Short-wave infrared optical imaging techniques for the assessment and quantification of dental disease
Creators: name: Sahyoun, Christine Charles
Publisher: name: No Publisher Supplied
Year: 2021

description: Periodontal disease and tooth decay are conditions that, if detected early enough, can be corrected or reversed. Visual inspection and radiography are the current standard detection methods for such conditions, and while cracks and caries can be identified with this methodology, dental lesions can only be detected through radiography once the disease has progressed significantly. There is a need for non-invasive, accurate, and quantitative assessment of both dental and periodontal tissue to allow for prompt diagnosis and subsequent treatment. Optical imaging approaches may offer improved assessments because they can provide full-field information from within the first few millimeters of tissue depth, which is appropriate for assessing both tooth layers (enamel and dentin) and gingival tissue. This dissertation is focused on developing optical techniques for quantitatively assessing dental tissue in a non-invasive, non-destructive manner for translation into clinical work. Optical coherence tomography (OCT) is a technique that uses infrared light to generate cross-sectional images of sub-surface tissue structure. While OCT has been investigated for dental applications, the elements of an OCT system can be configured differently and optimized for the requirements of specific applications, and there are several different commercially available OCT systems that can be used for dental applications. It had not yet been established which combination of system configurations and parameters is best for detection and quantification of enamel indications. Chapters 2 and 3 focus on applications of OCT for hard dental tissue assessment. Chapter 2 provides a detailed comparison of commercially available OCT systems using healthy enamel samples to demonstrate the performance of each system in relation to dental imaging. The systems in Chapter 2 were then utilized for the assessment and quantification of both artificial and natural white spot lesions in Chapter 3. Lesion formation, depth, and heterogeneity were assessed through OCT-established parameters to provide quantitative visualization of white spot lesions that could be used for both clinical identification of lesions and assessment of treatment efficacy. Spatial frequency domain imaging (SFDI) is another imaging modality that can be performed with infrared wavelengths to provide absolute quantification of tissue chromophore concentrations, including water. There appears to be only one report directly performing SFDI at short-wave infrared (SWIR) wavelengths for the extraction of water and lipid content, but this work is limited in wavelength range and utilizes measurements at many wavelengths in order to get accurate results. Optimization of both wavelength and spatial frequency choices needs to be conducted to lead to system simplification without sacrificing accuracy of chromophore extraction. Chapters 4 and 5 spotlight SWIR-SFDI for potential use in both oral and dental health evaluation. Chapter 4 details the creation of a SWIR-SFDI system and optimization of wavelength and spatial frequency selection for accurate extraction of water and lipid content using phantoms. Chapter 5 utilizes this system to provide a spatially resolved map of reduced scattering for the natural white spot lesion samples from Chapter 3, demonstrating the capability of the SWIR-SFDI system to provide quantitative assessment of hard dental tissue in addition to hydration evaluation.