Optical Coherence Tomography in Dentistry – An Updated Review

ISSN: 2581-5989 PubMed - National Library of Medicine - ID: 101738774 International Journal of Dental Science and Innovative Research (IJDSIR) IJDSIR : Dental Publication Service Available Online at: www.ijdsir.com Volume – 4, Issue – 3, May - 2021, Page No. : 459 - 475 Optical Coherence Tomography in Dentistry – An Updated Review 1 Sowmya Hemanthakumar, Assistant Professor, Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College and Hospital 2 P. Mahesh Kumar, Associate Professor, Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College and Hospital 3 K. Saraswathi Gopal, Professor and Head of the Department, Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College and Hospital Corresponding Author: Sowmya Hemanthakumar, Assistant Professor, Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College and Hospital Citation of this Article: Sowmya Hemanthakumar, P. Mahesh Kumar, K. Saraswathi Gopal,“Optical Coherence Tomography in Dentistry – An Updated Review”, IJDSIR- May - 2021, Vol. – 4, Issue - 3, P. No. 459 – 475. Copyright: © 2021, Sowmya Hemanthakumar, et al. This is an open access journal and article distributed under the terms of the creative commons attribution noncommercial License. Which allows others to remix, tweak, and build upon the work non commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms. Type of Publication: Review Article Abstract Introduction Optical Coherence Tomography (OCT) is a new Optical coherence tomography (OCT) is an emerging technology for performing high-resolution cross sectional diagnostic method for cross-sectional imaging of internal imaging. OCT is analogous to ultrasound imaging, except biological structures. OCT helps visualize differences in that it uses light instead of sound. OCT can provide cross tissue optical properties, which include the effects of both sectional images of tissue structure on the micron scale in optical absorption, and scattering.1 The general principle situ and in real time. of using reflections to create the images is the same for It is based on low coherence (long OCT and ultrasound but the methods for detecting these wavelength) which penetrates into the scattering media reflections are different. The use of light as the medium in (e.g.: oral tissues) and capture sub-micrometer resolution. OCT gives it the advantage of being non contact for the This paper reviews the understanding of the OCT, its patient.2 basics, systems & setup, uses, limitations with the focus of As light is faster than sound, the time delays between it as a diagnostic imaging tool for oral lesions. reflections from different layers cannot be measured Keywords: Optical Coherence Tomography, Resolution, directly, the differences would be on the order of femto Ultrasound, Interferometry, wavelength. seconds, hence, OCT uses low-coherence interferometry interferometry, employs near infrared light to see the time difference corresponding to the distances between structures3. Initially, OCT was developed to Corresponding Author: Sowmya Hemanthakumar, ijdsir, Volume – 4 Issue - 3, Page No. 459 - 475 Page 459 Conflicts of Interest: Nil OCT may provide a solution to these problems. Dental been used to image non transparent tissues4. This added OCT detects qualitative and quantitative morphological advantage has been utilised in imaging the oral cavity as changes of dental hard and soft tissues in vivo. they have both transparent and non transparent tissues. Furthermore, OCT can also be used for early diagnosis of Moreover, oral cavity is particularly well suited for OCT dental diseases, including caries, periodontal disease and imaging oral cancer, because of the excellent spatial resolution. because they are easily accessible for interrogation by the fibre-optic OCT device. 5 Early detection and treatment can increase the survival The non-invasive nature of this imaging modality coupled rates of teeth and patients. Three-dimensional imaging with (i) a penetration depth of 2–3 mm, (ii) high resolution ability is another advantage of dental OCT. It helps (5–15μm), real-time image viewing, and (iii) capability for clinicians to locate problems in soft and hard tissues more cross sectional as well as 3D tomographic images, provide accurately and rapidly.10 excellent prerequisites for in vivo oral screening and This review paper discusses the development of dental 6 diagnosis. OCT. The applications of OCT in dentistry by imaging Application of OCT in dentistry has become very popular. oral tissue, tooth decay, periodontal disease and oral The first in vitro images of dental hard and soft tissues in a cancer are also reviewed. porcine model were reported in 1998. Later, the in vivo Historical Perspective 7 imaging of human dental tissue was presented . The oral The concept of using light and optics to image biological cavity consists of three main parts: (1) hard