Automatic Calibrated Measurement of Murine Tooth Colour and Whiteness

The mouse provides a valuable model for dental anomalies. Measurement of such small teeth enhances the systematic errors managed during standardised human dental imaging. Tooth colour is uneven so it is important to not only be able to access tooth colour of a whole surface, but also of defined portions of a surface. Objectives: To determine the reliability of an automated, calibrated tooth colour measurement system for the labial surfaces of murine teeth as a whole and for 3 automatically defined sections. Methods: The lower left central incisors were extracted from the mandibles of 20 wild type mice. The teeth were kept hydrated until imaged and then placed in a custom tooth holder and imaged under D60 lighting. A standard tile was imaged for calibration purposes. The tile was viewed using Adobe Photoshop CS2 software and an area of interest (AOI) selected around the tile. The mean R, G and B values were automatically collected and fed into the algorithm for transformation into Commission internationale de l'Eclairage (CIE) values L, a, b and w, when prompted. The algorithm compares the tile values with those provided by the manufacturer to give an error correction. The tooth images were then loaded and an AOI selected around the tooth boundary. The calibrated CIE values were then calculated and automatically sent to Excel for viewing. Each labial view was automatically split into the gingival, middle and incisal third and CIE values calculated for the separate portions. This process was repeated twice by two examiners using polarised and non-polarised lighting and the inter-class correlation coefficients calculated (ICCC). Results: Table 1. Conclusion: The method proved reliable for the assessment of murine tooth colour. Low values indicate the difficulty in the initial orientation of such small teeth. Sponsored by the Wellcome Trust Foundation. Grant number GRO75945MA