Sang-Sun Han

Comparison of conventional lateral cephalograms with corresponding CBCT radiographs

Purpose This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for three-dimensional (3D) assessments. Materials and Methods The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. Results The linear measurements between the two imaging modalities were not statistically different (p>0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p>0.05) with the exception of the gonial angle, ANB difference, and facial convexity. Conclusion Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.

Regulation of root patterns in mammalian teeth

Mammalian teeth have diverse pattern of the crown and root. The patterning mechanism of the root position and number is relatively unknown compared to that of the crown. The root number does not always match to the cusp number, which has prevented the complete understanding of root patterning. In the present study, to elucidate the mechanism of root pattern formation, we examined (1) the pattern of cervical tongues, which are tongue-like epithelial processes extending from cervical loops, (2) factors influencing the cervical tongue pattern and (3) the relationship among patterns of cusp, cervical tongue and root in multi-rooted teeth. We found a simple mechanism of cervical tongue formation in which the lateral growth of dental mesenchyme in the cuspal region pushes the cervical loop outward, and the cervical tongue appears in the intercuspal region subsequently. In contrast, when lateral growth was physically inhibited, cervical tongue formation was suppressed. Furthermore, by building simple formulas to predict the maximum number of cervical tongues and roots based on the cusp pattern, we demonstrated a positive relationship among cusp, cervical tongue and root numbers. These results suggest that the cusp pattern and the lateral growth of cusps are important in the regulation of the root pattern.

Cone beam CT findings of retromolar canals: Report of cases and literature review

A retromolar canal is an anatomical variation in the mandible. As it includes the neurovascular bundle, local anesthetic insufficiency can occur, and an injury of the retromolar canal during dental surgery in the mandible may result in excessive bleeding, paresthesia, and traumatic neuroma. Using imaging analysis software, we evaluated the cone-beam computed tomography (CT) images of two Korean patients who presented with retromolar canals. Retromolar canals were detectable on the sagittal and cross-sectional images of cone-beam CT, but not on the panoramic radiographs of the patients. Therefore, the clinician should pay particular attention to the identification of retromolar canals by preoperative radiographic examination, and additional cone beam CT scanning would be recommended.

Validating of the pre-clinical mouse model for metastatic breast cancer to the mandible

Metastatic breast carcinoma has a great tendency to spread to the mandible. It is concomitantly associated with bone destruction, food intake disorder, and a poorer prognosis. Appropriate animal models need to be developed for a better understanding of the mechanisms underlying the metastatic process of breast cancer cells to mandible and to test the effects of potential lead compounds. Here, we assessed the metastasis model of intracardiac injection using luciferase-transfected metastatic breast cancer cells (MDA-MB-231Luc+) by determining the incidences of metastasis, mCT images, and histopathological results. A high bioluminescence signal mainly detected mandibular lesions with less frequent distal femora and proximal tibiae lesions. Extensive mandibular bone destruction occurred in nude mice grafted with metastatic breast cancer cells. This type of animal model might be a useful tool in assessing therapeutic implications and the efficacy of anti-cancer drugs for osteolytic cancers.

The anomalous canal between two accessory foramina on the mandibular ramus: the temporal crest canal

OBJECTIVES The temporal crest canal (TCC) is a variation of the bony canal with two accessory foramina that correspond to an entrance and an exit on the mandibular ramus. This study investigated the anatomical characteristics of the TCC using CBCT. METHODS The study population consisted 446 patients who had undergone CBCT. Sagittal, cross-sectional and three-dimensional images were evaluated for the presence of a TCC. The canals were classified into two types according to the configuration, and the location of the posterior accessory foramen of the TCC was also recorded. RESULTS 6 TCCs were present in 4 of 446 patients (0.90% of the total population). All of the TCCs were observed in males, and all of the posterior foramina were located superior to the mandibular foramina on the medial aspect of the mandibular ramus. There were five noticeably curved and increasingly narrow canals (Type 1) and one slightly curved and uniformly wide canal (Type 2). CONCLUSIONS Precise knowledge of the TCC is clinically important for suitable local anaesthetic nerve block and the planning of surgical procedures that involve the mandibular ramus. Three-dimensional images of CBCT data are particularly effective for confirming the presence of this variation.

Automatic analysis algorithm for acquiring standard dental and mandibular shape data using cone-beam computed tomography

This study aims to introduce a new algorithm developed using retrospective cone-beam computed tomography (CBCT) data to obtain a standard dental and mandibular arch shape automatically for an optimal panoramic focal trough. A custom-made program was developed to analyze each arch shape of randomly collected 30 CBCT images. First, volumetric data of the mandible were binarized and projected in the axial direction to obtain 2-dimensional arch images. Second, 30 patients’ mandibular arches were superimposed on the center of the bilateral distal contact points of the mandibular canines to generate an average arch shape. Third, the center and boundary of a panoramic focal trough were obtained using smoothing splines. As a result, the minimum thickness and transition of the focal trough could be obtained. If this new algorithm is applied to big data of retrospective CBCT images, standard focal troughs could be established by race, sex, and age group, which would improve the image quality of dental panoramic radiography.

