• Imaging Science in Dentistry
• /
• v.50 no.2
• /
• pp.169-174
• /
• 2020

Purpose: Periodontal disease causes tooth loss and is associated with cardiovascular diseases, diabetes, and rheumatoid arthritis. The present study proposes using a deep learning-based object detection method to identify periodontally compromised teeth on digital panoramic radiographs. A faster regional convolutional neural network (faster R-CNN) which is a state-of-the-art deep detection network, was adapted from the natural image domain using a small annotated clinical data- set. Materials and Methods: In total, 100 digital panoramic radiographs of periodontally compromised patients were retrospectively collected from our hospital's information system and augmented. The periodontally compromised teeth found in each image were annotated by experts in periodontology to obtain the ground truth. The Keras library, which is written in Python, was used to train and test the model on a single NVidia 1080Ti GPU. The faster R-CNN model used a pretrained ResNet architecture. Results: The average precision rate of 0.81 demonstrated that there was a significant region of overlap between the predicted regions and the ground truth. The average recall rate of 0.80 showed that the periodontally compromised teeth regions generated by the detection method excluded healthiest teeth areas. In addition, the model achieved a sensitivity of 0.84, a specificity of 0.88 and an F-measure of 0.81. Conclusion: The faster R-CNN trained on a limited amount of labeled imaging data performed satisfactorily in detecting periodontally compromised teeth. The application of a faster R-CNN to assist in the detection of periodontally compromised teeth may reduce diagnostic effort by saving assessment time and allowing automated screening documentation.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.34 no.3
• /
• pp.498-505
• /
• 2007

Management options for impacted maxillary canines can include (1) continued observation, (2) extraction of the primary canine to aid spontaneous eruption, (3) uncovering and bonding of the impacted tooth and its eruption using orthodontic traction, (4) autotransplantation, and (5) extraction followed by prosthetic replacement. Autotransplantation should be considered when the degree of malposition is too severe to correct by orthodontic alignment. The present report describes the management of an ectopic eruption of the left maxillary canine in an 10-year-old girl. The treatment included the extraction of primary maxillary left canine and the autotransplantation using a Rapid Prototyping model. By using RP model to contour the recipient bone and check for fitting in the prepared socket, the extra-oral time can reduce. The autotransplanted canine showed mobility within normal limit, negative response to percussion and positive to electric pulp test after 6 months.

• Applied Biological Chemistry
• /
• v.41 no.6
• /
• pp.431-436
• /
• 1998

The optimum ohmic heating condition of apple juice was investigated with model solution. The temperature rise of model solution was found to be $7.8,\;21.0,\;47.4^{\circ}C/min$ when the distances between electrodes were 29, 22, and 17mm, respectively. The heating rate increased proportionally with the numbers of electrode pairs, 1 to 3 and highly dependent on applied voltage. The heating rate was not affected by the frequencies ranged from 60 Hz to 60 KHz and the wave form of applied alternating electric current. The apple juices prepared by ohmic heating sterilization revealed similar physicochemical properties to that by commercial sterilization.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.19 no.1
• /
• pp.7-15
• /
• 2003

This study used FEM(Finite Element method) based on micro-CT images to see the effects of occlusal force distribution with varying bone density and structure. the mandibular premolar region from human cadaver, thickness of 10mm was imaged using micro-CT. the cross sectional images were taken every $10{\mu}m$. these were reconstructed and the longitudinal image at the mid point of mesiodistal of the speciman was obtained for the specimen for the FEM. The stress disribution produced by a vertical force at 100N and 100N horizontal were analyzed by MSC Nastran FEM Package. according to the result of this study the occlusal force distribution depends on the structure of cancellus bone and for further information on the occlusal force distribution on the tooth and the surrounding structure requires further studies on cancellus bone structure. CEJ of all model show the highest peak and region whice meet teeth and bone show second high peak. Original model and cortical bone add model show different stress distribution. Stress distribution changed according to bone structures and densities.

• Journal of Korean society of Dental Hygiene
• /
• v.11 no.5
• /
• pp.603-613
• /
• 2011

Objectives : This study is to investigate factors that predispose the oral health education patterns of teachers at preschool institutions such as kindergartens and day nurseries, for which a comparison was made among the patterns, whereto the PRECEDE model was applied. Methods : A survey was conducted by two visits, a preliminary survey and a main survey, and teachers at the foregoing institutions personally filled in the questionnaire. Results : 1. With relation to epidemiological and social diagnosis, the largest number of respondents (53.7%) agreed on the need for oral health education, but at the same time, the largest number of respondents (40.3%) was unsatisfactory with oral health education given by them. 2. With relation to behavioral diagnosis, there were many cases where respondents taught their students to brush their teeth after meals and snacks. Oral health education was focused on safety and injuries. There was no significant intergroup difference (p>0.05). 3. Predisposing factors (a subcategory of educational diagnosis) showed the following results: As for the frequency of oral health education, most respondents at both institutions answered preferred once every six month (p>0.05). In the case of oral health checkup, 75.4% of respondents at kindergartens preferred once a year. 72.2% of respondents at day nurseries preferred the same frequency. They showed a statistically significant difference (p<0.05). In enabling factors, it was found that most respondents at both institutions collected information and teaching materials from mass media and public health centers respectively. In enabling factors, insufficient teaching materials, media and knowledge were found to be obstacles to oral health education. Conclusions : Oral healthcare providers' cooperation is required to diversify away from tooth brushing-centered education and to enrich oral health education. In addition, continuous supplements are required to make teachers at preschool institutions acquire expert knowledge and give oral health education with confidence. Moreover, it needs to train them for various education programs as well as to support them with educational media. Lastly, family members' cooperation is required to develop oral health education programs.

• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.5
• /
• pp.633-643
• /
• 2007

Statement of problem: Recently there are on an increasing trend of using implants-especially in edentulous mandible of severly alveolar bone recessed. Purpose: The aim of this study was to analyze the displacement and stress distribution of various mandibular implant-retained overdenture models supported by two implants in interforaminal region under the occlusion scheme load. Material and method: FEA models were made by the 3D scanning of the edentulous mandibular dentiform. The three models were named as Model M1, M2, and M3 accord ing to the position of implants: M1, Lt. incisor area, M2, Canine area, and M3, 1st Premolar area. Inter-implant angulation model was named as M4. Conventional complete denture was named M5 and used as a control group. Ball implant and Gold matrice were used as a retentive anchors. The occlusion type loads were applied horizontally over each tooth. Results: 1. In mandibular implant retained overdenture Canine Protected Occlusion type load resulted in higher levels of stress to the implants and female matrices than other types of loads. 2. The overdenture model M1, with implants in lateral incisor areas resulted in lower stress concentration to the implants and female matrices than other models. 3. In mandibular implant retained overdenture the stresses of the implant and female matrice were lower in mesially inclined implant than these of parallel installed implant. Conclusion: Lateral incisor areas could be the best site for the implants in mandibular implant-retained overdenture. The mandibular implant retained overdenture models mentioned above showed to the lowest stress to the implants and female matrices.

• The korean journal of orthodontics
• /
• v.45 no.3
• /
• pp.113-120
• /
• 2015

Objective: This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing. Methods: Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models. Results: Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078). Conclusions: In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.12
• /
• pp.44-53
• /
• 2021

As environmental issues have emerged worldwide, emission gas regulations have been strengthened. In the construction machinery sector, studies have been actively conducted to utilize the power source of electric motors owing to the increasing demand for zero emissions. In this study, the gear specifications of an electric axle for construction machinery were selected by considering the specifications of the motor, gear tooth contact pattern, and face load factor. The gear strength evaluation was performed at the system level using the simulation model. The bending and contact strength of the spiral bevel gears and the bending strength of the planetary gear set showed a safety factor of 1 or more. However, the contact strength of the planetary gear set showed a safety factor of 0.92. Conservative results were derived by performing the analysis under the rated load condition of the motor. However, the ratio of the equivalent torque to the rated torque of the motor was 45% or less, hence, it was determined that no difficulties should arise regarding the durability of the axle.

• International Journal of Molecular Medicine
• /
• v.44 no.1
• /
• pp.125-134
• /
• 2019

Mutations in myelin protein zero (MPZ) cause inherited peripheral neuropathies, including Charcot-Marie-Tooth disease (CMT) and Dejerine-Sottas neuropathy. Mutant MPZ proteins have previously been reported to cause CMT via enhanced endoplasmic reticulum (ER) stress and Schwann cell (SC) death, although the pathological mechanisms have not yet been elucidated. In this study, we generated an in vitro model of rat SCs expressing mutant MPZ (MPZ V169fs or R98C) proteins and validated the increase in cell death and ER stress induced by the overexpression of the MPZ mutants. Using this model, we examined the efficacy of 3 different aminosalicylic acids (ASAs; 4-ASA, sodium 4-ASA and 5-ASA) in alleviating pathological phenotypes. FACS analysis indicated that the number of apoptotic rat SCs, RT4 cells, induced by mutant MPZ overexpression was significantly reduced following treatment with each ASA. In particular, treatment with 4-ASA reduced the levels of ER stress markers in RT4 cells induced by V169fs MPZ mutant overexpression and relieved the retention of V169fs mutant proteins in the ER. Additionally, the level of an apoptotic signal mediator (p-JNK) was only decreased in the RT4 cells expressing R98C MPZ mutant protein following treatment with 4-ASA. Although 4-ASA is known as a free radical scavenger, treatment with 4-ASA in the in vitro model did not moderate the level of reactive oxygen species, which was elevated by the expression of mutant MPZ proteins. On the whole, the findings of this study indicate that treatment with 4-ASA reduced the ER stress and SC death caused by 2 different MPZ mutants and suggest that ASA may be a potential therapeutic agent for CMT.

• The Journal of Korean Academy of Prosthodontics
• /
• v.52 no.4
• /
• pp.305-311
• /
• 2014

Purpose: When the full veneer crown was treated in the tooth with abfraction lesion due to various causes, the prognosis of it may be compromised according to the location of the finish line, but there is few study about the location of its buccal finish line. The purpose of this study was to investigate the effect of location of the finish line of the full veneer crown on stress distribution of the tooth with abfraction lesion. Materials and methods: The two dimensional finite element model was developed to express tooth, surrounding tissue and full veneer crown. The stress distribution under eccentric 144 N occlusal load was analyzed using finite element analysis. The location of finish line was set just at the lower border of the lesion (Group 0), 1 mm (Group 1) and 2 mm (Group 2) below the lower border of the lesion. Results: In the Group 0, von Mises stress was concentrated at the finish line and the apex of the lesion. Also, the stress at the bucal finish line propagated to the lingual side. In the Group 1 and Group 2, stress distribution was similar each other. Stress was concentrated at the apex of lesion, but the stress at the buccal finish line did not propagate to the lingual side. That implied decrease of the possibility of horizontal crown fracture. Conclusion: Full veneer crown alleviated the stress concentrated at the apex of the abfraction lesion, when the finish line of full veneer crown was set below the lower border of abfraction lesion.