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Assessing agreement in measurements of orthodontic study models: Digital caliper on plaster models vs 3-dimensional
Wan Nurazreena Wan Hassan1, Siti Adibah Othman2, Chee Seng Chan3
1Senior lecturer, Department of Paediatric Dentistry and Orthodontics and Clinical Craniofacial Dentistry Research Group, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia.
Introduction:
In this study we aimed to compare measurements on plaster models using a digital caliper, and on 3-dimensional (3D) digital models, produced using a structured-light scanner, using 3D software.
Methods:
Fifty digital models were scanned from the same plaster models. Arch and tooth size measurements were made by 2 operators, twice. Calibration was done on 10 sets of models and checked using the Pearson correlation coefficient. Data were analyzed by error variances, repeatability coefficient, repeated-measures analysis of variance, and Bland-Altman plots.
Results:
Error variances ranged between 0.001 and 0.044 mm for the digital caliper method, and between 0.002 and 0.054 mm for the 3D software method. Repeated-measures analysis of variance showed small but statistically significant differences (P <0.05) between the repeated measurements in the arch and buccolingual planes (0.011 and 0.008 mm, respectively). There were no statistically significant differences between methods and between operators. Bland-Altman plots showed that the mean biases were close to zero, and the 95% limits of agreement were within ±0.50 mm. Repeatability coefficients for all measurements were similar.
Conclusions:
Measurements made on models scanned by the 3D structured-light scanner were in good agreement with those made on conventional plaster models and were, therefore, clinically acceptable.