Organized hematoma of temporomandibular joint

Organized hematoma is a pseudo-tumorous lesion mostly occurs at sinonasal cavity and often confused with malignant neoplasm. The initiation of this lesion is blood accumulation, probably due to trauma, and this hematoma develops into organized hematoma as it encapsulated with fibrous band and neo-vascularized. Since it is uninformed at temporomandibular joint (TMJ) region, imaging diagnosis might be challenging. Also, delayed detection of mass involving TMJ is not uncommon due to confusion with joint disorder. Thus, this report introduced the rare pathology, organized hematoma on TMJ with advanced imaging features. Also, diagnostic point for early detection was described for the TMJ tumors and pseudo-tumors considering complexity of surgical intervention in this region.

Morphological analysis of the lower second premolar for age estimation of Korean adults

OBJECTIVES This study aimed to examine the applicability of the pulp/tooth area ratio in the lower premolar teeth using panoramic radiography in age estimation of Korean adults. METHODS 402 digital panoramic images of Korean adults between 20 and 78 years were analyzed. Following Cameriere et al.s method, two observers measured the pulp and tooth areas of the lower second premolar on digital panoramic images, and the ratio of pulp to tooth area in the whole tooth (PTR) was calculated. In addition, the whole tooth was divided into coronal and root parts at the cementoenamel junction, and the ratios in the coronal part (PcCR) and root part (PrRR) were also calculated separately. Independent t-test, Analysis of covariance, linear regression, and the standard error of the estimate (SEE) were computed using statistical software. To justify the use of linear regression models for purposes of prediction, diagnostic tests of principal assumptions were also performed. RESULTS Independent t-test revealed significant differences in genders. PrRR produced the best age correlation (male, SEE=10.8; female, SEE=9.8; total, SEE=10.4 years), followed closely by PTR (male, SEE=11.1; female, SEE=10.3; total, SEE=10.7 years) and a relatively lower accuracy for PcCR (male, SEE=14.7; female, SEE=14.4; total, SEE=14.6 years). Model assumptions and accuracy for purposes of prediction in PTR and PrRR were satisfied. CONCLUSIONS The pulp/tooth area ratio using panoramic radiography has the potential as an effective tool for age estimation in the Korean adult population, and the pulp/tooth area ratio in the root part is more accurate than that of the whole tooth. Notably, female has shown higher accuracy compare to male subject.

Strut analysis for osteoporosis detection model using dental panoramic radiography

OBJECTIVES The aim of this study was to identify variables that can be used for osteoporosis detection using strut analysis, fractal dimension (FD) and the gray level co-occurrence matrix (GLCM) using multiple regions of interest and to develop an osteoporosis detection model based on panoramic radiography. METHODS A total of 454 panoramic radiographs from oral examinations in our dental hospital from 2012 to 2015 were randomly selected, equally distributed among osteoporotic and non-osteoporotic patients (n = 227 in each group). The radiographs were classified by bone mineral density (T-score). After 3 marrow regions and the endosteal margin area were selected, strut features, FD and GLCM were analysed using a customized image processing program. Image upsampling was used to obtain the optimal binarization for calculating strut features and FD. The independent-samples t-test was used to assess statistical differences between the 2 groups. A decision tree and support vector machine were used to create and verify an osteoporosis detection model. RESULTS The endosteal margin area showed statistically significant differences in FD, GLCM and strut variables between the osteoporotic and non-osteoporotic patients, whereas the medullary portions showed few distinguishing features. The sensitivity, specificity, and accuracy of the strut variables in the endosteal margin area were 97.1%, 95.7 and 96.25 using the decision tree and 97.2%, 97.1 and 96.9% using support vector machine, and these were the best results obtained among the 3 methods. Strut variables with FD and/or GLCM did not increase the diagnostic accuracy. CONCLUSION The analysis of strut features in the endosteal margin area showed potential for the development of an osteoporosis detection model based on panoramic radiography.

Change in Image Quality According to the 3D Locations of a CBCT Phantom.

A patient’s position changes in every CBCT scan despite patient alignment protocols. However, there have been studies to determine image quality differences when an object is located at the center of the field of view (FOV). To evaluate changes in the image quality of the CBCT scan according to different object positions, the image quality indexes of the Alphard 3030 (Alphard Roentgen Ind., Ltd., Kyoto, Japan) and the Rayscan Symphony (RAY Ind., Ltd., Suwon, Korea) were measured using the Quart DVT_AP phantom at the center of the FOV and 6 peripheral positions under four types of exposure conditions. Anterior, posterior, right, left, upper, and lower positions 1 cm offset from the center of the FOV were used for the peripheral positions. We evaluated and compared the voxel size, homogeneity, contrast to noise ratio (CNR), and the 10% point of the modulation transfer function (MTF10%) of the center and periphery. Because the voxel size, which is determined by the Nyquist frequency, was within tolerance, other image quality indexes were not influenced by the voxel size. For the CNR, homogeneity, and MTF10%, there were peripheral positions which showed considerable differences with statistical significance. The average difference between the center and periphery was up to 31.27% (CNR), 70.49% (homogeneity), and 13.64% (MTF10%). Homogeneity was under tolerance at some of the peripheral locations. Because the CNR, homogeneity, and MTF10% were significantly affected by positional changes of the phantom, an object’s position can influence the interpretation of follow up CBCT images. Therefore, efforts to locate the object in the same position are important.