Conversely, fully guided workflows showed numerically greater inter-implant angular discrepancy (1.37°-1.69°) than partially guided workflows (1.00°-1.13°).

Accuracy varied by guidance level. Fully guided workflows provided the highest trueness and precision and most consistent vertical platform positioning. Greater plan-to-implant accuracy was not accompanied by improved inter-implant parallelism, indicating that these outcomes should be evaluated separately.