• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.44-50
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• 2003

Design method for involute bevel gears is developed. The developed gear design system can design the optimized gear that minimize the number of pinion teeth with face tooth. Method of optimization is MS(matrix search) which is developed from this study. Design variables are pressure angle 20., transmitted power, gear volume, gear ratio, allowable contact stress and allowable bending stress. etc. Gears design method developed this study can be applied to the plane, helicopter, printer, machine tools.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.2
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• pp.238-247
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• 2021

Congenital tooth agenesis is the most common developmental dental anomaly, of which oligodontia is defined as the absence of six or more permanent teeth, except the third molars. Tooth agenesis causes malocclusion, alveolar atrophy, aesthetic and psychosocial problems. This clinical report describes a multidisciplinary treatment for a patient diagnosed as oligodontia, who exhibited absence of 14 permanent teeth, atrophy of maxillary alveolar bone, and mandibular protrusion. Restoration space was secured and tooth axis was improved by the extraction of deciduous teeth and orthodontic treatment. However, edge-to-edge bite of posterior teeth and arch dimension discrepancy due to atrophic maxilla was remained. To restore the aesthetics and functionality, implant retained prosthesis was planned. Considering minimal bone grafts, location and number of dental implants and prostheses design were determined. Through the gradual adjustment of provisional restoration, the appropriate centric and eccentric occlusion was reflected into a definitive prosthesis. Currently, stable functional results were attained, however, regular follow up and maintenance care over lifetimes should be performed.

• Journal of Oral Medicine and Pain
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• v.36 no.4
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• pp.215-224
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• 2011

The aim of the study was to investigate the effects of 904 nm GaAs laser irradiation for patients with hypersensitive teeth and to find the possibility of clinical use of this Low Level Laser Therapy (LLLT) for the control of hypersensitive teeth. Eleven patients visited Dept. of Oral Medicine, Dankook University participated in this study. Each patient contributed at least two or more contralateral pairs of hypersensitive teeth with exposed dentine at cervical surfaces. Total number of teeth used from subjects participated in this study was 50: 25 experimental and control teeth respectively. All participants were treated with 904 nm GaAs diode laser every week during 4 weeks. Tactile and cold (ice stick) tests were carried out before LLLT every week during 4 weeks and 1 week later after the last LLLT by measuring visual analogue scale (VAS) of patients and by measuring a score of electrical pulp tester (EPT) simultaneously. The VAS score in tactile test decreased significantly with time, but there was not statistically difference between those of groups. The score of EPT in the experimental group was significantly higher than that of control group, although there was no change with time. In cold test, there was significant difference between two groups and cold sensitivity of the experimental group significantly decreased with time after every LLL irradiation, compared with that of control group. Based on the results, it is suggested that the 904 nm GaAs laser irradiation could be positively used as an effective, reversible method in treating cervical dentine hypersensitivity.

• Journal of Technologic Dentistry
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• v.42 no.1
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• pp.1-8
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• 2020

Purpose: Among the virtual teeth generated by Deep Convolutional Generative Adversarial Networks (DCGAN), the optimal data was analyzed for the number of learning. Methods: We extracted 50 mandibular first molar occlusal surfaces and trained 4,000 epoch with DCGAN. The learning screen was saved every 50 times and evaluated on a Likert 5-point scale according to five classification criteria. Results were analyzed by one-way ANOVA and tukey HSD post hoc analysis (α = 0.05). Results: It was the highest with 83.90±6.32 in the number of group3 (2,050-3,000) learning and statistically significant in the group1 (50-1,000) and the group2 (1,050-2,000). Conclusion: Since there is a difference in the optimal virtual tooth generation according to the number of learning, it is necessary to analyze the learning frequency section in various ways.

