Dentin reactions to caries are misinterpreted by histological "gold standards"

Abstract

Dentin reactions to caries, crucial for pathogenesis and for the determination of the severity of caries lesions, are believed to be reasonably detected by stereomicroscopy (SM) and polarized light microscopy in quinoline (PLMQ), but accuracies are not available. Here, stereomicroscopy of wet (SW) and dry (SD) ground sections of natural occlusal caries lesions resulted in moderate (0.7, for normal dentin) and low accuracies (< 0.6, for carious and sclerotic dentin) as validated by contrast-corrected microradiography. Accuracies of PLMQ were moderate for both normal (0.71) and carious dentin (0.71). The hypothesis that detection of dentin reactions by SM and PLMQ would be influenced by the contrast quality of micrographic images was rejected. Dentin reactions were scored by SW, SD, PLMQ, and three types of microradiographic images with varying contrast qualities and each technique was compared against the one that resulted in the highest number of scores for each dentin reaction. Large differences resulted, mainly related to the detection of sclerotic dentin by both SW and SD, and normal and carious dentin by PLMQ. It is concluded that contrast-corrected microradiography should be preferred as the gold standard and SM and PLMQ should be avoided, but the relationship of PLMQ with dentin mineralization deserves further investigation.

Figure 1.. Typical aspects of dentin reactions in selected histological sites (labeled 1–4 with arrows) of natural occlusal caries (ICDAS II score 2).

Translucent dentin is shown in sites 1–3 from the SW image ( A) and in sites 1 and 2 from the SD image ( B). Site 1 appears as demineralized dentin in all types of MR images and as negatively birefringent (“carious dentin”) in PLMQ ( F). Site 2 appears as normal dentin in the NFNBC image ( C), as hypermineralized (sclerotic) in both NFBC ( D) and FBC ( E) images, and as negatively birefringent in PLMQ. Site 3 appears as carious (yellowish) dentin in the SD image ( B), as demineralized dentin in all types of MR images, and as positively birefringent (“normal”) in PLMQ. The appearance of site 4 is of normal dentin in all images. Bars = 1 mm.

Figure 2.. Effect sizes of comparisons between the “temporary gold standard” and other techniques on the detection of normal (black square + dashed line), carious (open circle + continuous line), and sclerotic (half-filled triangles + short dashed line) dentin.

Labels on the right are magnitudes of effect size in relation to the “temporary gold standard” only.

Figure 3.. Plot of normalized radiopacity against normalized translucency showing no correlation (black line = Pearson’s correlation fit; R ² = -0.013).

N = 80 histological sites.