tissue, tissues was first proposed by Duguay in 197111. Fujimoto including tooth and alveolar bone, (2) soft tissue, in 1989 imaged the retina of the eye using OCT. Huang et including mucosa and gingiva tissues, and (3) periodontal al., in 1991 did extensive work on the usage of OCT for 8 tissues . The traditional diagnosis of caries is based on imaging retina, optic nerve head structure and coronary examination using dental exploration and radiographs. arteries. Fercher et al presented the first in vivo OCT The the images in 1993. In 1994, Carl Zeiss Meditec, Inc (Dublin, examination of periodontal probes. The poor sensitivity California) patented OCT. The first commercially and reliability of periodontal probing make it difficult for available OCT, called OCT 1000, was marketed in 1996 dentists to monitor the progression of periodontal and then OCT 2000 in the year 2000. Otis et al in 2000 diagnosis of periodontal disease needs 9 destruction and the treatment outcome . Radiography may proposed the OCT imaging for dental applications. be the most popular diagnostic tool recently. However, Wojtkowski et al., (2001) presented the first in vivo radiography provides only two-dimensional images. The spectral-domain (SD)-OCT scans. In 2002, US Food and caries or bone structure on the buccal and lingual sides of Drug Administration (FDA) approved the SD-OCT teeth may be superimposed with tooth structures or normal systems for clinical use12. anatomic Principle of OCT structures. The radiation exposure of concern. Optical coherence tomography and US imaging has most Furthermore, early detection of caries, periodontal disease often been compared. OCT and US imaging employ and oral cancer is quite difficult with clinical examination backscattered signals reflected from different layers in the or radiographs. tissue to reconstruct structural images, with the US radiographic techniques is © 2021 IJDSIR, All Rights Reserved also a great Page image the transparent tissue, such as eye, recently it has 460 Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) imaging quantifying sound waves rather than light. The analyzing interference of the recombined light waves resulting optical coherence tomography image is a 2D engenders the image. CS images of tissues are constructed representation of the optical reflection in a tissue in authentic time, at near histologic resolution of 10 mm. sample. 13,14 The 10 mm resolution of OCT displays depth, thickness, peripheral margins, and histopathological appearances of the tissues in-vivo. Thus, OCT ameliorates on subsisting clinical capabilities, particularly for the identification of biopsy sites for monitoring of lesions, and for screening of a high-risk population. With 1-3 mm of tissue perforation depth, the imaging range of OCT diagnostics is opportune for the oral mucosa. The normal human oral mucosa is very delicate, ranging from 0.2 mm to 1 mm in thickness. Different scanning procedures in OCT imaging are axial scans withal called as A-scan, longitudinal scan or B-scan, En-face scans or T-scans and transverse slice scansl called as C-scan.12-16 Interferometry is the main principle of OCT. It is an evolving imaging modality that cumulates interferometry with low-coherence light to engender high-resolution tissue imaging. CS in-vivo images were obtained utilizing an OCT contrivance consisting of a Michelson interferometer, light source (1.3 μm broadband), and a handheld fiber optic imaging probe. Image pixel has reached the resolution of 10 μm. Broadband laser light waves are emitted from a source (Ws) and directed toward Figure 2 a beam splitter. One wave from the beam splitter is sent to the tissue sample (Wt) and the other toward a reference mirror (Wr). After the two beams reflect off the reference mirror and tissue sample surfaces at varying depths, they which will further analyze the beams (Figure 2). The © 2021 IJDSIR, All Rights Reserved Page and together are directed to the photo detector (Wp), 461 are directed toward the beam splitter, where they merge Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) It scans in a transverse direction and is actually a collection of many T scans transversally. It is particularly useful in imaging the retina. Figure 4: Relative orientation of the axial scan (A-scan), longitudinal slice (B-scan), x-y (transverse) scan (T-scan) the engine performing the imaging and its application. Main Characteristics Of Oct12-16  600 to 2,000 nm, where the main constituents of the A-scan or Axial scan It measures the depth of the object being scanned. The data obtained is one dimensional. tissue, water, pigments exhibit low absorption  of different A-Scans, taken linearly across the object and should be smaller  best achieved by single scattered photons rather than and lateral aspect of the object can be assessed. multiple photons because, as the number of photons T-Scan or en-face scans transversally while maintaining