Technique comparison for efficient orthodontic tooth measurements using digital models

Objective: To determine the best technique for measuring mesial-distal tooth widths on digital models. Methods: The individual mesial-distal tooth widths were measured (first molar to first molar, maxillary and mandibular) on 32 stone casts and corresponding digital models (emodels, GeoDigm, Chanhassen, Minn). The digital models were measured using five different techniques: occlusal aspect, occlusal aspect zooming in on each individual tooth, facial aspect rotating as needed, facial aspect from three standard positions (R buccal, facial, and L buccal), and qualitatively rotating the model in any position deemed necessary. Measurements were repeated three times at least 1 week apart. The operator time needed to complete each set of measurements was recorded. Results: Four of five digital measurement techniques (except for the facial aspect from three standard positions) showed a slight positive bias (overestimation in measured width) compared with stone cast measurements. Measuring from the occlusal aspect resulted in the greatest Pearson correlation (98.509%), the least Altman-Bland standard deviation of differences value (1.881 mm), and the second fastest measuring time (2 minutes 3 seconds). Qualitatively rotating the model had similar Pearson correlation and Altman-Bland values to the Occlusal technique but took the longest time to measure (7 minutes 1 second). Conclusions: The Occlusal measurement technique for digital models was the best combination of accuracy, repeatability, and speed of measurement. (Angle Orthod. 2010;80:254-261.)