Characterization of teeth fluorescence properties due to coffee pigmentation: towards optimization of quantitative light-induced fluorescence for tooth color assessment

Abstract

The assessment of tooth color is typically performed by subjective comparison with a visual shade guide or by using objective optical techniques such as quantitative light-induced fluorescence (QLF). QLF measurements rely on the precise wavelength calibration of fluorescence excitation and emission for enhancing the contrast between the white sound tooth and stained areas. These areas may change the fluorescence emission differently depending on the color that is most absorbed by the stain on the tooth surface. Although previous studies have monitored the staining contrast generated by the consumption of beverages on teeth, the information provided is based on total intensity. However, this intensity varies from each QLF device configuration and comparison across studies may not be possible. Few studies report the wavelength-dependent characterization of the staining process, which allow the comparison on the light attenuation on specific wavelengths and can be used to design fluorescence equipment with improved contrast for the tooth color assessment. In this study, we quantified the fluorescence spectral features (fluorescence intensity, wavelength shift of the maximum intensity, full width at half maximum, and wavelength-dependent intensity attenuation) of teeth in several degrees of coffee pigmentation by using 445 nm excitation. Most of the pigmentation effect was observed on the fluorescence intensity and a linear behavior was observed for the full width at half maximum (around 11.8% increase for each pigmentation level). We characterized the fluorescence properties of each degree of pigmentation level. Both spectral features and fluorescence properties can be used to design novel fluorescence equipment capable of increasing the contrast between white and stained teeth.