ABSTRACT
OBJECTIVES: We aimed to compare the differences in caries lesion changes when measured by QLF-D as fluorescence loss and by SS-OCT as lesion depth with respect to demineralized time, during formation of artificial early caries lesion. We also demonstrated that QLF-D and SS-OCT can be used effectively in monitoring the longitudinal progression of simulated caries lesions. METHODS: Ten bovine incisors were sectioned (5x4 mm) and embedded in epoxy resin. An acid-resistant nail varnish was applied to a part of the tooth surfaces to protect sound enamel (2x4 mm). To generate lesions, each specimen was immersed in 40 ml of a demineralizing gel for 20 days at 37degrees C. To measure mineral loss of the demineralized specimens, fluorescence loss (DeltaF, %) was measured by QLF-D and lesion depth (microm) was determined by SS-OCT from the captured cross-sectional image. All the specimens were analyzed daily by QLF-D image analysis software and SS-OCT image analysis program for 20 days. The repeated measures analysis of DeltaF and lesion depth was used. The paired t-test was used to assess differences between each day. The correlation between DeltaF and lesion depth was determined using the Pearson's correlation coefficient. RESULTS: On the 5th, 10th, and 15th day, compared to baseline values, DeltaF decreased in 12.7%, 25.0%, and 33.6% of the specimens, respectively, and the lesion depth increased in 9.9%, 16.0%, and 22.6% of the specimens, respectively. However, after 15 days, there was no change in the DeltaF and lesion depth. High significant correlation was identified between the resultant values of DeltaF obtained by QLF-D and those of lesion depth obtained by SS-OCT (r = -0.811, P<0.0001). CONCLUSIONS: The QLF-D and SS-OCT could detect subtle changes in mineral loss and lesion depth with respect to demineralized time. Furthermore, these devices were useful for monitoring changes in mineral amount and lesion depth.