In vitro quantification of white spot enamel lesions adjacent to fixed orthodontic appliances using quantitative light-induced fluorescence and DIAGNOdent

The aims of this in vitro study were 2-fold: 1) to evaluate two fluorescence methods (DIAGNOdent and QLF (quantitative light-induced fluorescence)) for quantification of white spot lesions adjacent to fixed orthodontic appliances; and 2) to determine the inter-observer agreement of the DIAGNOdent and QLF methods for quantification of incipient enamel lesions adjacent to fixed orthodontic appliances. Forty-one premolar teeth with visually sound smooth surfaces or visually white spot enamel lesions were included in the study. Orthodontic brackets were fixed adjacent to the lesions, thus simulating the position of fixed appliances during orthodontic treatment. All teeth were measured using both the DIAGNOdent and QLF methods. Of the 41 teeth, 20 smooth surfaces were randomly selected and analyzed by 4 operators using both DIAGNOdent and QLF. The teeth were sectioned into 300-mum-thick slices using a water-cooled diamond saw and the slices manually ground to 80-100 mum thickness. Histopathology and transverse microradiography were performed to provide the gold standards for verification of lesion depth and mineral loss, respectively. The Spearman rank correlation coefficients between lesion depth determined by histopathology and the DIAGNOdent and QLF were 0.76 and 0.82, respectively, whereas the Pearson correlation coefficients between mineral loss and the two methods were 0.64 and 0.84, respectively. Interobserver agreement was found to be 0.80 and 0.93 for DIAGNOdent and QLF, respectively. In conclusion, QLF may be a suitable method for quantifying incipient carious lesions adjacent to fixed orthodontic appliances.