Validation of a novel implant-retained fiducial marker system for digital scan alignment in the edentulous mandible: An accuracy study.

PURPOSE: This study validated the alignment accuracy of a novel implant-retained fiducial marker system for aligning digital scans in edentulous mandibles MATERIALS AND METHODS: A mandibular master cast with four implant analogs was fabricated. A reference scan of scan bodies (attached to analogs via spherical fiducial markers) was captured using a calibrated desktop scanner with a fixed-position jig. Without moving the cast, scan bodies were replaced with a milled interim prosthesis (using the same fiducial markers) and rescanned to ensure perfect spatial correspondence. The scan body assembly was rescanned 10 times using the desktop scanner (negative control dataset), then 10 times with an intraoral scanner (IOS). All IOS scans were aligned to the reference prosthesis scan in dental computer-aided design (CAD) software using fiducial marker-based reference alignment. Both negative control and aligned IOS scans were compared to the reference scan using metrology software to compute 3D deviation metrics. Statistical analysis used Mann-Whitney U test and Hodges-Lehmann estimator (α = 0.05).

RESULTS: Mann-Whitney U test revealed a statistically significant difference between groups (p < 0.001). Median RMS error for fiducial alignment was 85.8 µm, compared to 8.4 µm for the negative control. Hodges-Lehmann estimator median difference of -77.7 µm (95% CI: -82.4, -75.1 µm).

CONCLUSIONS: Despite statistical differences, the novel fiducial marker system achieved a mean alignment accuracy of approximately 85 µm, which is clinically acceptable. This in vitro study demonstrates technical feasibility. Clinical validation is warranted.