Dental Optical Coherence Tomography Research Articles

Development of handheld optical coherence tomography based on commercial intra‐oral scanner shape for extended clinical utility in dentistry

AbstractThe main objective of this study is to develop a handheld dental optical coherence tomography (OCT) system capable of imaging the target area of the teeth in the oral cavity and demonstrate the applicability of the developed system to in vivo dental disease diagnosis based on a user‐friendly scanner form. The design of the developed system is based on mimicking the shape of a commonly used commercial intra‐oral scanner (IOS) so that the system users do not feel awkward when using it. A microelectromechanical system (MEMS) scanning unit was used to optimize the overall size of the system, and the optical axis was designed in a Z‐shape to maximize the beam size reflected by the MEMS mirror. A pre‐study of in vivo oral scanning was performed to demonstrate the enhanced clinical feasibility of the developed system. Furthermore, the main experiment classified teeth with worn cervical regions into two groups according to the cervical abrasion shape. The developed dental OCT system produced a three‐dimensional image of the scanning area and quantitatively analyzed the margin gap through an A‐scan profile based on cross‐sectional images. This study confirms the effectiveness of the developed handheld dental OCT system in actual dental clinical practice, and we expect our system to be utilized for various dental diseases, not only for diagnosing a cervical abrasions.

Optical Coherence Tomography for Patients with Developmental Disabilities: A Preliminary Study.

Dental radiographs are essential for diagnosis and treatment planning, but are sometimes difficult to acquire for patients with developmental disabilities (PDD). Optical Coherence Tomography (OCT) is a non-ionizing imaging modality that has the potential application as an alternative to dental radiographs for PDD. This study aimed to determine the feasibility of intraoral OCT imaging for PDD. Ten participants were recruited in the Dental Education in the Care of Persons with Disabilities (DECOD) Clinic to explore the utility of dental OCT. The prototype system (Yoshida Dental) creates in-depth and three-dimensional images of teeth. The participants indicated their degree of pain during imaging on the Wong-Baker FACES Pain Rating Scale, and the degree of discomfort after imaging on a visual analog scale. OCT can be used for patients with developmental disabilities with minimal levels of pain and discomfort, without ionizing radiation.

Disease activation maps for subgingival dental calculus identification based on intelligent dental optical coherence tomography

AbstractDuring the treatment of periodontitis, removal of dental calculus is essential but still tricky despite developments of several imaging modalities. In this research, we propose a novel approach to provide an intuitive guidance, to automatically detect the present of subgingival calculus, and to identify the site of the lesion in optical coherence tomography images based on convolutional neural network model and the class activation maps technique. Our result shows good visualizations of dental calculus both in B‐scan and in volumetric view. We believe the improvement can break down the technical barrier and finally facilitate the prevalence of dental optical coherence tomography.

New bulk-fill composite system with high irradiance light polymerization: Integrity and degree of conversion

ObjectiveThe study used optical coherence tomography (OCT) and micro Raman microscopy (mRM) to investigate internal defect (ID) and degree of conversion (DC) of two bulk-fill composite systems with high-irradiance or conventional light polymerization settings. MethodsThe ID and DC of the new bulk-fill composites; Tetric PowerFill (PwrPst) and Tetric PowerFlow (PwrFlw) were compared with the predecessor bulk-fill composites; Tetric EvoCeram Bulkfill (EvoPst) and Tetric EvoFlow Bulkfill (EvoFlw), using LED light curing unit in two settings; normal (LED-Nrm: 1000 mW/cm2, 10-s) or PowerCure (LED-Pwr: 3000 mW/cm2, 3-s). ID formation was observed in bonded cylindrical composite cavities (4-mm depth, 3-mm diameter) using Yoshida Dental OCT. From the vertically projected 2D image, ID area percentage (ID-A%) was calculated. DC at the top and bottom and bottom/top DC ratio (DC-R%) of 4-mm thick discs was calculated using mRM. All data were statistically analyzed at significance level of α = 0.05. ResultsFlowable composites in LED-Pwr showed smaller ID frequencies than other groups (PwrFlw: 0/8, EvoFlw: 2/8) (p < 0.05). Composite type significantly affected ID-A%, DC and DC-R% (p < 0.001), while light settings significantly affected ID-A% but not DC and DC-R% (p > 0.05). In both light settings, EvoPst showed the lowest DC-R% (<80%). SignificanceInternal defect and degree of conversion of bulk-fill composites were affected by their composition and light settings. There was a tendency for less defects and better polymerization for the flowable bulk-fills. The new flowable bulk-fill composite with 3-seconds high irradiance light curing showed no defect formation.

Comparisons of the diagnostic accuracies of optical coherence tomography, micro-computed tomography, and histology in periodontal disease: anex vivostudy

PurposeOptical coherence tomography (OCT) is a noninvasive diagnostic technique that may be useful for both qualitative and quantitative analyses of the periodontium. Micro-computed tomography (micro-CT) is another noninvasive imaging technique capable of providing submicron spatial resolution. The purpose of this study was to present periodontal images obtained using ex vivo dental OCT and to compare OCT images with micro-CT images and histologic sections.MethodsImages of ex vivo canine periodontal structures were obtained using OCT. Biologic depth measurements made using OCT were compared to measurements made on histologic sections prepared from the same sites. Visual comparisons were made among OCT, micro-CT, and histologic sections to evaluate whether anatomical details were accurately revealed by OCT.ResultsThe periodontal tissue contour, gingival sulcus, and the presence of supragingival and subgingival calculus could be visualized using OCT. OCT was able to depict the surface topography of the dentogingival complex with higher resolution than micro-CT, but the imaging depth was typically limited to 1.2–1.5 mm. Biologic depth measurements made using OCT were a mean of 0.51 mm shallower than the histologic measurements.ConclusionsDental OCT as used in this study was able to generate high-resolution, cross-sectional images of the superficial portions of periodontal structures. Improvements in imaging depth and the development of an intraoral sensor are likely to make OCT a useful technique for periodontal applications.

