Digitized Physical Impressions Optimize Apical Adaptation of Bio-Root Inlays for Apexification: A Comparison of Four Impression Techniques.

Objectives: To evaluate the three-dimensional adaptation of prefabricated Bio-Root inlays fabricated from impressions of simulated immature permanent root canals using four techniques: direct intraoral scanning (A), a light-body rubber impression digitized with an intraoral scanner (B), cone-beam computed tomography (CBCT)-based design (C), and a conventional indirect technique (D). Methods: Ten standardized simulated immature roots (extracted mandibular premolars prepared to a 1.5 mm apical diameter and 10 mm length) were used in a within-specimen comparative design, with each root receiving inlays fabricated by all four techniques. After fabrication and seating of the bioceramic inlays, the void percentage around each inlay was quantified by CBCT at the coronal, middle, and apical thirds relative to the baseline empty-canal volume. Data were analyzed using the Friedman, Wilcoxon signed-rank (Bonferroni-corrected), and linear mixed-model tests (α = 0.05). Results: Technique significantly affected void percentage (F(3,98) = 12.87, p < 0.001). Pooled across all canal thirds, Technique B had the lowest median void percentage (6.00 [7.00]), followed by A (8.00 [8.75]), C (12.00 [12.50]), and D (12.00 [19.00]). Independently of technique, the median void percentage increased from the coronal (6.00) to the middle (11.00) and apical (19.00) thirds. Differences among techniques were non-significant coronally (p = 0.437) but significant in the middle (p = 0.014) and apical (p < 0.001) thirds, with Technique B providing the best apical adaptation. Conclusions: The impression method significantly affected inlay adaptation. A light-body rubber impression digitized with an intraoral scanner yielded the best overall and apical fit, supporting digital workflows, particularly those using digitized physical impressions, for apexification. Adaptation deteriorated toward the apex regardless of technique.