Use of quantitative light-induced fluorescence to monitor tooth whitening

The changing of tooth shade by whitening agents occurs gradually. Apart from being subjective and affected by the conditions of the surroundings, visual observation cannot detect a very slight change in tooth colour. An electronic method, which can communicate the colour change quantitatively, would be more reliable. Quantitative Light-induced Fluorescence (QLF) was developed to detect and assess dental caries based on the phenomenon of change of autofluorescence of a tooth by demineralisation. However, stains on the tooth surface exhibit the same phenomenon, and therefore QLF can be used to measure the percentage fluorescence change of stained enamel with respect to surrounding unstained enamel. The present study describes a technique of assessing the effect of a tooth-whitening agent using QLF. This was demonstrated in two experiments in which either wholly or partially stained teeth were whitened by intermittent immersion in sodium hypochlorite. Following each immersion, the integrated fluorescence change (△Q) due to the stain was quantified using QLF. In either situation, the value of △Q (%.mm²) decreased linearly as the tooth regained its natural shade. It was concluded that gradual changing of the shade of discoloured teeth by a whitening agent could be quantified using QLF.