Sensing of Tooth Microleakage Based on Dental Optical Coherence Tomography

This study describes microleakage sensing based on swept-source optical coherence tomography (SS-OCT). With a handheld scanning probe, the SS-OCT system can provide portable real-time imaging for clinical diagnosis. Radiography is the traditional clinical imaging instrument used for dentistry; however, it does not provide good contrast images between filling material and the enamel of treated teeth with microleakage. The results of this study show that microleakage can be detected with oral probing using SS-OCTin vivo. The calculated microleakage length was 401 μm and the width is 148 μm, which is consistent with the related histological biopsy measurements. The diagnosis of microleakage in teeth could be useful for prevention of secondary caries in the clinical treatment plans developed in the field of oral medicine.

Dental Optical Coherence Tomography

This review paper describes the applications of dental optical coherence tomography (OCT) in oral tissue images, caries, periodontal disease and oral cancer. The background of OCT, including basic theory, system setup, light sources, spatial resolution and system limitations, is provided. The comparisons between OCT and other clinical oral diagnostic methods are also discussed.

Design of highly nonlinear dispersion flattened hexagonal photonic crystal fibers for dental optical coherence tomography applications

In this paper, we propose a highly nonlinear dispersion flattened hexagonal photonic crystal fiber (HNDF-HPCF) with nonlinear coefficients as large as 57.5W−1 km−1 at 1.31 μm wavelength for dental optical coherence tomography (OCT) applications. This HNDF-HPCF offers not only large nonlinear coefficient but also very flat dispersion slope and very low confinement losses. Using these characteristics of our proposed PCF, it is shown through simulations by using finite difference method with an anisotropic perfectly matched boundary layer that this PCF offers the efficient supercontinuum (SC) generation for dental OCT applications at 1.31 μm wavelength using a picosecond pulse easily produced by commercially available less expensive laser sources. Coherent length of light source using SC is found 10 μm and the spatial resolutions in the depth direction for dental applications of OCT are found about 6.1 μm for enamel and 6.5 μm for dentin.

歯科用OCT画像診断機器の開発と歯科臨床応用

歯科用OCT画像診断機器の開発と歯科臨床応用

Design of all normal dispersion highly nonlinear photonic crystal fibers for supercontinuum light sources: Applications to optical coherence tomography systems

In this paper, we investigate the generation of supercontinuum (SC) light source based on a highly nonlinear Germanium (Ge) doped photonic crystal fiber (HNL-GePCF) with all normal group velocity dispersion (GVD). By doping 3% higher refractive index Ge inside silica, nonlinear coefficient γ is increased as large as 110.6 W −1 km −1 at 1.31 μ m . Using finite element method (FEM) with a circular perfectly matched boundary layer (PML), it is shown through simulations that the proposed HNL-GePCF offers an efficient SC generation for dental optical coherence tomography (OCT) applications at 1.31 μ m . By propagating sech 2 picosecond optical pulses having 2.5 ps and 1.0 ps pulsewidth at a full width at half maximum (FWHM) through the proposed HNL-GePCF, output optical pulses are analyzed by the split-step Fourier method to obtain the spectral contents. Simulation results show that 105 m of the proposed HNL-GePCF can produce 100 nm spectrum (10 dB bandwidth) at 1.31 μ m for 2.5 ps input optical pulse and 110 m of such HNL-GePCF can produce 140 nm spectrum (10 dB bandwidth) for 1.0 ps input optical pulse. Therefore, the highest longitudinal resolutions in the depth direction for dental OCT are found about 3.28 μ m for enamel and 3.51 μ m for dentin.

Design of highly nonlinear octagonal photonic crystal fiber with near-zero flattened dispersion at 1.31μm waveband

This paper presents a highly nonlinear octagonal photonic crystal fiber (HN-OPCF) with a Ge-doped core for dental optical coherence tomography (OCT) applications. The simulation results show that a nonlinear coefficient of 56.3W−1 km−1 and the flattened dispersion of less than −1:0 ps/(nm·km) are obtained in 75 nm waveband (1265–1340 nm). Owing to its high nonlinear coefficient and flattened dispersion, the HN-OPCF is expected to be suitable for supercontinuum generation, which is very important in OCT applications. The numerical simulation results demonstrate that the proposed HN-OPCF can generate wideband supercontinuum.

Improved fast scanning delay line in optical coherence tomography applications utilizing fiber stretcher

We demonstrate an improved fiber-stretcher-based scanning delay line in terms of both the scanning speed and the delay range. Such a module is essential to optical coherence tomography (OCT) applications. An 18-mm delay range at 2-kHz scanning frequency is achieved and verified in a dental OCT setup. Repeatability and reliability of the new design are further evaluated through multiple trials within days. The results confirm its feasibility into practical applications.

Dental optical coherence tomography: a comparison of two in vitro systems

Dental optical coherence tomography: a comparison of two in vitro systems

Dental OCT

We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.