Accessory mental foramina associated with neurovascular bundle in Korean population.

PURPOSE: To determine the prevalence and anatomical features of accessory mental foramina (AMFs) associated with neurovascular bundle using reformatted CBCT images in Korean population. MATERIALS AND METHODS: Three-dimensional, cross-sectional, and axial images of CBCT from total 446 patients were evaluated. To include only AMF associated with neurovascular bundle, the course of accessory nerve through AMF was evaluated on three-dimensional images. The prevalence, locations to mental foramen (MF), and distribution to the adjacent tooth of AMF were analyzed. Additionally, the distance from MF and dimension of AMF were measured. RESULTS: AMFs were found in 36 (8.1 %) patients in the 446 Koreans. The prevalence rate of AMFs in male was significant higher than that in female (p < 0.05). Most AMFs were located anterior-superior to MF. The shortest distance between the center of AMF and that of MF was 5.80 mm (SD ± 2.90, 1.40-13.0). Variance of location of AMF in relation to MF was greater in the horizontal direction than in the vertical direction. In related to adjacent tooth, AMF was mainly distributed between the first and second premolars. The horizontal dimension and vertical dimension of AMF were 1.54 mm (SD ± 1.41, 0.70-9.80) and 1.44 mm (SD ± 0.41, 0.70-2.30), respectively. CONCLUSIONS: Knowledge of AMF is important for performing effective nerve block and avoiding injuries to neurovascular bundles passing through AMF. Evaluation of the course of AMF in three-dimensional image of CBCT is effective for confirming AMF associated with inferior alveolar nerve.

Detecting 17 fine-grained dental anomalies from panoramic dental radiography using artificial intelligence.

Panoramic dental radiography is one of the most common examinations performed in dental clinics. Compared with other dental images, it covers a wide area from individual teeth to the maxilla and mandibular area. Dental clinicians can get much information about patients' health. However, it is time-consuming and laborious to detect all signs of anomalies because these regions are very complicated. So it is needed to filter out healthy images to save clinicians' time to examine. For this, we applied modern artificial intelligence-based computer vision techniques. In this study, we built a model to detect 17 fine-grained dental anomalies which are critical to patients' dental health and quality of life. We used about 23,000 anonymized panoramic dental images taken from local dental clinics from July 2020 to July 2021. Our model can detect these abnormal signs and filter out normal images with high sensitivity of about 0.99. The result indicates that our model can be used in real clinical practice to alleviate the burden of clinicians.

Comparison of detection performance of soft tissue calcifications using artificial intelligence in panoramic radiography.

Artificial intelligence (AI) is limited to teeth and periodontal disease in the dental field, and is used for diagnosis assistance or data analysis, and there has been no research conducted in actual clinical situations. So, we created an environment similar to actual clinical practice and conducted research by selecting three of the soft tissue diseases (carotid artery calcification, lymph node calcification, and sialolith) that are difficult for general dentists to see. Therefore, in this study, the accuracy and reading time are evaluated using panoramic images and AI. A total of 20,000 panoramic images including three diseases were used to develop and train a fast R-CNN model. To compare the performance of the developed model, two oral and maxillofacial radiologists (OMRs) and two general dentists (GDs) read 352 images, excluding the panoramic images used in development for soft tissue calcification diagnosis. On the first visit, the observers read images without AI; on the second visit, the same observers used AI to read the same image. The diagnostic accuracy and specificity for soft tissue calcification of AI were high from 0.727 to 0.926 and from 0.171 to 1.000, whereas the sensitivity for lymph node calcification and sialolith were low at 0.250 and 0.188, respectively. The reading time of AI increased in the GD group (619 to 1049) and decreased in the OMR group (1347 to 1372). In addition, reading scores increased in both groups (GD from 11.4 to 39.8 and OMR from 3.4 to 10.8). Using AI, although the detection sensitivity of sialolith and lymph node calcification was lower than that of carotid artery calcification, the total reading time of the OMR specialists was reduced and the GDs reading accuracy was improved. The AI used in this study helped to improve the diagnostic accuracy of the GD group, who were not familiar with the soft tissue calcification diagnosis, but more data sets are needed to improve the detection performance of the two diseases with low sensitivity of AI.

Access opening guide produced using a 3D printer (AOG-3DP) as an effective tool in difficult cases for dental students.

