In Vitro Evaluation of Digitally Designed Surgical Guides for Free-end Mandibular Implants: Accuracy and Stability of...

Digital surgical guides are widely used in implant dentistry, but implant placement in mandibular free-end regions remains challenging because distal tooth support is limited and guide displacement may occur during drilling. This in vitro study evaluated the placement accuracy and stability of four digitally designed static surgical guide configurations and compared static computer-assisted implant surgery with dynamic navigation in a standardized mandibular distal-extension resin model. A partially edentulous mandibular model involving implant sites #36 and #37 was generated from intraoral scan and cone-beam computed tomography data. Four static guide designs were tested: a conventional unilateral cross-arch tooth-supported guide (GT I), two compact non-cross-arch guides with different supporting-tooth configurations (GT II and GT III), and a non-cross-arch guide with distal micro-screw fixation (GT IV). Postoperative scan data were superimposed onto the virtual plan to quantify angular, coronal, apical, depth, and lateral deviations. Progressive modification from GT I to GT IV reduced most angular and linear deviations at both implant sites. GT IV showed the lowest angular deviation and a favorable overall accuracy and stability profile in most comparisons, although GT III showed a slightly lower apical three-dimensional deviation at site #37. In the static-versus-dynamic comparison, dynamic navigation showed site-specific advantages in angular deviation and apical global deviation at #37, whereas static guidance showed comparable or better values for several measurements at #36. The combined-site comparison did not support uniform superiority of either modality. These findings indicate that guide-support configuration and distal stabilization influence placement accuracy and guide stability in a mandibular free-end resin model. Clinical validation is required before routine treatment recommendations can be made.