Al-Khuwaitem, Rawan Waleed; (2019) The Use of Optical Coherence Tomography as a Diagnostic Tool for Dental Caries. Doctoral thesis (D.Dent), UCL (University College London).

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Abstract

Dental caries is one of the most common human diseases, 60-90% of school children world-wide have dental cavities. Severity can vary, from early demineralisation, which preventive measures can improve, to cavitation, leading to fillings. Different diagnostic tools are available, such as clinical examination, radiographic investigation and Enhanced Visual examination/In-ternational Caries Detection and Assessment System (ICDAS). To date, there is no universal diagnostic tool that can be used to detect carious lesions at the very early stages. Optical Coherence Tomography (OCT) is a non-invasive and ionising radiation free technique that has been used in dentistry, but not to diagnose caries. // The aim of this research was to investigate the use of OCT imaging in dentistry as a routine, and adjunct clinical diagnostic tool for dental caries, by developing standardised markers for each ICDAS score, and to compare the results with conventional clinical methods i.e. radio-graphs and ICDAS. In addition, markers in the OCT scan and scattering profile intensity plots for both sound and carious affected teeth were determined, to aid diagnosis. // All specimens were collected from patients undergoing dental treatment at Eastman Dental Hospital. Extracted human primary and permanent teeth (N>180) with varying caries severity were collected under ethical approval, after obtaining informed consent according to the inclu-sion and exclusion criteria. Photographic and radiographic images of tooth samples were taken and categorised according to the ICDAS system. Samples were then imaged using OCT (VivoSight OCT Scanner) with each lesion scanned separately (N>200). The scattering inten-sity profiles were plotted. In healthy samples, OCT B-scans showed a homogenous pattern of scattering intensity throughout enamel structure indicating healthy structure while in carious teeth, a non-homogenous scattering intensity was observed indicating changes in enamel structure. // Different scattering intensity profiles for each ICDAS score were observed, and empirical markers were developed for each score. This led to establishing scattering fingerprints for each type of ICDAS lesion. A multi-assessor’s analysis, followed by a kappa analysis, was carried to evaluate the selectivity and accuracy of the makers. The results showed moderate to substantial strength of agreement in both intra-rater and inter-rater reliability. // In conclusion, OCT has been shown to be a safe, useful, reliable and non-destructive tech-nique that can investigate the internal structure by measuring the back-scattered light from enamel and dentine. OCT provides an understanding of the lesion in terms of depth and ex-tent, therefore helping in predicting the lesion’s prognosis, which is not found in conventional methods. In addition, OCT helps to differentiate between carious and sound teeth, and addi-tionally between different ICDAS scores. The definition of specific scattering markers for each type of caries lesions will enable us to bring this technique one-step closer to the clinic.

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