OBJECTIVES: The aim of this study was to determine the effectiveness of using an access opening guide in teaching ideal access opening shape and preventing excessive tooth loss, with a focus on predoctoral dental students. METHODS: Ninety teeth that were mounted in a box just below the level of the cementoenamel junction using tray resin were randomly divided into two study groups. An access opening guide produced using a 3D printer (AOG-3DP) was designed using cone-beam computed tomography (CBCT). The AOG-3DP was applied in the test groups, while no aid was used in the control group. Access preparations in both groups performed by predoctoral dental students were scanned using CBCT to detect overpreparation. The preparation time and access cavity volume were evaluated. RESULTS: The mean times required for achieving access opening were 327.2 and 97.4 s in the control and AOG-3DP groups, respectively, for premolars, and 547.4 and 104.5 s for molars. The mean volumes for premolars and molars differed from the ideal cavities by 38.1 and 72.2 mm3 , respectively, in the control group, and by -2.0 and -8.7 mm3 the AOG-3DP group. CONCLUSIONS: Using the AOG-3DP significantly reduced the access opening time for premolars and molars. However, there is a limitation in that CBCT DICOM images must be converted to stereolithographic .stl files in order to be printed via 3D technology. This requires additional preclinical treatment time for imaging and subsequent printing. It could be considered that this can be a useful method in difficult cases.

Osteoporosis detection in panoramic radiographs using a deep convolutional neural network-based computer-assisted diagnosis system: a preliminary study.

OBJECTIVES: To evaluate the diagnostic performance of a deep convolutional neural network (DCNN)-based computer-assisted diagnosis (CAD) system in the detection of osteoporosis on panoramic radiographs, through a comparison with diagnoses made by oral and maxillofacial radiologists. METHODS: Oral and maxillofacial radiologists with >10 years of experience reviewed the panoramic radiographs of 1268 females {mean [± standard deviation (SD)] age: 52.5 ± 22.3 years} and made a diagnosis of osteoporosis when cortical erosion of the mandibular inferior cortex was observed. Among the females, 635 had no osteoporosis [mean (± SD) age: 32.8 ± SD 12.1 years] and 633 had osteoporosis (72.2 ± 8.5 years). All panoramic radiographs were analysed using three CAD systems, single-column DCNN (SC-DCNN), single-column with data augmentation DCNN (SC-DCNN Augment) and multicolumn DCNN (MC-DCNN). Among the radiographs, 200 panoramic radiographs [mean (± SD) patient age: 63.9 ± 10.7 years] were used for testing the performance of the DCNN in detecting osteoporosis in this study. The diagnostic performance of the DCNN-based CAD system was assessed by receiver operating characteristic (ROC) analysis. RESULTS: The area under the curve (AUC) values obtained using SC-DCNN, SC-DCNN (Augment) and MC-DCNN were 0.9763, 0.9991 and 0.9987, respectively. CONCLUSIONS: The DCNN-based CAD system showed high agreement with experienced oral and maxillofacial radiologists in detecting osteoporosis. A DCNN-based CAD system could provide information to dentists for the early detection of osteoporosis, and asymptomatic patients with osteoporosis can then be referred to the appropriate medical professionals.

Effect of decompression for patients with various jaw cysts based on a three-dimensional computed tomography analysis.

OBJECTIVES: The aim of this study is to evaluate the effectiveness of decompression according to reduction parameters by measuring cystic volume changes using computed tomography (CT). STUDY DESIGN: We chose patients who had undergone decompression for a cystic lesion of the jaw at the Department of Oral and Maxillofacial Surgery in our dental hospital between 2006 and 2015. All patients had been examined by CT before and after decompression. We measured the volume of cystic lesions using the threshold method and evaluated the volumetric changes after decompression according to various parameters. RESULTS: The mean reduction rates of 46 cystic cases was 57.95%. There was a statistically significant difference in reduction rates by initial volume; the group with large initial volume reported higher reduction rates. CONCLUSION: Decompression is more effective in larger initial lesions when carried out more than 6 months. CT is an efficient method for evaluating the bony healing within the cyst cavity by measuring changes in cystic volume after decompression. However, due to its high cost and radiation dose, a comparative study using another diagnostic radiographic tool should be considered.

Risk factors of osteonecrosis of the jaw after tooth extraction in osteoporotic patients on oral bisphosphonates.

PURPOSE: The aim of this study was to investigate the incidence of bisphosphonate-related osteonecrosis of the jaw (BRONJ) after tooth extraction in patients with osteoporosis on oral bisphosphonates in Korea and to evaluate local factors affecting the development of BRONJ. MATERIALS AND METHODS: The clinical records of 320 patients who underwent dental extraction while receiving oral bisphosphonates were reviewed. All patients had a healing period of more than 6 months following the extractions. Each patient's clinical record was used to assess the incidence of BRONJ; if BRONJ occurred, a further radiographic investigation was carried out to obtain a more definitive diagnosis. Various local factors including age, gender, extraction site, drug type, duration of administration, and C-terminal telopeptide (CTx) level were retrieved from the patients' clinical records for evaluating their effect on the incidence of BRONJ. RESULTS: Among the 320 osteoporotic patients who underwent tooth extraction, 11 developed BRONJ, reflecting an incidence rate of 3.44%. Out of the local factors that may affect the incidence of BRONJ, gender, drug type, and CTx level showed no statistically significant effects, while statistically significant associations were found for age, extraction site, and duration of administration. The incidence of BRONJ increased with age, was greater in the mandible than the maxilla, and was associated with a duration of administration of more than 3 years. CONCLUSION: Tooth extraction in patients on oral bisphosphonates requires careful consideration of their age, the extraction site, and the duration of administration, and close postoperative follow-up should be carried out to facilitate effective early management.

