• The Journal of the Korean dental association
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• v.54 no.9
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• pp.704-711
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• 2016

Radiologic images in dentistry are essential to perform the diagnosis, treatment, and tracking process of prognosis, thus the ability of accurate evaluation in the diagnostic images is requested for dental clinician. Radiologic interpretation means recognition of a normality and an abnormality and to report the possible diagnosis and differential diagnosis list. Therefore, dental clinicians should be familiar with the basic principle of interpretation of intraoral and extraoral radiographic images primarily used in dental clinics. Recently, dental cone beam CT is widely used for diagnositc process, thus understanding the three dimensional images is requested. The objective of this manuscript is to help the dental clinicians to interpret accurately the diagnostic images by introducing the basic principles of the step by step analytic process in the appearance of a lesion.

• Imaging Science in Dentistry
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• v.39 no.3
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• pp.115-120
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• 2009

Purpose : The purpose of this study was to determine a conversion coefficient for Hounsfield Units(HU) to material density ($g\;cm^{-3}$) obtained from cone-beam computed tomography ($CBMercuRay^{TM}$) data and to measure the hard tissue density based on the Hounsfield scale on dental head phantom. Materials and Methods : CT Scanner Phantom (AAPM) equipped with CT Number Insert consists of five cylindrical pins of materials with different densities and teflon ring was scanned by using the $CBMercuRay^{TM}$ (Hitachi, Tokyo, Japan) volume scanner. The raw data were converted into DICOM format and the HU of different areas of CT number insert measured by using $CBWorks^{TM}$. Linear regression analysis and Student t-test were performed statistically. Results : There was no significant difference (P > 0.54) between real densities and measured densities. A linear regression was performed using the density, $\rho$($g\;cm^{-3}$), as the dependent variable in terms of the HU (H). The regression equation obtained was $\rho=0.00072H-0.01588$ with an $R^2$ value of 0.9968. Density values based on the Hounsfield scale was $1697.1{\pm}24.9\;HU$ in cortical bone, $526.5{\pm}44.4\;HU$ in trabecular bone, $2639.1{\pm}48.7\;HU$ in enamel, $1246.1{\pm}39.4\;HU$ in dentin of dental head phantom. Conclusion : CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

• The Journal of the Korean dental association
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• v.54 no.9
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• pp.712-728
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• 2016

These days, the clinical course of dental imaging sector has done a lot of implant-related imaging courses, including cone beam CT. In contrast, the general image reading course is not given a lot of opportunities to learn. Therefore, it is imperative that we talk about the general image interpretation that can be read easily applied in a dental clinic. When we see a strange radiographic finding of our patient in the dental clinic, we should first check whether the radiographic finding is a normal finding or a morbidity. If the finding is diagnosed as a morbidity, you should make plans for the appropriate therapy. The most important step is classification between normal state and morbidity. Some lesions may occur without any clinical symptoms. Therefore, we should read all the parts of radiographs, even the patient does not have clinical symptoms.

• Imaging Science in Dentistry
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• v.54 no.2
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• pp.121-127
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• 2024

Purpose: Preoperative identification of the intraosseous posterior superior alveolar artery (PSAA) is critical when planning sinus surgery. This study was conducted to determine the distance between the cementoenamel junction and the PSAA, as well as to identify factors influencing the detection of the PSAA on cone-beam computed tomography (CBCT). Materials and Methods: In total, 254 CBCT scans of maxillary sinuses, acquired with 2 different scanners, were examined to identify the PSAA. The distance from the cementoenamel junction (CEJ) to the PSAA was recorded at each maxillary posterior tooth position. Binomial logistic regression and multiple linear regression were employed to evaluate the effects of scanner type, CBCT parameters, sex, and age on PSAA detection and CEJ-PSAA distance, respectively. P-values less than 0.05 were considered to indicate statistical significance. Results: The mean CEJ-PSAA distances at the second molar, first molar, second premolar, and first premolar positions were 17.0±4.0 mm, 21.8±4.1 mm, 19.5±4.7 mm, and 19.9±4.9 mm for scanner 1, respectively, and 17.3±3.5 mm, 16.9±4.3 mm, 18.5±4.1 mm, and 18.4±4.3 mm for scanner 2. No independent variable significantly influenced PSAA detection. However, tooth position (b=-0.67, P<0.05) and scanner type (b=-1.3, P<0.05) were significant predictors of CEJ-PSAA distance. Conclusion: CBCT-based estimates of CEJ-PSAA distance were comparable to those obtained in previous studies involving cadavers, CT, and CBCT. The type of CBCT scanner may slightly influence this measurement. No independent variable significantly impacted PSAA detection.

