A new in vivo method for measuring caries activity using quantitative light-induced fluorescence.

The aim of this in vivo study was to assess the association between caries prevalence and activity parameters and the properties of etched sites measured with quantitative light-induced fluorescence (QLF). In a clinical method, two areas of a deciduous tooth were etched in each of 44 children (mean age 8.23 years+/-1.45) with 36% phosphoric acid gel for 1 min and 4 min, respectively. DeltaQ of the etched site was measured immediately after the etching (DeltaQ1) and 24 h later (DeltaQ2) with QLF. In addition, deft/DMFT, approximal plaque (API), bleeding on probing (mod. PBI), active carious lesions and currently used fluorides were recorded. In a regression analysis for the deft, the use of fluoridated salt (standardized coefficient SC=-0.25) and fluoride gel (SC=-0.37) showed the greatest effect, as did the fluoride gel (SC=-0.26) and gingival bleeding (SC=0.50) for the number of active carious lesions. The deft and the number of active carious lesions correlated significantly (r=0.70, p<0.001). DeltaQ1 and DeltaQ2 showed a significant statistical correlation with the age-adjusted deft (0.39<r<0.52, p<0.01) and with the number of active lesions (0.42<r<0.59, p<0.01). Correlations between DeltaQ and the API, PBI and the fluoride scores were slightly weaker but also statistically significant. In a principal-component analysis, these parameters were approximately identical, indicating a strong relationship between the different variables and DeltaQ. This relationship was especially strong for the deft and the active carious lesion scores. In conclusion, these data suggest that the degree of demineralization by etching and its changes with time are associated with caries activity and that this method might be used for the early assessment of caries activity.