• International Journal of Oral Biology
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• v.36 no.1
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• pp.37-42
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• 2011

The working mechanism of bisphosphonate on bone cells is unclear despite its powerful inhibitory activity on bone resorption. The differentiation and activation of osteoclasts are essential for bone resorption and are controlled by the stimulatory RANKL and inhibitory OPG molecules. Teeth exhibit a range of movement patterns during their eruption to establish their form and function, which inevitably accompanies peripheral bone resorption. Hence, the mandible, which contains the teeth during their eruption processes, is a good model for revealing the inhibitory mechanism of bisphosphonate upon bone resorption. In the present study, RANKL and OPG expression were examined immunohistochemically in the mandible of rats with developing teeth after alendronate administration (2.5 mg/kg). The preeruptive mandibular first molars at postnatal days 3 to 10 showed the developing stages from bell to crown. No morphological changes in tooth formation were observed after alendronate administration. The number of osteoclasts in the alveolar bone around the developing teeth decreased markedly at postnatal days 3, 7 and 10 compared with the control group. RANKL induced strong positive immunohistochemical reactions in the dental follicles and stromal cells around the mandibular first molar. In particular, many osteoclasts with strongly positive reactions to RANKL appeared above the developing mandibular first molars at postnatal days 3 and 10. Immunohistochemical reactions with RANKL after alendronate administration were weaker than the control groups. However, the immunohistochemical reactivity to OPG was stronger after alendronate administration, at postnatal days 3 and 10. These results suggest that alendronate may decrease bone resorption by regulating the RANKL/OPG pathway in the process of osteoclast formation, resulting in a delay in tooth eruption.

• Journal of Korean society of Dental Hygiene
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• v.9 no.3
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• pp.426-438
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• 2009

The purpose of this study was to examine the relationship of the general characteristics of dental patients to their total O'Leary index and individual plaque indexes in a bid to check the oral hygiene state of citizens and evaluate their plaque management ability. The subjects in this study were 288 patients at dental hospitals and clinics in Busan and South Gyeongsang Province. A survey was conducted from September to November 2008. The findings of the study were as follows: 1. Overall, the O'Leary index of the patients investigated stood at 72 percent. By age and gender, the O'Leary index was highest among those in their 30s(83%) and among the women(75%)(p<.05). As to the influence of toothbrushing frequency, the patients who did it twice or more a day had the highest O'Leary index(75%)(p<.001). By the use of oral hygiene supplies, the patients who used oral hygiene supplies had a higher O'Leary index(76%) than the others who didn't(p<.01). 2. As for plaque index for each tooth, 28 percent of their teeth were given zero point, and 52 percent were given one mark. 13 percent were given two marks, and 6.3 percent were given three marks. Thus, the teeth that were given one mark were largest in number(p<.001). 3. As for plaque index for labial posterior mandibular, 43 percent of their teeth were given one point, and 36 percent were given zero mark. 14 percent were given three mark, and 5 percent were given three marks(p<.01). 4. As for plaque index for buccal posterior maxilla, 57 percent of their teeth were given one point, and 20 percent were given zero mark. 16 percent were given two mark, and 6.3 percent were given three marks(p<.01). 5. As for plaque index for lingual posterior mandibular, 56 percent of their teeth were given one point, and 27.8 percent were given zero mark. 9 percent were given three mark and 6 percent were given three mark(p<.001).

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.88-94
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• 2019

PURPOSE. This study was conducted to investigate patterns of adjacent tooth displacement in the posterior implant with interproximal contact loss (ICL) by 3-D digital superimposition method. MATERIALS AND METHODS. Posterior partially edentulous patients, restored with implant fixed partial prostheses before 2011 and suffered from food impaction of ICL between 2009 and 2011, were included. Two dental casts, at the time of delivery and at the time of food impaction in a same patient, was converted into 3-D digital models through scanning and superimposition was performed to assess chronologic changes of the dentition. Directions of tooth displacement were evaluated and the amount of ICL was calculated. Correlations between the amount of ICL and elapsed time, or between the amount of ICL and age after function, were assessed at a significance level of P<.05. RESULTS. A total number of 13 patients (8 males, 5 females) with a mean age of $65.76{\pm}9.94years$ and 17 areas (4 maxillae, 13 mandibles) were included in this retrospective study. Teeth adjacent to the implant restoration showed complex displacements but characteristic tendency according to the location of the arch. The mean amount of ICL was $0.33{\pm}0.14mm$. Elapsed time from function to ICL was $61.47{\pm}31.27months$. There were no significant differences between the amount of ICL and elapsed time, or age (P>.05). CONCLUSION. Natural teeth showed various directional movements to result in occlusal change in the arch. The 3-D superimposition of chronologic digital models was a helpful method to analyze the changes of dentition and individual tooth displacement adjacent to implant restoration.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.3
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• pp.556-561
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• 1997

