• Imaging Science in Dentistry
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• v.42 no.1
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• pp.25-33
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• 2012

Purpose : This study was performed to determine the accuracy of linear measurements on three-dimensional (3D) images using multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). Materials and Methods : MDCT and CBCT were performed using 24 dry skulls. Twenty-one measurements were taken on the dry skulls using digital caliper. Both types of CT data were imported into OnDemand software and identification of landmarks on the 3D surface rendering images and calculation of linear measurements were performed. Reproducibility of the measurements was assessed using repeated measures ANOVA and ICC, and the measurements were statistically compared using a Student t-test. Results : All assessments under the direct measurement and image-based measurements on the 3D CT surface rendering images using MDCT and CBCT showed no statistically difference under the ICC examination. The measurements showed no differences between the direct measurements of dry skull and the image-based measurements on the 3D CT surface rendering images (P>.05). Conclusion : Three-dimensional reconstructed surface rendering images using MDCT and CBCT would be appropriate for 3D measurements.

• Imaging Science in Dentistry
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• v.47 no.4
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• pp.227-231
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• 2017

Purpose: Sialolithiasis is one of the most prevalent large obstructive disorders of the submandibular glands. The aim of this study was to investigate submandibular sialolithiasis with computed tomography (CT) and scintigraphy, with a particular focus on the relationship between CT values of the submandibular glands and their excretion rate. Materials and Methods: Fifteen patients with submandibular sialolithiasis who underwent CT and salivary gland scintigraphy were included in this study. The relationship between the CT values of submandibular glands with and without sialoliths and salivary gland excretion measured using salivary gland scintigraphy was statistically analyzed. Dynamic images were recorded on the computer at 1 frame per 20 seconds. The salivary gland excretion fraction was defined as A (before stimulation test [counts/frame]) / B (after stimulation test [counts/frame]) using time-activity curves. Results: The CT values in the submandibular glands with and without sialoliths was $9.9{\pm}44.9$ Hounsfield units(HU) and $34.2{\pm}21.8HU$, respectively (P=.233). Regarding the salivary gland excretion fraction using scintigraphy, the A/B value in the submandibular glands with sialoliths ($1.09{\pm}0.23$) was significantly lower than in the submandibular glands without sialoliths($1.99{\pm}0.57$, P=.000). Conclusion: Assessments of the CT values and the salivary gland excretion fraction using scintigraphy in the submandibular glands seem to be useful tools evaluating submandibular sialolithiasis.

• Imaging Science in Dentistry
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• v.32 no.4
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• pp.201-206
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• 2002

Purpose : To evaluate the radiographic change of operation sites after orthognathic surgery using the digital image processing and fractal analysis. Materials and Methods : A series of panoramic radiographs of thirty-five randomly selected patients who had undergone mandibular orthognathic surgery (bilateral sagittal split ramus osteotomy) without clinical complication for osseous healing, were taken. The panoramic radiographs of each selected patient were taken at pre-operation (stage 0), 1 or 2 days after operation (stage 1), 1 month after operation (stage 2), 6 months after operation (stage 3), and 12 months after operation (stage 4). The radiographs were digitized at 600 dpi, 8 bit, and 256 gray levels. The region of interest, centered on the bony gap area of the operation site, was selected and the fractal dimension was calculated by using the tile-counting method. The mean values and standard deviations of fractal dimension for each stage were calculated and the differences among stage 0, 1, 2, 3, and 4 were evaluated through repeated measures of the ANOVA and paired t-test. Results : The mean values and standard deviations of the fractal dimensions obtained from stage 0, 1, 2, 3, and 4 were 1.658±0.048, 1.580±0.050, 1.607±0.046, 1.624±0.049, and 1.641 ±0.061, respectively. The fractal dimensions from stage 1 to stage 4 were shown to have a tendency to increase (p < 0.05). Conclusion: The tendency of the fractal dimesion to increase relative to healing time may be a useful means of evaluating post-operative bony healing of the osteotomy site.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.1
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• pp.128-136
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• 1992

This study was undertakened to investigate the change of image characteristics on dental films according to the process of using time of processing solution in automatic processor. Base + fog density, film density and subject contrast were measured with the digital densitometer, the pH of developing and fixing solution were measured with Digital pH / ION Meter. The following results were obtained: 1. Base + fog density was increased with the process of using time of the processing solution and was over the maximum permissible base + fog density 0.25 from the 3rd day. 2. Film density was increased with the process of using time of the processing solution. 3. Subject contrast was decreased with the process of using time of the processing solution. 4. The pH of the developing solution was decreased with the process of using time, the pH of the fixing solution was increased.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.281-285
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• 2000

An uncommon case of a patient with recurrent mandibular ameloblastoma involving various adjacent soft tissues is presented with plain film radiography, computed tomography and magnetic resonance imaging (MRI) and bone scan. The tumor involved mandible and eroded several bones including foramen ovale. This case shows that although an ameloblastoma primarily affect mandible, exact radiographic evaluation of tumor extent will assist the surgeon in the progress of rational approaches to the management of ameloblastoma.