• Imaging Science in Dentistry
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• v.44 no.1
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• pp.21-29
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• 2014

Purpose: To determine the conversion coefficients (CCs) from the dose-area product (DAP) value to effective dose in cone-beam CT. Materials and Methods: A CBCT scanner with four fields of view (FOV) was used. Using two exposure settings of the adult standard and low dose exposure, DAP values were measured with a DAP meter in C mode ($200mm{\times}179mm$), P mode ($154mm{\times}154mm$), I mode ($102mm{\times}102mm$), and D mode ($51mm{\times}51mm$). The effective doses were also investigated at each mode using an adult male head and neck phantom and thermoluminescent chips. Linear regressive analysis of the DAP and effective dose values was used to calculate the CCs for each CBCT examination. Results: For the C mode, the P mode at the maxilla, and the P mode at the mandible, the CCs were 0.049 ${\mu}Sv/mGycm^2$, 0.067 ${\mu}Sv/mGycm^2$, and 0.064 ${\mu}Sv/mGycm^2$, respectively. For the I mode, the CCs at the maxilla and mandible were 0.076 ${\mu}Sv/mGycm^2$ and 0.095 ${\mu}Sv/mGycm^2$, respectively. For the D mode at the maxillary incisors, molars, and mandibular molars, the CCs were 0.038 ${\mu}Sv/mGycm^2$, 0.041 ${\mu}Sv/mGycm^2$, and 0.146 ${\mu}Sv/mGycm^2$, respectively. Conclusion: The CCs in one CBCT device with fixed 80 kV ranged from 0.038 ${\mu}Sv/mGycm^2$ to 0.146 ${\mu}Sv/mGycm^2$ according to the imaging modes and irradiated region and were highest for the D mode at the mandibular molar.

• Imaging Science in Dentistry
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• v.54 no.3
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• pp.283-288
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• 2024

Purpose: Given the growing use of cone-beam computed tomography (CBCT) scans, this study assessed radiation exposure from these scans in the context of national guidelines and recommended dose limits. Materials and Methods: The current literature was reviewed to quantify the benefit of opportunistic diagnosis of carotid artery calcification relative to the potential risk of radiation-induced cancer. Results: The average radiation from CBCT at its largest field of view and highest resolution possible amounts to a reasonable but still low ionizing radiation exposure. This exposure is comparable to 22 days of background radiation and is notably lower than the radiation exposure from medical CT scans. According to the risk assessment analysis, the risk of stroke events involving internal and external carotid artery calcification (CAC) was 202 and 67 per 100,000 individuals, respectively. In contrast, the estimated risk of radiation-induced cancer associated with CBCT was notably lower, at 0.6 per 100,000. Conclusion: The present study advocates for a comprehensive assessment of CBCT scans encompassing the areas of the internal and external carotid arteries by a knowledgeable professional, given the potential advantages of early detection of vascular abnormalities. Dental professionals who take scans involving these areas need to be mindful of reporting these findings and refer patients to their primary care physician for further investigation.