a fixed reference point. increases, the event loses the phase information  weak signal in the object arm, backscattered or lateral direction. It is the most popular modality to record transmitted through the tissue, is amplified by the the occlusion. It accurately records the force exerted, time helps in determining the length of bite, the time and force with which the teeth occlude. C-Scan or Coronal scan Photodetection at the interferometer output involves multiplication of the two optical waves, therefore, the This reference point could either be angulated or in a taken and amount of occlusal surface in contact. This scan A strict phase relationship is required between the interfering waves for interference to take place. This is following this in a transverse direction. Thus both depth It is produced by a beam which scans the object To achieve high depth resolution, the optical spectrum line width should be wider and the coherence length B-Scan It is similar to ultrasound B scan. It is actually a collection The wavelengths utilized in OCT imaging lies within strong signal in the reference arm.  This explains the higher sensitivity of OCT when compared with confocal microscopy, which for instance in skin can produce images only to a depth of 0.5 mm © 2021 IJDSIR, All Rights Reserved 462 There are three main scanning procedures depending on and en-face or transverse slice (C-scan). Page Scanning modes in OCT imaging: 17 Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR)  OCT is built around a confocal microscope, hence, the Table 1 shows a comparison between dental OCT and transverse resolution is determined by diffraction other dental diagnostic methods used today.19-24 Dental OCT imaging is considered safer as the power of Radiography 1. Low cost 1. Radiative the source in the assuming 8 hours of continuous 2.Broad 2.Poor exposure, when compared it is thousand times less than measurement range resolution the current systems falls far below the American National 3. Standards Institute (ANSI) standard for tissue damage. image   The ANSI threshold for skin damage using a source Only 1.Broad 1.No with a 1.3 mm wavelength is 96 mW, criterion. measurement range image Live 2. subsurface images at Dental-CT near-microscopic resolution. 3-D spatial 2-D real-time image 2. Radiative reconstruction 3.Poor spatial  Instant, direct imaging of tissue morphology.  No preparation of the sample or subject. Intraoral 1. Low cost 1. Only surface  No contact with the patient Digital camera 2.Non-radiative information  No ionizing radiation Periodontal 1. Low cost 1.Low probe 2.Broad sensitivity measurement range 2. No image resolution 3. Invasive OCT 1. High spatial 1.Limited resolution penetration 2.Real-time image depth 3. 3-D and image scanning range reconstruction is available Raman 1.High sensitivity spectroscopy 2.Responses mineral chemical Figure 5 vitro to measurement and 2. Expensive 3. No image concentrations fluorescence detection spectrometer 2.Responses chemical concentrations time 1.Lack of diagnostic to consistency and 2.No image 463 1.Real Page Laser bacteria © 2021 IJDSIR, All Rights Reserved 1.In Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) Types of OCT18 submucosa and muscle layer are clearly visible (A: There are two main types of OCT Anterior view; B: Lateral view; e: epithelium; b: basement  Time Domain OCT (TDOCT) membrane; m: mucosa). From: Jung WG, Zhang J, Chung  Spectral Domain OCT (SDOCT) JR, Wilder-Smith P, Brenner M, Nelson JS, Chen Z  Functional OCT (2005). Advances in oral cancer detection using optical  Sensitive OCT coherence tomography.  Polarisation Sensitive OCT  Differential Absorption OCT  Doppler OCT  En-Face OCT or Full-Field OCT Applications of Dental OCT Early OCT studies focused mainly on the topics of dental soft and hard tissue morphology because of the limitation of system size and light source manufacture technology. Nowadays, OCT is not only an “imaging tool” but also an important and non-invasive method could be applied in Figure 7: Handheld probe for oral OCT Normal tooth structure advanced diagnosis problems such as tooth decay, periodontal disease and oral cancer. The use of OCT in dentistry is further simplified with the introduction of handy dental probes where diagnosis can be done on the chair side.25,26 Figure 8: Reprinted Laboratory, 2001 from: Optical Engineering 27 wherein OCT could have important applications. system (Imalux Corp., Cleveland, OH, USA). (b) 1. Dental X-rays considerably underestimate caries lesion Photograph of intra-oral fiberoptic probe (Reproduced size and are not sensitive enough. By the time a lesion is with permission: Jun Zhang and Zhongping Chen for 3D visible on radiographs, the demineralization has extended imaging). (c) In the 3D reconstructed OCT images of to or beyond the middle third of the dentin. healthy hamster cheek pouch mucosa, the surface 2. Tooth cracks have been a diagnostic challenge because squamous of the difficulty in locating the fracture lines of an keratinized epithelium, © 2021 IJDSIR, All Rights Reserved and underlying Page Figure 6: (a) Intra-oral imaging using the Imalux™ OCT 464 In general, there are different types of clinical scenarios Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) incomplete fracture. Early detection and diagnosis are diagnosing primary caries are highly invasive and less important to limit crack growth. reliable in the detection of early caries. 