Clinical (QLF) and Histological Features of ICDAS Non-cavitated Smooth-surface Lesions

Objectives: The objective of this study was to address the correlation between ICDAS classification, QLF evaluation, and histological measurements of smooth surface non-cavitated carious lesions. Methods: Sixty-three extracted human teeth with smooth surface non-cavitated carious lesions were evaluated using the ICDAS criteria (codes 1 and 2, 2 being more severe, n=33 and 30 respectively). QLF images of the teeth, wet and dry, were captured and changes in fluorescence (ƒxF), volumetric change in fluorescence (ƒxQ), and Lesion Area were determined. Specimens were sectioned longitudinally using a hard tissue microtome. Polarized Light Microscopy (PLM) was used to evaluate the sections for depth of demineralization, and then classified the lesion according to depth, codes 1H (less than half in enamel) and 2H (more than half of enamel). The two-sample t-test was used to compare groups. Results: When the lesions were dry and evaluated with QLF, there was a significant difference in lesion area (p=0.0010), ƒxF (p=0.0002), and ƒxQ (p=0.0017) between code 1 and code 2 lesions. When the lesions were wet and evaluated with QLF, there was a significant difference in lesion area (p=0.0008), ƒxF (p=0.0002), and ƒxQ (p=0.0061) between code 1 and code 2 lesions. Additionally, there was a significant difference in histological classification between lesions classified as code 1 and code 2 (p<0.0001). Out of the teeth marked as code 1, 87.1% were categorized as code 1H. Out of the teeth marked as code 2, 46.2% were categorized as code 2H. Conclusion: Lesions coded with ICDAS code 2 gave QLF measurements indicating higher severity, and vice versa. Thus, the ICDAS system is appropriate for identifying early smooth surface lesions that directly correspond with QLF data denoting the presence of tooth decay. Furthermore, ICDAS code 1 lesions were found to be less deep histologically than code 2 lesions.