Guided implant surgery using three-dimensional (3-D) planning software and 3-D printed surgical guides has become a critical tool for enhancing accuracy. This study aims to determine the minimum guide hole height necessary to maintain implant placement accuracy.

Ten maxillary models with edentulous areas were created using CT and optical scan data. Six sites (for each model) were prepared for implant placement with surgical guides fabricated using a 3-D printer. Sixty implants were placed using these guides and divided into five groups according to the guide hole height (1 to 5 mm). After the placement, digital impressions were taken to assess the accuracy of implant positioning. Deviations between planned and actual implant positions were investigated using computer software, and data were statistically analyzed using ANOVA and Kruskal-Wallis tests.

Guide holes with 1 mm height (Group Ⅰ) resulted in the highest 3-D deviations (1.12 ± 0.36 and 1.99 ± 0.74 mm at the coronal and apical positions, respectively), with significant errors at the implant apical position compared to groups with taller guide holes (Groups Ⅳ and Ⅴ) (p = 0.005). There were no significant deviations between the 3 mm and 5 mm guide hole heights, with no statistical differences between groups at the x, y, and z-axis in the implant position.

A comparison between the group with a guide hole height of 5 mm on one side and the group with a height of 1 mm on both sides revealed a significant difference in implant placement accuracy.