Comparison of measurements made on digital and plaster models

Measuring plaster models by hand is the traditional method of assessing malocclusion. Recent technologic advances now allow the models to be digitized, measured with software tools, stored electronically, and retrieved with a computer. OrthoCAD (Cadent, Fairview, NJ) performs this service. The purpose of this study was to evaluate the reliability of the OrthoCAD system. Two independent examiners measured tooth size, overbite, and overjet on both digital and plaster models. The results were compared, and interexaminer reliability was assessed. The study sample consisted of 76 randomly selected pretreatment patients. The results showed a statistically significant difference between the 2 groups for tooth size and overbite, with the digital measurements smaller than the manual measurements. However, the magnitude of these differences ranged from 0.16 mm to 0.49 mm and can be considered clinically not relevant. No difference was found between the 2 groups in the measurement of overjet. Interexaminer reliability was consistent for both the plaster and the digital models.