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.

Eruption of posterior teeth in the maxilla and mandible for age determination of water deer.

OBJECTIVE: Eruption of posterior teeth, including premolars and molars in the mandible rather than in the maxilla, is accepted as an accurate reference for age determination of deer. In water deer, Hydropotes inermis, the eruption age of mandibular molars has been described in two studies, but the ages were inconsistent with each other. In this study, we aimed to confirm the eruption age of mandibular posterior teeth for the accurate age determination of water deer and to evaluate the efficacy of maxillary posterior teeth for the age determination of deer. DESIGN: The eruption of mandibular and maxillary posterior teeth was investigated in the dry skulls of individual wild water deer of both sexes, up to an age of about 15 months. RESULTS: The eruption age of mandibular molars in water deer was consistent with that of a previous study. The eruption age of posterior teeth was almost the same in the maxilla and mandible of individual water deer. The deciduous mandibular fourth premolar and the permanent maxillary fourth premolar were two easiest teeth to be identified for the age determination. CONCLUSIONS: The former controversial eruption age of mandibular posterior teeth in water deer was confirmed. Our study first presented the eruption age of maxillary posterior teeth in water deer. It is suggested that posterior teeth not only in the mandible but also in the maxilla are useful indicators for the age determination of water deer.

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.

Mandibular metastasis of cholangiocarcinoma: A case report.

Tumors metastasizing from distant regions to the oral and maxillofacial region are uncommon, comprising only 1%-2% of all malignancies. Cholangiocarcinoma is a malignancy that arises from cholangiocytes, which are epithelial cells that line the bile ducts. These cancers are difficult to diagnose and have a poor prognosis. In this paper, we report a rare case of mandibular metastasis of cholangiocarcinoma diagnosed at the primary site and discuss the radiographic findings observed in this case.

Effect of mandibular positioning on preimplant site measurement of the mandible in reformatted CT.

The purpose of this study was to evaluate the effect of mandibular positioning on measurement of the reformatted cross-sectional image of the mandible in computed tomography (CT) according to the area on the mandible. Five dried mandibles, partially edentulous in the premolar and molar areas, were selected. The inferior border of the mandible was placed at 0-, 5-, 10-, 15-, and 20-degree angles to the CT scanning plane, and CTs were taken. The marked area of the reformatted cross-sectional image taken at each angle was found, and the distance from the most superior border of the mandibular canal to the alveolar crest was measured. As the angle between the CT scanning plane and mandibular plane increased, the distance from the most superior border of the mandibular canal to the alveolar crest also increased. The degree of increase was more pronounced in the posterior portion of the mandible than in the anterior portion of the mandible. As mandibular positional change in the CT gantry can affect the vertical measurement of the reformatted cross-sectional image, a correct guiding plane is necessary to accurately position the jaw to the CT scanning plane.

Factors influencing superimposition error of 3D cephalometric landmarks by plane orientation method using 4 reference points: 4 point superimposition error regression model.

Superimposition has been used as a method to evaluate the changes of orthodontic or orthopedic treatment in the dental field. With the introduction of cone beam CT (CBCT), evaluating 3 dimensional changes after treatment became possible by superimposition. 4 point plane orientation is one of the simplest ways to achieve superimposition of 3 dimensional images. To find factors influencing superimposition error of cephalometric landmarks by 4 point plane orientation method and to evaluate the reproducibility of cephalometric landmarks for analyzing superimposition error, 20 patients were analyzed who had normal skeletal and occlusal relationship and took CBCT for diagnosis of temporomandibular disorder. The nasion, sella turcica, basion and midpoint between the left and the right most posterior point of the lesser wing of sphenoidal bone were used to define a three-dimensional (3D) anatomical reference co-ordinate system. Another 15 reference cephalometric points were also determined three times in the same image. Reorientation error of each landmark could be explained substantially (23%) by linear regression model, which consists of 3 factors describing position of each landmark towards reference axes and locating error. 4 point plane orientation system may produce an amount of reorientation error that may vary according to the perpendicular distance between the landmark and the x-axis; the reorientation error also increases as the locating error and shift of reference axes viewed from each landmark increases. Therefore, in order to reduce the reorientation error, accuracy of all landmarks including the reference points is important. Construction of the regression model using reference points of greater precision is required for the clinical application of this model.