Near‐IR and CP‐OCT imaging of suspected occlusal caries lesions

Abstract

Introduction Radiographic methods have poor sensitivity for occlusal lesions and by the time the lesions are radiolucent they have typically progressed deep into the dentin. New more sensitive imaging methods are needed to detect occlusal lesions. In this study, cross-polarization optical coherence tomography (CP-OCT) and near-IR imaging were used to image questionable occlusal lesions (QOC's) that were not visible on radiographs but had been scheduled for restoration on 30 test subjects. Methods Near-IR reflectance and transillumination probes incorporating a high definition InGaAs camera and near-IR broadband light sources were used to acquire images of the lesions before restoration. The reflectance probe utilized cross-polarization and operated at wavelengths from 1500–1700-nm where there is an increase in water absorption for higher contrast. The transillumination probe was operated at 1300-nm where the transparency of enamel is highest. Tomographic images (6×6×7 mm3) of the lesions were acquired using a high-speed swept-source CP-OCT system operating at 1300-nm before and after removal of the suspected lesion. Results Near-IR reflectance imaging at 1500–1700-nm yielded significantly higher contrast (p<0.05) of the demineralization in the occlusal grooves compared with visible reflectance imaging. Stains in the occlusal grooves greatly reduced the lesion contrast in the visible range yielding negative values. Only half of the 26 lesions analyzed showed the characteristic surface demineralization and increased reflectivity below the dentinal-enamel junction (DEJ) in 3D OCT images indicative of penetration of the lesion into the dentin. Conclusion This study demonstrates that near-IR imaging methods have great potential for improving the early diagnosis of occlusal lesions.

Multispectral near-infrared reflectance and transillumination imaging of occlusal carious lesions: variations in lesion contrast with lesion depth

“…3). This result is consistent with our findings in other OCT studies where we were able to measure the lateral spread of occlusal lesions when they reached the dentinoenamel junction [6, 9, 20]. …”

“…Stains in the occlusal grooves reduced the lesion contrast in the visible range yielding negative values on average. Additionally, only half of 26 lesions diagnosed as carious lesions and requiring restoration showed the characteristic surface demineralization and increased reflectivity below the dentinoenamel (DEJ) in 3D CP-OCT images indicative of lesion penetration into the dentin [6]. These results indicated that near infrared imaging holds great potential for the assessment of occlusal lesion depth, due to the high transparency of enamel and stain at λ=1300–1700-nm, which allows direct visualization and quantified measurements of enamel demineralization.…”

Detection of carious lesions utilizing depolarization imaging by polarization sensitive optical coherence tomography

“…11 Since then, several studies have shown the potential of PS-OCT to observe the internal structure and the remineralization of lesions, as well as an early detection of variously located caries. [12][13][14] Thereby, the occurring depolarization effect for linearly polarized incident light is usually evaluated by an intensity measurement of the perpendicular polarization state. 15 Complementary to the development of PS-OCT imaging for dental hard tissue, the assessment of depolarizing properties as a tissue specific contrast in ophthalmology led to the definition of the degree of polarization uniformity (DOPU) as a tool for retinal pigment epithelium segmentation.…”

Indocyanine green–assisted dental imaging in the first and second near‐infrared windows as compared with X‐ray imaging

“…The best practice for diagnosing insidious or hidden caries is to combine clinical observation and radiographic examination . However, X‐ray techniques fall short owing to the limitation of ionizing radiation and decreased specificity (about 50%) to occlusal insidious caries . Even from micro‐CT images, it is very difficult to find IEC, requiring hundreds of the slices taken at right angles.…”