Comparison of three instruments (compass, digital caliper and 3d software) for dental linear measurements on plaster and digitalized models of infants and children: an agreement and reproducibility study

ABSTRACT Objective: The aim of the study was to evaluate the reproducibility and agreement of dental linear measurements made directly on plaster models with a compass, and a digital caliper, compared to digital measurements made through software on the same plaster models after digitalization. Methods: 40 plaster models from 20 infants and children aged between 1 and 5 years old, of both sex, with complete or incomplete primary dentition, with or without premature loss of primary anterior teeth were selected. The models were scanned using the Optical 3D scanner. Two calibrated operators performed dental linear measurements with a compass and a digital caliper directly on the plaster models and with the Autodesk Meshmixer software on the digital models. Six measurements were evaluated: missing tooth space (if any), arch perimeter, arch length, arch width, intercanine length and intercanine width. Statistical analysis was performed through the Jamovi program. Inter-rater reproducibility was calculated using the intraclass correlation coefficient (ICC) and agreement between instruments was analyzed using the Bland-Altman test. Results: Inter-rater ICC showed excellent consistency, ranging from 0.93 to 1.00. Agreement between instruments was good, with the mean difference ranging from 0.034 mm (limits: -1.077 to 1.145 mm) to -1.002 mm (limits: -0.831 to 0.185 mm). Conclusion: Dental linear measurements performed on digital models obtained from scanned plaster models demonstrated excellent reproducibility and good agreement compared to those made with a compass and a digital caliper. All measurement instruments can be reliably used in dental clinical practice.