Accuracy of intraoral scanners when digitizing post preparations: A µ-CT based feasibility study

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OBJECTIVES: The aim of this in vitro study was to evaluate the scanning accuracy of two intraoral scanners at different post-preparation depths and diameters, using micro-computed tomography (µ-CT) data as the reference standard. METHODS: Twenty extracted human mandibular premolars were prepared to simulate advanced coronal substance loss. After endodontic treatment, post space preparations with varying depths (10 mm, 12 mm) and diameters (ISO 090, ISO 110) were created (n = 5). Two intraoral scanners, Primescan (PR) and TRIOS 4 (TR), were used for digital post-space acquisition. Reference datasets were generated using µCT. Trueness and precision were assessed by aligning intraoral scan data to µCT reference models using best-fit alignment and evaluating deviations at three predefined cross-sectional levels. Statistical analysis included three-way ANOVA, post-hoc testing, independent t-tests, and correlation analysis (α = 0.05). RESULTS: Regarding trueness, the three-way ANOVA revealed a significant effect of the scanner system and depth (p < 0.001), with PR demonstrating higher trueness than TR. A significant scanner-depth interaction was observed (p < 0.001). Preparation diameter showed no significant effect. For precision, significant main effects were found for scanner system and depth (p < 0.001). PR exhibited significantly higher precision than TR, particularly at increased depths. Preparation diameter had a minor but significant effect on precision (p = 0.041). A positive correlation was identified between trueness and precision (r = 0.838). CONCLUSIONS: The performance of intraoral scanners in post-space digitization was strongly scanner- and depth-dependent. PR demonstrated superior and more consistent trueness and precision across increasing preparation depths compared with TR. CLINICAL RELEVANCE: In clinical practice, the type of intraoral scanner and the preparation geometry should be considered when selecting a digital workflow, as these factors can influence the fit of the resulting restorations.

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