3. Clinical assessments of margin quality for intraoral In such instances, OCT appears to be a promising restorations are routinely carried out in dental practice; technique by providing information about the extent of the however, the replacement of existing restorations and the carious lesion and it can also differentiate between stain, decisions related to treatment planning are very subjective enamel dysplasia and active decay. Moreover, OCT can In Caries Diagnosis: 28 image through water, saliva and plaque and can record Caries is an important dental care issue. Caries has high microstructural changes underneath any materials for prevalence and wide distribution among ages. The World marginal Health Organization (WHO) revealed that dental caries is fractures, voids and early stages of demineralization still a major public health problem globally and major beneath occlusal sealants or orthodontic composite public health problem in most high-income countries. The brackets. enamel displays powerful birefringence and there is OCT imaging can be helpful in determining the anisotropic propagation of light via dentinal tubules. progression of decay and the treatment outcome by having Baumgartner et al. presented the first polarization resolved a vital role in evaluation of remineralization of the tooth images of dental caries. Wang et al. measured the following fluoride application or in case of arrested caries. birefringence in dentin and enamel and suggested that the This is based on the hypotheses that the restoration of enamel rods acted as waveguides [46]. PS-OCT is suitable mineral volume would result in a measurable decrease in for the detection of secondary caries, because the the depth-resolved reflectivity. Jones and Fried in 2006 scattering properties of restorative materials and dental conducted a study to test the above stated hypotheses by hard tissue have marked differences. measuring the optical changes in artificially caries induced integrity, bonding interphase, structural and remineralized human tooth specimens using PS-OCT. The authors concluded that the mineral volume changes before and after remineralization can be measured accurately on the basis of the optical reflectivity of the lesion. Figure 9 Presently, diagnoses of carious lesions are mainly through the latter known for its high sensitivity and specificity for © 2021 IJDSIR, All Rights Reserved section of pulp exposure. (B) The pulp and dentin were 465 former does not detect the non-cavitated lesions, whereas Figure 10: Site of pulp exposure. (A) Histologic cross- Page visual and radiographic examination. Unfortunately, the Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) clearly delineated in the OCT image (P: pulp; D: dentin; PE: pulp exposure) Endodontics:29 In case of root canal therapy, understanding the complexity of the root canals plays a vital role in its outcome. The OCT outsmarts conventional endoscopes through its small diameter and increased flexibility of the probe. In addition, OCT imaging does not require dry root canal and they provide a characterised microscopic detailed image through the surrounding root canal circumferential from dentin to cementum. Such measurements are capable of indicating the exact thickness of the dentinal wall and can aid inFigure 11: Oval canals and uncleaned fins at 7 mm from determination of minimal dentin thickness to prevent root canalthe apex revealed by histology (H) and optical coherence over preparation and possible perforation of canal walls. tomography (O). Oval canals (A) and canal fins (B). Intraoperatively, OCT imaging of root canals can indicate Fracture lines in tooth uncleaned fins, transportation of the canals, hidden Fracture lines (FL) in enamel, zoom (occlusal overloaded accessory canals and measurement of the apex. Shemesh anterior tooth, with a normal crown morphology): 18 et al in 2007 evaluated OCT’s ability to image root canal degree in air if 18 degrees, this is not zoom, for the walls following endodontic preparation and correlated review you should give the size in mm these images to histological sections. The authors concluded that OCT was reliable for imaging root canals and the dentinal wall in a nondestructive manner. Determining the presence of vertical root fractures pose a challenge to the clinician and a threat to the tooth’s prognosis, both during root canal therapy and postoperatively. Diagnosis of such fractures is difficult and mostly subjective, involving direct visualisation, bite tests, staining, transillumination, probing and radiographs. Radiographs are limited and can reveal a vertical root fracture only if the X-ray beam is parallel to the line of fracture. A controlled blind OCT endodontic study concluded that OCT is a valuable tool for imaging and identifying vertical root fractures and detecting the Figure 12: Reprinted from :Carmen Todea1, 2010 © 2021 IJDSIR, All Rights Reserved Page 466 fracture’s location along the root. Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) The images obtained through OCT were correlated with histological sections and clinical probing. The authors observed that the images generated using the 1,310 nm wavelength systems were significantly better as compared with those images obtained from 850 nm system. The authors opined that the improvement in the image quality of 1,310 nm wavelength system was primarily due to the two-fold increase in its imaging depth and also due to its larger numerical aperture. The authors concluded that the OCT can provide excellent microleakage formation beneath resin material (G: gingival; RBC: resin based composite; E: enamel; D: dentin; DEJ: dental enamel junction) Periodontics:30 The microanatomy of periodontium and its soft tissue density does not allow routine imaging. Hence, the current periodontal diagnosis is completely based on clinical examination and evaluation of alveolar bony changes which are seen only after the progression of the disease. Otis et al in 1998 evaluated the accuracy of OCT for taking in vitro images of periodontal structures using an animal model. The authors found that the OCT images were comparable with the histopathology. However, the observations were limited because of the poor signal-to noise ratios associated with the bulk optics used. The images produced were thus merely topographical maps corresponding to characteristic reflections from the interface between tissue and air. With the promising observations noted in the previous study Otis et al in 1998 performed a study with porcine mandibles using two prototypes dental OCT systems (an 850 nm wavelength, 700 mW system with a relatively low numerical aperture of 0.03 and a 1,310 nm wavelength, 140 mW system with a higher numerical aperture of 0.20). © 2021 IJDSIR, All Rights Reserved images of the periodontal soft tissue attachment, contour, thickness and depth of the periodontal pockets in vitro. At the outset, the authors hypothesized that another important mechanism that can improve the quality of the OCT image is the composition of tissue that is imaged. Hence, it is likely that in vivo OCT images will have improved contrast when compared to the nonvital specimens used in the present study. This is based on the theory proposed by Brezinski et al that the strong contrast between cardiac muscle and adjacent adipose tissue on OCT images found in his study may be attributable to their water content. Similarly, it is conceivable that sulcular fluid will enhance contrast for imaging periodontal tissues in vivo. Variations in the tissue fluid resulting from periodontal diseases may provide differences in contrast important for clinical imaging. To evaluate the efficacy of OCT in vivo imaging of periodontium, Otis et al in 2000 performed a study among healthy adults with no clinical evidence of gingivitis or periodontal disease. The dental OCT system consisted of 140 μW, 1,310 nm superluminescent diode light source which can detect up to 70 femtowatts of reflected light. It has an imaging depth of approximately 3 mm, with an image acquisition time of 45 seconds. The authors concluded that the in vivo dental OCT images clearly depicted periodontal tissue contour, sulcular depth and 467 Class V restoration in the central incisor. Arrow shows Page Figure 13: Photogragh (A) and SS-OCT image (B) of Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) connective tissue attachment. In addition, the authors fractures in several fixed partial dentures using two single stated that as OCT reveals microstructural detail of the mode directional couplers with a super luminescent diode periodontal soft tissues, it offers the potential for as the source at 1,300 nm employing enface scanning identifying active periodontal disease before significant procedure. Here, the image acquisition was done by alveolar bone loss occurs. obtaining both C-scans as well as B-scan images. The resultant images showed voids of different sizes and shapes between the material interfaces at different depths. Figure 14: Images of a periodontal ligament. (A) Radiograph. (B) OCT. (C) Logging OCT images; the boundary of each tissue can be identified more clearly. Figure 15: OCT image of subgingival calculus. (A) Subgingival calculus without coverage of gingiva. (B) Subgingival calculus covered with gingival. Figure 16: Marginal adaptation of an empress veneer