Accuracy of Surgical Guides in Guided Apical Surgery: An In Vitro Comparative Study

<b>Background/Objectives:</b> Guided endodontic microsurgery is a novel approach designed to improve safety and precision compared with conventional freehand techniques. The present study aimed to evaluate the accuracy, stability, and operative time of trephinations performed using stereolithographic surgical guides designed with Blue Sky Plan and Exoplan software compared with the conventional technique. <b>Methods:</b> A comparative in vitro study was conducted on 72 roots from 12 stereolithographic mandibles. Cone-beam computed tomography (CBCT) and intraoral scans were superimposed to design 16 surgical guides with verification windows and metallic sleeves. Trephinations were performed using a control freehand group, Blue Sky Plan, and Exoplan. Stability, accuracy, and operative time were assessed. Statistical analysis included ANOVA, Kruskal-Wallis, and chi-square tests. <b>Results:</b> Exoplan demonstrated superior accuracy (0.17 mm deviation), stability (12.5% failures vs. 50% in Blue Sky Plan), and shortest operative time (106 s vs. 127 s and 155 s). Differences were statistically significant (<i>p</i> < 0.05). Operative accuracy was independent of surgical duration. <b>Conclusions:</b> Exoplan outperformed Blue Sky Plan and freehand trephinations in stability, accuracy, and efficiency. These findings highlight the potential of digital guides for safer and more predictable endodontic microsurgery. Further clinical validation is required.