Objective Colour Matching of Composite Using Digital Imaging

Objectives: To investigate the ability to match composite restorations to the tooth using digital imaging and CIELAB colour difference. Methods: Ten extracted human central incisors were used. Discs of composites¹ 7mm in diameter x 3mm thick were made for the eleven shades and mounted to produce a customised shade guide (CSG). The CSG was photographed next to each of the 10 teeth in a phantom head using a SLR digital camera². The sRGB colour values were obtained from the images using SigmaScan^® Pro image analysis software and the data was then converted to the CIELAB colour values. Colour difference (DE) between the teeth and shade discs was calculated from the L* a* b* values. Three cavities were drilled into the labial surface of each tooth. Composite shades with lowest three DE were used to restore the cavities. Ten observers evaluated the teeth under a standard D65 light source. The observers recorded the best match, the perceptibility, acceptability of the best match and the worst match. Finally, the ten teeth with three restorations on the labial surface were photographed again and the colour difference was calculated between the composite filling and the surrounding tooth surface. Results: showed that the majority of the observers selected the lowest DE in 6 out of the 10 teeth and 2 out of 10 for the 2nd lowest DE. The restorations selected by the observer were agreed clinically acceptable matches. There was a 100% correlation between the lowest colour difference (composite filling and the surrounding tooth surface) and the best match selected by majority of observes. Conclusion: the objective colour matching of composite has a great potential in matching specially matching the colour of a small area and across different areas.

¹Spectrum Dentsply, Weybridge, Surry, UK. ² Fuji S1 pro digital camera (FujiFilm, Japan).