Intentional replantation of the posterior teeth has been performed as a last resort except extraction when it is impossible to perform the conventional endodontic or surgical endodontic treatment. Many studies have done with the prognosis, and root resorption, of which the responsibility might have been injury of periodontal ligament and remaining periodontal lesion, proved to be major cause of failure. Intentional replantation, however, can exclude anatomic difficulty, risk of nerve injury, and maxillary sinus trauma that surgical access can raise, especially in posterior teeth, and it is reported that success rate is not less than surgical endodontics, independent of replantation of traumatically avulsed teeth. The success of intentional replantation can be evaluated with, clinically, reduction of pocket depth, pain and mobility(physical mobility), and, radiographically, hard tissue formation, reduction of periapical radiolucency. In this case report, for the maxillary left first bicuspid with dens evaginatus that had periapical lesion, painfulness, mobility and showed no reduction of mobility after even extirpation and a number of irrigation, extraction followed by extraoral root filling with calcium hydroxide and replantation was performed. Based on many studies, it is concluded that hard tissue formation capacity of calcium hydroxide, preceded extirpation before extraction, and careful extraction without injuring periodontal ligament affected successful results of this case.

• Journal of Periodontal and Implant Science
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• v.23 no.2
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• pp.352-357
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• 1993

The purpose of the present study was to evaluate and compare the periodontal conditions of distally extending cantilever bridges(CB) and removable patial dentures(RPD). 78 patients treated with removable partial dentures were divided into 2 groups; bilateral free-ending (type 1) and unilateral free-ending(type 2). 43 patients treated with distally extending cantilever bridges were divided into 4 groups according to position of missing molars and number of including abutment tooth (or teeth) (type 1-4). Prosthodontic status of the abutment teeth were assessed; overcontoured crown, overhanged margin, embrasure closure, and others. Their Periodonted status were assessed with Plaque Index Gingial Index(GI) Sulcus bleedy Index (SBI), Tooth mobility(TM) & Posher depth(PPD). 35.9% of RPD group and 38.1 of CB grouphad disconfort on mastication with prosthetics. 16.7% of RPD group and 6.1% of CB group showed on opposing sites. Overhanged margins were 58.3% for RPD group and 86.6% for GB group. 45.5% of RPD group and 72% of CB group had embrasure closure on the abutment teeth. 30.5% of GB group had oversized pontic. Gb group showed much higher clinical parameters than RPD groups, but statistically not significant. Type 2 of RPD group showed lower GI and SBI, but statistically not significant. Type 3 of CB group showed the highest GI and SBI and type 2 showed the highest tooth mobility, but there is no differences between the same type of groups. In conclusion, only minor differences in periodontal conditions were recorded in RPD and CB group.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.2
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• pp.323-336
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• 1996

This is a retrospective study on the patients with infection of the oral and maxillofacial region with the purpose of obtaining some useful data for diagnosis and treatment plan of that relatively common disease in dentistry. The used materials of study were 87 in total, including 52 male patients, 35 female patients who diagnosed and treated at the Department of the Dentistry in Hanyang Medical College Hospital for the period of Jan. 1990 to Dec. 1994. The author analyzed the distribution and incidence of sex, age, admission period, etiologic factors, etiologic teeth, treatment method of infections, pus culture, antibiotics sensibilities and medication. The result obtained as follows : 1. The developmental incidences by sex was superior in male by the ratio of 1.5 : 1 and the infection was most frequently occurred during the third decades(35.6%). 2. The number of admitted patients elevated in February, March, and April, and average of admission period was 9.8 days. 3. Main etiologic teeth showed on lower molar region in adult(63%) and upper molar region in primary dentition(46.1%). 4. Medications were administrated in all of the cases, and surgical incision and drainage were performed in 53% and extraction of the causative teeth were performed in 63.6% of all cases. 5. The most common involved fascial spaces were Buccal space(41.4%), Infraorbital space(27.6%), Submandibular space(16.1%),in order, and 9 cases(10.3%) were Ludwig's Angina. In 68.2% of the patients, and infection involved only one fascial space and in 21.8% of the patients, it involved to more fascial spaces. 6. The most causative organisms isolated from pus culture were Gram-positive facultative cocci(55.5%), and antibiotics sensitivities on the total isolated bacterial strains were exposed chloramphenicol(88.6%), Cephalothin(88.6%), Erythromycin(81.5%), Lincomycin(77.8%) in order, but it showed resistant on Gentamycin(58.3%), Tetracycline(56.5%), Methicillin(38.5%).