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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 (5×4 mm) and embedded in epoxy resin. An acid-resistant nail varnish was applied to a part of the tooth surfaces to protect sound enamel (2×4 mm). To generate lesions, each specimen was immersed in 40 ml of a demineralizing gel for 20 days at 37°C. To measure mineral loss of the demineralized specimens, fluorescence loss (∆F, %) was measured by QLF-D and lesion depth (μm) 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 ∆F and lesion depth was used. The paired t-test was used to assess differences between each day. The correlation between ∆F and lesion depth was determined using the Pearson’s correlation coefficient.
Results
On the 5th, 10th, and 15th day, compared to baseline values, ∆F 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 ∆F and lesion depth. High significant correlation was identified between the resultant values of ∆F obtained by QLF-D and those of lesion depth obtained by SS-OCT (r = ―0.811, P<0.0001).
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Fig. 3.
Images taken by blue light of QLF-D over demineralization time. (A) base line, (B) day 1, (C) day 5, (D) day 10, (E) day 15, and (F) day 20. In the image, a left arrow indicates the sound area and a right arrow shows the demineralized area of the photographed specimen.
Fig. 4.
Images taken by SS-OCT over demineralization time. (A) base line, (B) day 1, (C) day 5, (D) day 10, (E) day 15, and (F) day 20. In the image, a left arrow indicates the sound area and a right arrow shows the demineralized area of the scanned specimen.
Table 1.
Changes in fluorescence and lesion depth by demineralization time
All values are the mean (standard deviation). ∆F means the loss of fluorescence in demineralized enamel part compared to sound part (%). LD means the lesion depth measured in images taken by SS-OCT (mm). *P-values denote statistically significant differences within rows by repeated measures analysis. †P-values denote statistically significant differences by paired t-test.
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