Improved methods are needed to assess the structure and activity of lesions on root surfaces in order to improve clinical decision making. Conventional visual and tactile methods for assessing lesion activity are not reliable, and the clinician is often unable to evaluate if the lesion is progressing or has remineralized. An important marker of an arrested lesion is a highly mineralized surface zone that forms when mineral is deposited in the outer layer of the lesion. In vitro studies have shown that a mineralized surface zone influences the kinetics of water evaporation and the surface temperature while drying. Temperature changes can be monitored by measuring the thermal emission with thermal imaging. Studies have also shown that the depth and severity of demineralization and the thickness of the highly mineralized transparent surface zone on arrested lesions can be measured nondestructively with optical coherence tomography (OCT). Thermal imaging at 8-µm to 13-µm wavelengths was completed on 30 test subjects with a suspected active root caries lesion by monitoring thermal emission from the tooth surfaces during 30 s of air drying. Lesions were also evaluated using cross-polarization OCT (CP-OCT) during lesion dehydration to identify transparent surface zones indicative of arrested lesions and determine if shrinkage occurred during drying. The overall thermal emission recorded during drying was significantly different ( P < 0.001) when comparing sound tooth surfaces, lesion areas identified as arrested, and lesion areas identified as active, demonstrating that thermal imaging is a promising approach for the clinical assessment of lesion activity on root surfaces. Ten of the lesions in this study had distinct areas with transparent surface zones that were visible in CP-OCT images. Shrinkage was detected with CP-OCT during drying for 12 lesions. This study confirms that these novel approaches for assessing lesion activity on root surfaces can be implemented in vivo.

This clinical study tested crosspolarization optical coherence tomography (CP-OCT) monitoring of erosive tooth wear (ETW). Twenty participants completed a 14-day/arm, 3-arm crossover study simulating different ETW severities. Participants received two enamel specimens (per arm) and were randomized to: severe (s-ETW, lemon juice/pH:2.5/4.25% wt/vol citric acid), moderate (m-ETW, grapefruit juice/pH:3.5/1.03%wt/vol citric acid), and non-ETW (water).Enamel thickness was measured with CP-OCT (day[D] 0, 7, 14) and microcomputed tomography (μ-CT; D14). Enamel surface loss was determined with CP-OCT and optical profilometry (OP; D7, D14). CP-OCT showed higher enamel surface loss for D14 than D7 for m-ETW (P = .009) and s-ETW

The identification of root caries and calculus on tooth roots is of increasing importance with our aging population. Exposed root surfaces are often impacted by erosion, abrasion, calculus and staining which can make the identification and management of caries challenging. Identification of dental calculus on root surfaces and verification of its removal is also important for patient education and to decrease susceptibility to caries and periodontal disease. The objective of this study was to determine how the contrast of root caries lesions and dental calculus varies with wavelength in the visible to near-infrared. The contrast of suspected root caries lesions and dental calculus on 30 extracted teeth was measured using cross-polarization reflectance measurements at wavelengths from 400 to 2350 nm. Significantly higher (P < 0.05) lesion contrast was measured at wavelengths greater than 1460 nm. Stains interfered significantly at wavelengths less than 850 nm yielding non-diagnostic contrast for root caries lesions. We postulate that the high absorption of water at longer wavelengths reduced the light scattering from the surrounding and underlying normal dentin, thus increasing the lesion contrast. This study indicates that wavelengths beyond 1400 nm are advantageous for imaging calculus and caries lesions on root surfaces due to the high contrast and lack of interference from stain.

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