Factors affecting stability of surgical guides in mandibular unilateral distal extension situation: An in vitro study

Unilateral tooth-supported guides reported less effective implant placement than bilateral tooth-supported guides. Therefore, this study evaluated the effect of guide design, replaced tooth location, and applied forces on implant deviation and guide stability of mandibular unilateral tooth-supported guides.

Ten epoxy resin models with soft tissue simulated material were used. For each model, three surgical guide designs were generated: a fully extended guide, a guide with two fixation pins, and one with one fixation pin. Two sleeves were incorporated in each guide for mandibular premolar and molar. Forces were applied from the buccal and oral directions (0.1 N, 1 N, 2.5 N, and 5 N). An intraoral scanner captured the resulting surgical guide displacement. Virtual implants were added to each scan (470 virtual implants) to measure their deviation from the original planned position.

Surgical guides with two fixation pins showed the least implant vertical deviation (0.38 ± 0.27 mm, p<0.001) and guide deviation (0.52 ± 0.25 mm, p<0.001). Guide design has a small to medium effect size in all the deviation measurements(p<0.001). Force direction has a significantly large effect on implant vertical deviation (η² = 0.15, p<0.001). Force magnitude greatly affects implant angular deviation (η² = 0.34, p<0.001). A larger vertical deviation was detected in the molar implant location (0.59 ± 0.48 mm p<0.001).

Incorporating two fixation pins into unilateral tooth-supported guides significantly enhances stability and minimizes implant deviation. However, forces applied during guided surgery and implant location have a substantial impact, exceeding the influence of the guide design.