• Imaging Science in Dentistry
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• v.38 no.1
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• pp.17-22
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• 2008

Purpose: It is important to determine the bucco-lingual inclination of implants on radiographs before the implant surgery. The purpose of this study was to compare the buccolingual inclination in alveolar bone and the tooth with dental cone beam CT and to prepare the standard for the buccolingual inclination of implant. Materials and Methods: Axial, panoramic, and buccolingually sectioned images of 80 implant cases with stent including straight marker using CB $Mercuray^{TM}$ (Hitachi, Japan) were evaluated. The comparison of the buccolingual inclination of remained alveolar bone with the tooth and the marker on butcolingually sectioned views was performed statistically. Results: The average buccolingual inclination of remained alveolar bone and tooth was $82.8{\pm}4.6^{\circ}\;and\;85.8{\pm}4.7^{\circ}$ (p<0.05, r=0.96) at the 1st molar area and $76.4{\pm}1.7^{\circ}\;and\;82.7{\pm}1.7^{\circ}$ respectively (p>0.05, r=0.12) at the 2nd premolar area in upper jaw. The average buccolingua1 inclination of remained alveolar bone and tooth was $81.3{\pm}8.3^{\circ}\;and\;87.5{\pm}6.3^{\circ}$ (p>0.05, r=0.85) at the lower 2nd premolar area and $94.3{\pm}6.6^{\circ}\;and\;93.3{\pm}7.2^{\circ}$ respectively (p>0.05, r=0.91) at the 1st molar area in lower jaw. The inclinations of markers were very different from those of remained bone at the most of areas except the upper 2nd premolar area (r=0.79). Conclusion: We recommend dental CBCT analysis for determining the buccolingual inclination of dental implant, because of significant difference, in average, between the bucco1ingual inclination of remained alveolar bone and tooth.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.289-299
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• 2009

Objective: The purpose of the present study was to evaluate the effectiveness of the use of Head Posture Aligner (HPA) during cone-beam computed tomography (CBCT) scan in generation of frontal cephalograms using 3D CBCT images. Methods: CBCT scans and frontal cephalograms were made in 30 adult individuals. While a couple of CBCT scan was made for one subject, one was made with conventional method, without use of HPA, the other was acquired with the use of HPA. After creation of virtual frontal cephalogram from each 3D CBCT image, it was traced and compared with the tracing of real frontal cephalogram. Results: In the comparison of the measurements, the virtual cephalograms with the use of HPA did not show statistically significant differences with the real cephalograms whereas the virtual cephalograms without the use of HPA presented significant differences with real cephalograms in many measurements. In the correlation analysis with the measurements of the real cephalograms, the virtual cephalograms with the use of HPA showed higher correlations in all measurements than the virtual cephalograms without the use of HPA. Conclusions: Measurements from CBCT-generated cephalograms become similar to those from real cephalograms with the use of HPA during CBCT scan. Thus, the use of HPA is suggested during the CBCT scan in order to construct accurate virtual frontal cephalograms using 3D CBCT images.

• The Journal of the Korean dental association
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• v.58 no.11
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• pp.700-712
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• 2020

The conventional mouthguard fabrication process consists of elastomeric impression taking and followed gypsum model making is now into intraoral scanning and direct mouthguard 3D printing with an additive manufacturing process. Also, dental professionals can get various diagnostic data collection such as facial scans, cone-beam CT, jaw motion tracking, and intraoral scan data to superimpose them for making virtual patient datasets. To print mouthguards, dental CAD software allows dental professionals to design mouthguards with ease. This article shows how to make 3D printed mouthguard step by step.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.1
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• pp.60-69
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• 2016

Purpose: The objective of this study was to compare the accuracy of digital models from 3 dimentional (3D) optical scanner and cone beam computed tomography (CBCT). Materials and Methods: We obtained digital models from 11 pairs of stone casts using a 3D optical scanner and a CBCT, and compared the accuracy of the models. Results: The error range of average positive distance was 0.059 - 0.117 mm and negative distance was 0.066 - 0.146 mm. Statistically (P < 0.05), average positive distance was larger than $70{\mu}m$ and shorter than $100{\mu}m$, and that of negative distance was larger than $100{\mu}m$ and shorter than $120{\mu}m$. Conclusion: We concluded that the accuracy of digital models generated from CBCT is not appropriate to make final prostheses. However, it may be acceptable for provisional restorations and orthodontic diagnoses with respect to the accuracy of the digitalization.