Dentistry

Optical Coherence Tomography in Dentistry Scientific Developments to Clinical Applications (Textbook)

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Optical Coherence Tomography (OCT), a method to "see inside of things" without destroying them, has been applied to subjects ranging from materials science to medicine. This book focuses on the biomedical application of OCT in dentistry, covering topics from dental materials to clinical practice.   Since the introduction of the OCT method in ophthalmology and then dentistry in 1991, developments in OCT methods, particularly in biomedical areas, have led to its dissemination worldwide. The chapters of this book cover the basics and recent global advances of OCT in dentistry, including an overview of the method and its use in cariology, restorative dentistry, dental materials, endodontics, pediatric dentistry, orthodontics, prosthodontics, soft oral tissues, and nanodentistry.   This book will be of interest to both newcomers in the field as well as those already working in OTC, either in research and/or the clinic. It will be of great use in courses on optical imaging...

Imaging Modalities Pair to Help Practitioners Discern Tooth Decay

Imaging Modalities Pair to Help Practitioners Discern Tooth Decay To improve dental health, researchers at the University of California, San Francisco evaluated optical imaging techniques for their efficacy in the identification of secondary tooth decay, which can occur even if a tooth has already been filled. The researchers compared two techniques — shortwave infrared (SWIR) radiation reflectance and thermal imaging — with measurements obtained with optical coherence tomography (OCT) and micro-computed tomography (MicroCT). The results demonstrated the potential of SWIR reflectivity and OCT imaging methods for the clinical monitoring of secondary dental caries (i.e., dental cavity) lesions. The researchers considered cavities and methods of treatment as the impetus for the research. Treatment for cavities, known commonly as fillings, often fails over time. The restorative materials used to fill dental lesions do not always bond well to the surrounding healthy tooth structure. Microscopic leaks can form, which enable fluids and bacteria to pe...

Exploiting optical coherence tomography to evaluate wear in spiral dental polishing systems

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Exploiting optical coherence tomography to evaluate wear in spiral dental polishing systems This study aimed to evaluate the behavior of spiral polishing systems in restorative materials through optical coherence tomography (OCT). Performance of spiral polishers specific to resin and ceramics were evaluated. The surface roughness of restorative materials was measured, and images of the polishers were acquired by OCT and stereomicroscope. Surface roughness was reduced in ceramic and glass-ceramic composite polished with a system specific to resin (𝑝<0.01�<0.01). Surface area variation was observed on all polishers, except for the medium-grit polisher tested in ceramic (𝑝<0.05�<0.05). Similarity between images obtained through OCT and stereomicroscopy presented a Kappa inter- and intra-observer of 0.94 and 0.96, respectively. Then, OCT was able to evaluate wear areas in spiral polishers.

Assessment of the activity of secondary caries lesions with short-wavelength infrared, thermal, and optical coherence tomographic imaging

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Significance: Leakage in the interfaces between restorative materials and tooth structure allows for fluid and bacterial acid infiltration, causing restoration failure due to secondary caries. Dentists spend more time replacing composite restorations than placing new ones. Previous in vitro and in vivo studies on enamel and root surfaces using shortwave-infrared (SWIR) and thermal imaging during dehydration with forced air have been promising for assessing lesion activity. Aim: We hypothesized that SWIR reflectance and thermal imaging methods can be used to monitor the activity of secondary caries lesions around composite restorations. The objective of this study was to employ these methods to measure the rate of fluid loss from lesions during dehydration with forced air to assess lesion activity. Approach: Sixty-three extracted human teeth with total of 109 suspected secondary lesions were examined using SWIR and thermal imaging during dehydration. The thickness of the highly...

Exploiting optical coherence tomography to evaluate wear in spiral dental polishing systems

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This study aimed to evaluate the behavior of spiral polishing systems in restorative materials through optical coherence tomography (OCT). Performance of spiral polishers specific to resin and ceramics were evaluated. The surface roughness of restorative materials was measured, and images of the polishers were acquired by OCT and stereomicroscope. Surface roughness was reduced in ceramic and glass-ceramic composite polished with a system specific to resin (𝑝<0.01p<0.01). Surface area variation was observed on all polishers, except for the medium-grit polisher tested in ceramic (𝑝<0.05p<0.05). Similarity between images obtained through OCT and stereomicroscopy presented a Kappa inter- and intra-observer of 0.94 and 0.96, respectively. Then, OCT was able to evaluate wear areas in spiral polishers.