• Imaging Science in Dentistry
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• v.42 no.2
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• pp.111-114
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• 2012

Non-Hodgkin's lymphomas are a group of highly diverse malignancies and have a strong tendency to affect organs and tissues that do not ordinarily contain lymphoid cells. Primary extra nodal lymphoma of the hard palate is rare. Here, we present a case of diffuse large B cell lymphoma in a 60-year-old male patient that manifested as slightly painful ulcerated growth on the edentulous right maxillary alveolar ridge extending onto the palate, closely resembling carcinoma of the alveolar ridge. Computed tomography images showed the involvement of the maxillary sinus and right nasal cavity, along with destruction of hard palate, superiorly extending into the orbit. This case report highlights the importance of imaging to evaluate the exact extent of such large malignant lesions, which is essential for treatment planning.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.2
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• pp.199-206
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• 1993

본 연구는 1987년 1월부터 1991년 12월까지 연세대학교치과병원 구강악안면외과에 과두 골절이 의심되어 내원한 환자중 임상 및 방사선학적 소견에서 하악과두 골절로 진단되어 비외과적 치료를 받은 12세 미만의 13명의 소아환자를 연구 대상으로 하여 임상 및 방사선학적 소견을 분석하여 다음과 같은 결론을 얻었다. 비외과적인 보존적 또는 기능적 치료를 받은 후의 결과는 양호하였으며, 골의 재생과 개조는 신속하여 골 구조는 기능 중에 가해진 힘에 반응한다는 Wolff의 법칙과 일치하는 듯이 보였다. 두 예의 골절탈구에서 과두의 단축 및 과두가 골절된 악관절에서 clicking음을 보였으나 저작하거나 개구시에 큰 어려움은 없었다. 술후 관찰기간이 불충분하였으나 본 예의 대부분에서 비외과적인 술식에도 만족스러운 치료결과를 보였다.

• Imaging Science in Dentistry
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• v.39 no.4
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• pp.209-212
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• 2009

Bifid mandibular canal can be an anatomic variation. This condition can lead to complication when performing mandibular anesthesia or during extraction of lower third molar, placement of implants and surgery in the mandible. Four patients underwent preoperative imaging for extraction of third molars using CBCT (CB Mercuray, Hitachi, Japan). The axial images were processed with CBworks program 2.1 (CyberMed Inc., Seoul, Korea). The branches for supplying the lower third molar were identified mainly on cross-sectional and panoramic images of CBCT. Since the location and configuration of mandibular canal variations are important in any mandibular surgical procedures, we report 4 cases of bifid mandibular canal with panoramic and the CBCT images.

• Imaging Science in Dentistry
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• v.36 no.3
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• pp.123-129
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• 2006

The use of computed tomography for dental procedures has increased recently. Cone beam computed tomography (CBCT) systems have been designed for imaging hard tissues of the dentomaxillofacial region. CBCT is capable of providing high resolution in images of high diagnostic quality. This technology allows for 3-dimensional representation of the dentomaxillofacial skeleton with minimal distortion, but at lower equipment cost, simpler image acquisition and lower patient dose. Because this technology produces images with isotropic sub-millimeter spatial resolution, it is ideally suited for dedicated dentomaxillofacial imaging. In this paper, we provide a brief overview of cone beam scanning technology and compare it with the fan beam scanning used in conventional CT and the basic principles of currently available CBCT systems.

• Journal of Periodontal and Implant Science
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• v.46 no.2
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• pp.116-127
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• 2016

Purpose: The objective of this study was to investigate the relationships between primary implant stability as measured by impact response frequency and the structural parameters of trabecular bone using cone-beam computed tomography(CBCT), excluding the effect of cortical bone thickness. Methods: We measured the impact response of a dental implant placed into swine bone specimens composed of only trabecular bone without the cortical bone layer using an inductive sensor. The peak frequency of the impact response spectrum was determined as an implant stability criterion (SPF). The 3D microstructural parameters were calculated from CT images of the bone specimens obtained using both micro-CT and CBCT. Results: SPF had significant positive correlations with trabecular bone structural parameters (BV/TV, BV, BS, BSD, Tb.Th, Tb.N, FD, and BS/BV) (P<0.01) while SPF demonstrated significant negative correlations with other microstructural parameters (Tb.Sp, Tb.Pf, and SMI) using micro-CT and CBCT (P<0.01). Conclusions: There was an increase in implant stability prediction by combining BV/TV and SMI in the stepwise forward regression analysis. Bone with high volume density and low surface density shows high implant stability. Well-connected thick bone with small marrow spaces also shows high implant stability. The combination of bone density and architectural parameters measured using CBCT can predict the implant stability more accurately than the density alone in clinical diagnoses.