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The use of QLF to quantify in vitro whitening in a product testing model by I. A. Pretty, W. M. Edgar and S. M. Higham Br Dent J 2001; 191: 566–569

Comment

The demand for tooth whitening has been steadily growing over recent years. Consequently, methods capable of examining the comparative efficacies of whitening toothpastes receive prominent attention. Although many studies have undertaken measurement of the whitening effects of toothpastes and bleaches, there is disagreement over the actual instrumental methods used for measurement. The authors of this paper have used a technique that has recently gained credibility in caries research.

Quantitative light induced fluorescence relies on the tooth tissue under scrutiny relaying an initially standardised fluorescent beam back to source with its own auto-fluorescent signature. This method has been used previously to differentiate between incipient caries and sound tooth tissue. From research generated by their own team, the authors have extrapolated this phenomenon to examine the differences between unstained and artificially stained enamel in the laboratory. Based upon a system in use for the last 20 years, staining was induced. However, modifications by the team allowed for use of tooth samples, so the method has clinical potential. Once performed, it is possible to examine stored images of samples and compare effects to the baseline.

After staining and treatment in succession, samples were then cleaned to baseline levels to be subjected to the other treatments. This way, a kind of crossover was achieved, allowing all samples to receive all treatments. Consequently, this study was able to not only compare treatment efficacies, but also to explore the validity of this equipment to measure stain.

Results indicated that the measurement technique was capable of discriminating between treatment groups, and statistics upheld this effect. It also could be seen that the successive treatments of the test toothpaste produced a progressively increasing stain removal effect, whereas the positive control, a peroxyborate mouthrinse, removed the majority of stain after a single application. Water was deservedly chosen as a negative control for its consistent inability to remove stain.

It remains to be seen whether the method bears up to reproducibility testing for inter and intra-examiner use. Also, it might have been useful to use other more widely accepted stain appraisal methods in parallel with this study for confirmation of the findings.