Assessment of demineralized tooth lesions using optical coherence tomography and other state-of-the-art technologies: a review

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Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in...

Optimal Surface Pre-Reacted Glass Filler Ratio in a Dental Varnish Effective for Inhibition of Biofilm-Induced Root Dentin Demineralization

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Abstract A unique type of dental varnish (DV) containing surface pre-reacted glass (S-PRG) fillers of different concentrations was evaluated to determine the unpresented optimal ratio for inhibiting root dentin bio-demineralization. S-PRG DVs (10% to 40%)— 10%-S , 20%-S , 30%-S , and 40%-S —were applied to bovine root dentin blocks and compared with controls— 0%-f (no S-PRG) and 5%-NaF (5%-NaF). The Streptococcus mutans biofilm challenge was executed inside and outside an oral biofilm reactor for 7 days. The specimens were examined using a confocal laser scanning microscope and swept-source optical coherence tomography. Furthermore, they were observed using a scanning electron microscope and analyzed using energy-dispersive X-ray spectroscopy. The roughness (SzJIS) due to leaching of DV materials and demineralization depth were significantly less in the S-PRG groups than the control groups ( p < 0.05). Complete or partially plugged dentinal tubules (DTs) were ob...

Automatic and quantitative measurement of alveolar bone level in OCT images using deep learning

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We propose a method to automatically segment the periodontal structures of the tooth enamel and the alveolar bone using convolutional neural network (CNN) and to measure quantitatively and automatically the alveolar bone level (ABL) by detecting the cemento-enamel junction and the alveolar bone crest in optical coherence tomography (OCT) images. The tooth enamel and the alveolar bone regions were automatically segmented using U-Net, Dense-UNet, and U 2 -Net, and the ABL was quantitatively measured as the distance between the cemento-enamel junction and the alveolar bone crest using image processing. The mean distance difference (MDD) measured by our suggested method ranged from 0.19 to 0.22 mm for the alveolar bone crest (ABC) and from 0.18 to 0.32 mm for the cemento-enamel junction (CEJ). All CNN models showed the mean absolute error (MAE) of less than 0.25 mm in the x and y coordinates and greater than 90% successful detection rate (SDR) at 0.5 mm for both the ABC and the CEJ. The...

Optical Attenuation Coefficients of Moist and Dry Tooth Determinate by Optical Coherence Tomography

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We investigated cross-sectional optical coherence tomography (OCT) images to determine the attenuation coefficients of moist and dry sound bovine teeth under near-infrared laser illumination. We acquired OCT images of the samples using a commercial swept-source OCT equipment, with a central wavelength of 1300 nm. In order to determine the attenuation coefficient of the samples, we studied the attenuation of light as it traveled through the dental tissue. The method considers only backscattered light, which restricts the contributions of speckles and reflective dispersion. To minimize errors related to the OCT equipment and because the operation influences the measurements, we revised various practical details associated with the OCT technique. Our results revealed significant differences between the attenuation coefficients of the dry and moist samples. We interpreted the values measured for dry/moist dentin (24.3/13.2 cm −1 ) and dry/moist enamel (3.1 /2.1 cm −1 ) based...

Bioinspired Anti-demineralization Enamel Coating for Orthodontics

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White spot lesions and enamel cracks are the 2 most prominent diseases that occur after orthodontic treatment and are caused by enamel demineralization from accumulated bacterial biofilms and/or enamel damage caused by the removal of residual adhesive after bracket debonding. Inspired by the self-assembled amelogenin nanoribbons in enamel, we developed an enamel coating with a self-assembling antimicrobial peptide, D-GL13K, to simultaneously reduce demineralization and residual adhesive. The self-assembled amphiphilic nanoribbons significantly increased the hydrophobicity of the etched enamel, which reduced the permeability of the coated enamel surfaces as desired. The antimicrobial activity of this coating was evaluated against Streptococcus mutans by colony-forming unit counting and live/dead assays. The anti-demineralization effect was demonstrated by the reduced demineralization depth analyzed by optical coherence tomography and the increased Vickers hardness. The coatings did n...