on which are bridged or bonded together, such as acrylics, ceramics, polymers, composites and metals. They are liable to fracture due to a variation in their physical and mechanical properties and masticatory load. Currently, several methods are employed for evaluation of the micro leakage, such as bacterial penetration, fluid transport, clarification electrochemical and penetration methods and of gas radioisotopes, chromatography. However, none of them are found be effective and can be considered standard. Sinuescu et al in 2008 performed a study to evaluate the capability of OCT in detection and analysis of possible the proximal area Orthodontics Can be used for evaluating the demineralized white lesions surrounding orthodontic brackets, and for determining tooth movement under light orthodontic forces. OCT investigation provides information on the microleakage of the bracket’s bonding , gaps are also assessed along the bracket base. A lack of adhesive material on the side of the bracket can be seen too. Uses in the soft tissue pathologies:32 Oral mucosa : To operate OCT imaging of oral mucosa, a compact, dual wavelength, fiber-based superluminescent diodes operating at 830 nm (Dl=25 nm) and 1280 nm (Dl =50 nm) served as the short coherent length light source, © 2021 IJDSIR, All Rights Reserved 468 The dental prosthesis are integrated of various materials Page Prosthodontics:31 Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) producing 1.5 mW and 0.5 mW powers to the object difficult to distinguish the lamina propria and submucosa respectively. The indepth resolution of the OCT scanner from EP. OCT imaging also reveals blood vessels and was 13 microns (830 nm) and 17 microns(1280 nm). glands in LP and submucosa because their optical 1. Masticatory Mucosa (gingival and hard palate mucosa) properties differ significantly from their environment A characteristic feature of keratinized regions in the oral (fibrous connective tissue). cavity is the presence of relatively high connective tissue Malignant and potentially malignant condition:33,34 papillae projecting into the overlying epithelium. The 200 OCT can perceive early transmutations in malignant and μm thick region beneath the squamous epithelium is the premalignant changes like loss of epithelial stratification, lamina propria (LP). The papillae of the LP within the hyperkeratosis, epithelial down growth, disruption of the epithelium contain strong basement membrane. bundles of collagen fibers which are tightly interlaced and Accounting for 96% of all oral cancers, squamous cell woven into the periosteum45 (bone covering tissue). carcinoma (SCC) is usually preceded by dysplasia In the OCT scan, a distinct boundary between the LP and presenting as white epithelial lesions on the oral mucosa the periosteum is visible. The total depth of OCT imaging (leucoplakia). in the gingival mucosa is 600-650μm. erythroplakias carry a risk of malignant conversion of 2. Lining Mucosa (alveolar, soft palate, labial, and buccal 90%19. Tumour detection is complicated by a tendency mucosa, as well as the mucosa of the mouth floor and the toward field cancerization, leading to multi centric lesions. ventral surface of the tongue) This high-resolution optical technique permits minimally In OCT image of vestibular alveolar mucosa, the invasive imaging of near-surface abnormalities in complex epithelium (EP) is seen as a straight, transparent layer tissues, having a penetration depth of 1-2 mm. This ~150 μm in thickness. The LP, seen as the brightly permits in vivo noninvasive imaging of the macroscopic backscattering (500 μm thick) strip in the OCT scan, is a characteristics of epithelial and subepithelial structures, fibrous connective tissue structure and is separated from including: the EP by a basement membrane. It also contains muscle appearance and peripheral margins. Oral mucosa is very fibers and blood vessels which weakly backscatter and thin, ranging from 0,2 to 1 mm. appear as dark structures in the scan above the darker, In a study of Wilder-Smith, 50 patients were evaluated, bony attachment. examined and photographed with white or red intra-oral 3. Specialized Mucosa (lips, dorsum of the tongue) lesions. The imaging was carried out along the long axis at OCT images of those parts where the epithelium the center of each lesion using either a fiber optic high- evidences gingiva, resolution 3D OCT probe with a scan length of up to 10 vermillion border of the lip, buccal zona intermedia, mm or a commercially available 2D probe with a scan dorsal surface of the tongue, hard palate) substantially length of 2 mm Niris TM OCT imaging system by Imalux differ from images of those parts where EP evidences low (Cleveland, OH). Contra lateral healthy tissues were or no keratinization in its normal state (alveolar mucosa, scanned in a similar fashion. The acquisition required labial mucosa, floor of the mouth, and soft palate). approximately 