Reliability and reproducibility of a best-fit superimposition method for digital models of adult patients treated without extractions

INTRODUCTION: Cone-beam computed tomography (CBCT) is considered the gold standard for 3-dimensional superimposition in assessing tooth movement during orthodontic treatment. However, given current guidelines emphasizing the reduction of radiation exposure, this study aimed to evaluate the accuracy, reliability, and reproducibility of a digital model superimposition technique that does not require CBCT. METHODS: This retrospective study included 10 adult patients who underwent comprehensive orthodontic treatment without extractions. All patients had full-head CBCT scans and corresponding maxillary and mandibular digital dental models. Two evaluators assessed tooth movement using a new superimposition technique based on Standard Triangle Language files, using the palatal rugae as a superimposition reference for the maxillary arch and the transfer of the mandibular position through the interarch occlusal relationship. The accuracy of this method was compared with that of a CBCT-based reference workflow involving the integration of scanned dental models into CBCT images. RESULTS: The mean variation in reference landmark positions across the 3 spatial planes was similar between the methods for both arches. Interevaluator differences (Δ) ranged from -0.07 to 0.06 mm, which were not considered clinically significant. Student t tests showed no statistically significant differences between evaluators for any axis in either method (P >0.05). Intraclass correlation coefficients demonstrated high agreement between the 2 methods, ranging from 0.88 to 0.98. CONCLUSIONS: The 3-dimensional digital model superimposition technique using the palatal rugae for the maxillary arch and the interarch occlusal relationship for the mandibular arch is a reliable and reproducible alternative to CBCT-based methods for evaluating orthodontic tooth movement in nongrowing patients treated without extractions.