Red fluorescence threshold for assessing the lesion activity of early caries

The aim of this study was to determine a red fluorescence threshold for differentiating active from inactive non-cavitated carious lesions.

Using the Nyvad criteria, 30 human teeth with non-cavitated carious lesions were divided into active lesions (15 teeth) and inactive lesions (15 teeth). Using the blue light of a quantitative light-induced fluorescence-digital camera, the red fluorescence of the lesions was measured as the ΔR value. By live/dead bacterial staining, bacterial viability was calculated as the Ratio_G/G+R. The ΔR and Ratio_G/G+R of active and inactive lesions were compared. The relationship between ΔR and Ratio_G/G+R was also analyzed. The ΔR threshold was determined for the classification of lesion activity, and its validity was tested.

The mean ΔR of active lesions was 1.85 fold higher than that of inactive lesions (p < 0.001), and the Ratio_G/G+R of active lesions was 1.97 fold higher than that of inactive lesions (p < 0.001). There was a significant positive correlation between the ΔR and the Ratio_G/G+R in non-cavitated carious lesions (p < 0.05). The ΔR threshold for the differentiating non-cavitated carious lesions by activity status was 37.55, and the sensitivity and specificity were both 83.33 %.

A red fluorescence threshold for categorizing non-cavitated carious lesion activity based on microbial metabolic activity was determined. Accurate evaluation of the activity status of non-cavitated carious lesions will assist in diagnosis and treatment planning for patients with dental caries.