Significance: It is not sufficient to detect caries lesions on tooth surfaces; it is also necessary to measure the activity of the lesions to determine if intervention is needed. Changes in the reflectivity of lesion areas during dehydration with forced air at short wavelength infrared (SWIR) wavelengths can be used to assess lesion activity since these changes represent the evaporation dynamics of water from the lesion.
Aim: The aim of this study is to develop new optical methods for assessing lesion activity on tooth surfaces utilizing the strong water absorption band near 1950-nm.
Approach: The time-resolved reflectivity of 20 active and arrested caries lesions on the surfaces of human extracted teeth was monitored at 1300 to 2000 nm using broadband light sources and an extended range InGaAs camera during drying with air.
Results: Multiple parameters representing the rate of change of the lesion reflectivity correlated with the presence of a highly mineralized outer surface zone indicative of lesion arrest measured with x-ray microtomography (microCT). Performance at 1950-nm was higher than for other wavelengths.
Conclusions: This study demonstrates that SWIR imaging near 1950-nm has great potential for the assessment of lesion activity.
Changes in the reflectivity of lesions on the proximal surfaces of extracted human teeth were measured at 1500-2340-nm and at 1950-nm as they were dried with air. An extended range tungsten-halogen lamp with a long pass filter (1500-2340-nm) and a broadband ASE source centered near the peak of the water-absorption band at 1950-nm were used as light sources and an extended range InGaAs camera (1000-2340-nm) was used to acquire reflected light images as the samples were dried with air. SWIR light at 1950-nm yields extremely high contrast of demineralization and appears to be the optimum wavelength for the assessment of lesion activity on tooth coronal surfaces.
This study investigated the utility of using OCT to monitor SDF application over time. Twenty dentin blocks each with 5 windows were exposed to a demineralization solution to produce carious lesions. Treatment windows included sound, sound+SDF, lesion, lesion+SDF, lesion+SDF+SDF. Lesion depth, mean reflectivity over the lesion depth and optical penetration through the lesions were monitored with OCT for 12 weeks. OCT was able to show changes in the reflectivity and optical penetration in demineralized and sound dentin after SDF application over time. Such changes can potentially be monitored to determine if and when re-application of SDF is needed.
Significance: We have developed a clinical probe capable of acquiring near-simultaneous short-wavelength infrared (SWIR) reflectance and occlusal transillumination images of lesions on tooth proximal and occlusal surfaces. We hypothesize that dual images will aid in differentiating between shallow and deep occlusal lesions and reduce the potential of false positives (FPs).
Aim: The aim of this study was to test the performance of the dual reflectance and occlusal transillumination probe on extracted teeth prior to commencing clinical studies.
Approach: The dual probe was 3D printed and the imaging system uses an InGaAs camera and broadband superluminescent diode light sources that emit broadband light at 1300 nm for occlusal transillumination and 1600-nm light for cross-polarization reflectance. The diagnostic performance of the dual probe was assessed using 120 extracted teeth with approximal and occlusal lesions. Reflectance and transillumination images were fused into single images to enhance the contrast between sound and lesion areas. The lesion contrast in both modes did not increase significantly with either the lesion depth or the distance from the occlusal surface for approximal lesions. In addition, the diagnostic performance of radiography, the individual reflectance and transillumination images, dual images, and fused images were compared using micro-computed tomography as the gold standard.
Results: Reflectance imaging at 1600 nm yielded the highest diagnostic accuracy for lesions on both occlusal and proximal surfaces while radiography yielded the lowest number of FPs.
Conclusion: This study demonstrates that simultaneous acquisition of both reflectance and transillumination SWIR images is possible with a single clinical device.
Internal adaptation of adhesive restorations affects their longevity. In a clinical setting, the dentists use visual and tactile examination to evaluate marginal adaptation, while radiographs provide somewhat reliable information about adaptation or secondary caries present. For class V restorations located on the vestibular (buccal) surfaces, none of the tools available can provide any information about the internal adaptation or the presence of secondary caries. OCT has been proven to be a useful tool for non-destructive assessment of internal adaptation of adhesive restorations. This paper is evaluating the use of a new high-resolution handheld OCT prototype with a pen-shaped intraoral tip and an imaging depth of 8mm to examine the internal adaptation and the presence of demineralization under resin restorations on the vestibular dentin surface. The Axsun OCT system helped evaluate the internal adaptation of composite restorations, differentiate between healthy and demineralised dentin, adhesive, and restoration layers. OCT provided a unique visualization and characterization of internal structures as well as non-contact assessment of marginal adaptation.
Dental caries is one of the most important oral global health burdens. Even though the scientific community has a good understanding of its etiology, almost 100% of the population still present dental caries in one form or another. Different reasons such as lack of oral health education, symptom-driven consultations and late caries detection may be considered as the main explanations. Recently, new noninvasive therapies showed an important protective effect against caries progression. These new treatment options can be mainly applied in case of non cavitated lesions, thus the need for early caries detection becomes crucial. With novel near infrared technologies, early enamel lesions can be detected and monitored over time to provide information on the lesions’ activity and the caries risk level. The long-term monitoring of early lesions- treated or not - is now possible with near infrared caries detection tools. With no ionizing radiation required, frequent imaging of the lesions is possible for high risk patients. Near infrared early caries detection can improve the success rate of noninvasive preventive and therapeutic measures, while providing the opportunity to monitor carious lesions in their early stages and to offer a large window of opportunity for early intervention, when necessary.
Transparent remineralized surface zones found on natural caries lesions may reduce the permeability to water and plaque generated acids. Near-IR (NIR) reflectance imaging coupled with dehydration can be used to measure changes in the fluid permeability of lesions in enamel and dentin. Previous work demonstrated a negative association between the surface zone thickness and the rate of dehydration in simulated enamel lesions. In this study, the rates of dehydration and thickness of transparent surface layer of coronal lesions of extracted teeth were measured and correlated. Reflectance imaging at NIR wavelengths from 1695-1750 nm, which coincides with higher water absorption and manifests the greatest sensitivity to contrast changes during dehydration measurements, was used to image these enamel lesions. The remineralized surface layer thickness was determined using optical coherence tomography (OCT).
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