Optical coherence tomography systems for evaluation of marginal and internal fit of ceramic reconstructions

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Purpose: To evaluate the marginal and internal fit of lithium disilicate and zirconia crowns using two optical coherence tomography (OCT) systems in order to estimate inter-system variations. Materials and methods: Ten lithium disilicate and 10 cubic stabilized zirconia crowns were placed on prepared artificial teeth without cement. Marginal discrepancy and internal cement gap of the crowns were assessed on images obtained using a swept source OCT (SS-OCT) and a spectral domain OCT (SD-OCT). Medians and interquartile ranges were calculated for both materials and OCT systems. Thereafter, Wilcoxon signed rank test was carried out. Results: No significant difference was found between the two OCT systems for absolute marginal discrepancy of either lithium disilicate (SS-OCT: 182 µm, SD-OCT: 214 µm; p = .922) or zirconia crowns (SS-OCT: 116 µm, SD-OCT: 121 µm; p = .232). Regarding internal cement gap, no significant difference was found between the two OCT systems...

Praevium Research Inc Receives NIH Grant for Next generation MEMS-VCSEL technology for ultra-low-cost dental and periodontal swept source optical coherence tomography imaging

Praevium Research Inc Received a 2022 NIH Grant for $275,001 for Next generation MEMS-VCSEL technology for ultra-low-cost dental and periodontal swept source optical coherence tomography imaging. The principal investigator is Vijaysekhar Jayaraman. Below is a summary of the proposed study. This proposal aims to enable a new generation of high-speed, low-cost, wavelength-flexible swept source optical coherence tomography (SS-OCT) imaging device technology targeting applications in dental imaging and based on microelectromechanical systems vertical cavity surface emitting lasers (MEMS-VCSELs) and planar lightwave circuits (PLCs). MEMS-VCSELs provide an unmatched combination of high and variable axial scan rate, dynamic single mode operation enabling long imaging range, and the potential for low-cost volume manufacturing through wafer scale fabrication and testing. The proposed effort involves a collaboration between Praevium Research, which pioneered MEMS-VCSELs for SS-OCT, and the Un...

Evaluation of Incipient Enamel Caries at Smooth Tooth Surfaces Using SS-OCT

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(1) Background: Dental caries, if diagnosed at the initial stage, can be arrested and remineralized by a non-operative therapeutic approach preserving tooth structure. Accurate and reproducible diagnostic procedure is required for the successful management of incipient caries. The aim of this study was to evaluate the diagnostic accuracy of 3D swept-source optical coherence tomography (3D SS-OCT) for enamel caries at smooth tooth surface if the lesion was with remineralization. (2) Methods: Forty-seven tooth surfaces of 24 extracted human teeth visibly with/without enamel caries (ICDAS code 0-3) were selected and used in this study. The tooth surfaces of investigation site were cleaned and visually examined by four dentists. After the visual inspection, SS-OCT scanning was performed onto the enamel surfaces to construct a 3D image. The 2D tomographic images of the investigation site were chosen from the 3D dataset and dynamically displayed in video and evaluated by the examiners. A ...

Quantitative Assessment Methods of Early Enamel Caries with Optical Coherence Tomography: A Review

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Early detection of caries is an urgent problem in the dental clinic. Current caries detection methods do not detect early enamel caries accurately, and do not show microstructural changes in the teeth. Optical coherence tomography (OCT) can provide imaging of tiny, demineralized regions of teeth in real time and noninvasively detect dynamic changes in lesions with high resolution and high sensitivity. Over the last 20 years, researchers have investigated different methods for quantitative assessment of early caries using OCT. This review provides an overview of the principles of enamel caries detection with OCT, the methods of characterizing caries lesion severity, and correlations between OCT results and measurements from multiple histological detection techniques. Studies have shown the feasibility of OCT in quantitative assessment of early enamel lesions but they vary widely in approaches. Only integrated reflectivity and refractive index measured by OCT have proven to have stron...

Local axis orientation mapped by polarization sensitive optical coherence tomography provides a unique contrast to identify caries lesions in enamel

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Due to rod-like hydroxyapatite crystal organizations, dental enamel is optically anisotropic, i.e., birefringent. Healthy enamel is known to be intrinsically negatively birefringent. However, when demineralization of enamel occurs, a considerable number of inter-crystallite spaces would be created between the crystallites in the enamel, which could lead to a sign reversion in birefringence of the enamel structure. We propose that this sign reversion can be leveraged in polarization sensitive OCT (PSOCT) imaging to differentiate early caries lesions from healthy enamel. In this study using PSOCT, we first confirm that the change in birefringence sign (negative to positive) can lead to a 90-degree alteration in the local axis orientation because of the switch between the fast and slow optic axes. We then demonstrate, for the first time, that the local axis orientation can be utilized to map and visualize the WSLs from the healthy enamel with a unique contrast. Moreover, the sharp alte...

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