Recovery percentage of remineralization according to severity of early caries

Purpose: To analyze the cutoff severity of early lesions according to recovery rate after fluoride treatment. Methods: 100 specimens were demineralized over 3 to 40 days. Specimens were immersed in 2% sodium fluoride solution for 4 minutes, and then in artificial saliva for the rest of the total 24 hours. After 10-time repetition of this cycle, the AF recovery rates (R _ΔF, %) were calculated from the ΔF values before (ΔF_base, %) and after (ΔF_tx, %) remineralization using the QLF-D system. For the discrimination of R _ΔF based on ΔF_base, the sensitivities versus 1-specificities were analyzed in receiver operating characteristic (ROC) curves, the 95% confidence interval (CI) as well as the significance of differences. The histological features of lesions were observed and lesion depths were digitally measured by polarized light microscopy (PLM). A paired t-test was also performed to assess the differences in ΔF and lesion depth before and after applying fluoride. Results: For a threshold recovery percentage of 40%, the suggested ΔF_base cutoff value was -19.15%, whereas for a threshold recovery percentage of 50%, the suggested cutoff value was -14.60% (P< 0.0001). According to the QLF-D system and PLM analysis, recovery percentage was greater for shallower lesions. Based on fluoride treated recovery percentages, the findings suggested that it is possible for early caries lesions to make more than 50% recovery when the ΔF_base value was greater than -14.60%. Visually and numerically, the relative recovery percentages were highest during the earlier stages of caries.