5-180 seconds per 3D scanning and 1,5 (marginal Keratinization may reduce the contrast and makes it © 2021 IJDSIR, All Rights Reserved and in thickness, the form of histopatological 469 keratinisation depth lesions Page high Dysplastic Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) seconds for 2D scanning, totalling less than 15 minutes for each patient. In the OCT images, epithelium, lamina propria, and basement membrane are clearly visible. The OCT image of a dysplastic lesion parallels histopathological status, showing epithelial thickening, loss of stratification in lower epithelial strata, epithelial down growth, and loss of epithelial stratification as compared to healthy oral mucosa. The epithelium is highly variable in thickness, with areas of erosion and invasion into the sub epithelial layers. The basement membrane is not visible as a coherent landmark. OCT image is rapid, unproblematic and well received by all patients. In another study of 97 patients utilizing OCT imaging to detect neoplasia in the oral cavity by Tsai et al. in 2009, Figure 17: Histological images of the (a) normal, (b) MiD, their results revealed that the an important criteria for (c) MoD, (d) ES-SCC, and (e) WD-SCC samples high-grade dysplasia/carcinoma in-situ was the lack of a layered structural pattern. Diagnosis predicated by this method for dysplastic/malignant versus benign/reactive conditions achieved a sensitivity and specificity of 83% and 98%, respectively, and by 0.76 as an inter-observer accident value. Their study concluded that OCT, had high sensitivity and specificity along with a good inter-observer Figure 18. SS-OCT scanned images of the (a) normal acquiescent, is a promising imaging modality for non- control and biopsied oral (b) MiD, (c) MoD, (d) ES-SCC, invasive evaluation of tissue sites, suspected with high- and (e) WD-SCC lesions. Their histological images were grade dysplasia or/ and cancer.8 Lee et al. in 2009 had shown in Figure 17(a–e) diagnosed the OSMF with OCT. Compared with the Cancer therapy-induced mucositis: 35 conventional method of quantifying maximum mouth OCT has manifestated its benefit in the detection of opening, the utilization of the proposed OCT scanning transmutations in cancer therapy-induced mucositis. results can be a more accurate technique for OSF Oropharyngeal diagnosis. chemotherapy patients, 75% of patients receiving a mucositis occurs in 30-75% of hematopoietic cell transplant, and basically all the patients onset and rigor of mucositis which can cause arduousness © 2021 IJDSIR, All Rights Reserved Page >5000 cGy. It is very arduous to prognosticate the exact 470 experiencing head and neck radiation therapy in doses of Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) in treatment. OCT can detect early vicissitudes in mucositis which will ameliorate the aversion and treatment effect. Kawakami–Wrong et al. 2007 had done study in which five patients receiving neoadjuvant chemotherapy for primary breast cancer, oral mucositis, and OCT was used to clinically assessed and imaged. Imaging was scored Figure 19 utilizing a novel imaging-predicated scoring system. Oral In vivo optical coherence tomography (OCT) images mucositis assessment scale was used as the gold standard throughout the development of oral mucositis: OCT for conventional clinical assessment. Patients were images of ventral surface of tongue before (a), after 2 days evaluated on 0, 2, 4, 7, and 11 days after beginning the (b), after 7 days (c) and after 11 days (d) of chemotherapy. One blinded investigator viewed the OCT chemotherapy. In (a), smooth stratified squamous images. The findings in the study were: Transmutation in epithelium (1) is visible, separated from the submucosa epithelial thickness and subepithelial tissue integrity (2) by the basement membrane (3). Cumulative diagnostic (beginning on 2nd day), loss of continuity of surface imaging score is 0. In (b), epithelium is thinner by 50%, keratinized layer (beginning on 4th day), and loss of surface is still intact, although directly below the surface epithelial integrity (beginning on 4th day). Higher scores some breakdown is apparent (5). Subepithelial tissues just were obtained for imaging data compared to clinical below the basement membrane show some disruption. At scores earlier in treatment, suggesting the higher this point, the patient was totally asymptomatic. sensitivity of imaging-predicated diagnostic scoring to Cumulative diagnostic imaging score is 2. Further early mucositis change than the clinical scoring system. epithelial atrophy is seen after 7 and 11 days (c, d), with Imaging and clinical scores converged, after establishing infiltrate around the basement membrane and disruption of the mucositis. OCT identified oral changes induced by the adjacent epithelial and subepithelial tissues (4), and chemotherapy prior to their clinical manifestation, and the breakdown of the epithelial surface (5). Cumulative proposed scoring system for oral mucositis was validated diagnostic imaging score for (c) is 3 and for (d) is 5. From for the semi quantification of mucositis change Kawakami-Wong et al (2007) Muanza et al. in 2005 performed a study in murine Oral vascular malformation 36,37 radiation-induced mucositis models. The study concluded Ozawa et al. 2009 detected the two cases of vascular that OCT can be subsidiary for both qualitative and malformation, one with a capillary-venous malformation quantitative assessments of acute mucosal damages. There of the lower lip whereas the other with a reddish mass on were predominant transmutation in the mucosa detected the buccal mucosa. In these cases, OCT images correlated by well the OCT images afore visible manifestations, like ulcers became ostensible. macroscopic with histological structures, revealing well demarcated capillary vessel lumina and endothelial lining. cull of surgical treatment, particularly for vascular © 2021 IJDSIR, All Rights Reserved Page vascular lesions can be secondary for the diagnosis and 471 Cognizance of the size, area, and the border of the Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) anomalies, and hemangiomas in the oromaxillofacial histological animal studies have shown that gingival region. connective tissue forms a scar-like fibrous connective Mucocutaneous lesions tissue adjacent to titanium implant surfaces, while peri- Certain skin disorder can be detected by OCT, like lichen implantitis is characterised by a disorganised connective planus, pemphigus, pemphigoid etc. However, it requires tissue containing more vascular elements. The preliminary a specific intentness for skin disorders whose incidence is data demonstrate that in OCT images of healthy implant furthermore higher in the oral cavity . sites, collagen appears well organised and its birefringent Forsea et al. had done studies of 3 patients with psoriasis nature produces a characteristic high OCT signal intensity. and came to surmise that OCT showed typical thickening OCT images of soft tissue surrounding failing implants are of the epidermis, with epidermal protrusion into the characterised by linear signal deficits, low-intensity dermis, vigorous hyperkeratosis as a more tenebrous collagen signals, and pronounced increases in vascular superficial band. elements. OCT will improve clinical evaluation of peri- Forsea et al. had detected sarcoidosis with OCT, showed implant hypo-dense confluent rounded structures in the dermis advantages over existing diagnostic procedures. corresponding OCT can produce two- or three-dimensional images histopathology exam to granulomatous infiltrates. Temporo-Mandibular Joint Disc: and will provide significant depicting the topography of the implant sulcus and the 38 relationship of implants soft tissue interfaces. A fiberoptic The micro structure of temporomandibular disc by using clinical OCT system was used to obtain large size, 12 mm OCT was investigated by Marcauteanu and Colab. Two occlusal-apical OCT images. different OCT systems were used: an Enface (TDOCT) The advantage of OCT compared to non-optical imaging system working at 1300nm (C-scan and B scan mode) and modalities are its:40 a spectral OCT system (a FDOCT) system, working at  High depth and transversal solution 840nm (B scan mode). The OCT investigation of the  Contact-free and non-invasive operation, and the possibility to create temporomandibular joint discs revealed a homogeneous microstructure. The longer wavelength of the FDOCT  Function dependent image contrast offers a higher penetration depth (2.5mm in air), which is  OCT uses light for imaging of tissues hence patient is not exposed to ionizing radition important for the analysis of temporomandibular joint. Implantology: 39 OCT images provide quantitative information regarding  OCT helps in early diagnosis of oral diseases  OCT helps in real time monitoring of both hard and micro-structural architecture, including the character of the gingiva as well as that of the implant and the soft soft tissues.  It has excellent resolution and penetration depth and tissue relationships. More importantly, OCT identifies the hence can image the normal and abnormal changes in earliest signs of inflammation that are so minimal that the oral mucosa. clinical examination is unlikely to detect. OCT imaging offers the exciting potential to detect peri-implantitis before significant osseous destruction occurs. Several © 2021 IJDSIR, All Rights Reserved  T scan can be for occlusal mapping and help in recording the pattern of occlusion. 472 the tissues Page on soft Sowmya Hemanthakumar, et al. International Journal of Dental Science and Innovative Research (IJDSIR) The disadvantage of OCT are:41 novel  diagnosis. J. Periodontol. 2009, 81, 186–198. OCT has limited penetration depth in scattering media. approaches for periodontal 10. 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