• Restorative Dentistry and Endodontics
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• v.5 no.1
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• pp.47-51
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• 1979

Fifty two human mandibular second molars were chosen to study the anatomy of the root canal. The experimental teeth were injected with china ink, decalcified, cleared and used in study, in vitro, to determine the number of root, the number of root canals, canals per root, frequency and location of transverse anastomoses, frequency and location of lateral canals and frequency of the apical deltas. The results were as follows; 1. Most of the teeth showed three canals, but 19.2% of the teeth were found to have two canals and 9.6% of them four canals. 2. In so far as observing two canals per root, 80.8% of the teeth were found to have two canals in mesial root and 9.6% of them in distal canal. 3. In roots with, two canals, the seperated apical foramen appeared in 59.5% in mesial side and 40.0% in distal side, and the common apical foramen appeared in 40.5% in mesial side and 60.0% in distal side. 4. Of the two root canals in one root, 36.2% of the canals were found to have transverse anastomoses and were usually located in the apical third of the root. 5. 23.1% of 52 teeth were found to have lateral canals, and ramifications were mainly located in the apical third of the root.

• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.209-223
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• 2001

At intrusion of upper anterior teeth in patient with periodontal defect, the use of three-piece base arch appliance for pure intrusion is required. To investigate the change of the center of resistance and of the distal traction force according to alveolar bone height at intrusion of upper anterior teeth using this appliance, three-dimensional finite element models of upper six anterior teeth, periodontal ligament and alveolar bone were constructed. At intrusion of upper anterior teeth by three-piece base arch appliance, the following conclusions were drawn to the locations of the center of resistance according to the number of teeth, the change of distal traction force for pure intrusion and the correlation to the change of vertical, horizontal location of the center of resistance according to alveolar bone loss. 1. When the axial inclination and alveolar bone height were normal, the anteroposterior locations of center of resistance of upper anterior teeth according to the number of teeth contained were as follows : 1) In 2 anterior teeth group, the center of located in the mesial 1/3 area of lateral incisor bracket. 2) In 4 anterior teeth group. the center of resistance was located in the distal 2/3 of the distance between the bracket of lateral incisor and canine. 3) In 6 anterior teeth group, the center of resistance was located in the central area of first premolar bracket .4) As the number of teeth contained in anterior teeth group increased, the center of resistance shifted to the distal side. 2. When the alveolar bone height was normal, the anteroposterior position of the point of application of the intrusive force was the same position or a bit forward position of the center of resistance at application of distal traction force for pure intrusion. 3. When intrusion force and the point of application of the intrusive force were fixed, the changes of distal traction force for pure intrusion according to alveolar bon loss were as follows :1) Regardless of the alveolar bone loss, the distal traction force of 2, 4 anterior teeth groups were lower than that of 6 anterior teeth group. 2) As the alveolar bone loss increased, the distal traction forces of each teeth group were increased. 4. The correlations of the vertical, horizontal locations of the center of resistance according to maxillary anterior teeth groups and the alveolar bone height were as follows : 1) In 2 anterior teeth group, the horizontal position displacement to the vortical position displacement of the center of resistance according to the alveolar bone loss was the largest. As the number of teeth increased, the horizontal position displacement to the vertical position displacement of the center of resistance according to the alveolar bone loss showed a tendency to decrease. 2) As the alveolar bone loss increased, the horizontal position displacement to the vertical position displacement of the center of resistance regardless of the number of teeth was increased.

• Journal of Korean society of Dental Hygiene
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• v.14 no.3
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• pp.399-406
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• 2014

Objectives : The purpose of the study is to investigate the oral health behaviors between students studying in Vancouver, Canada and college students in Daejeon, Korea. Methods : A self-reported questionnaire was filled out by 239 students in November, 2013. The questionnaire consisted of oral health behavior including tooth brushing methods between two countries. Chi-square test and t-test were analyzed. The analyses were conducted using R version 2.14.2(R Foundation for statistical Computing, Vienna, Austria). Results : The number of tooth brushing in Korean students was higher than those in Canada. Fifty nine percent of the Koreans brushed their teeth 3 times a day while 62.3% of students in Canada brushed their teeth 2 times a day(p<0.0001). Those who were taught on oral health education tended to brush the teeth more frequently that those who had not. Koreans and Japanese tended to brush teeth more frequently after breakfast than the Taiwanese(p=0.005). Koreans also brushed teeth after dinner more frequently than Japanese, Taiwanese, and other foreigners(p=0.012). Conclusions : This study indicated that Koreans have better oral health behaviors in comparison to students studying abroad.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.3
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• pp.97-103
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• 1999

This paper investigates reduction of acoustic noise and cogging torque in a BLDC motor with larger stator slot open width. Using energy method, cogging torque is analytically determined with airgap MMF function and airgap permeance function and confirmed by FEM analysis. It shows that the cogging torque is firstly governed by NL GNL BNL with the fundamental period of NL, where NL is the least common multiple of the number of slots and the number of poles, GNL, airgap permeance function and BNL, airgap MMF function. It also shows that there exist several tooth width which minimizes the cogging torque, for the motors that smaller slot open width or stator teeth notching is not available. And it proposes a teeth pairing with two different tooth width which can effectively eliminate the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1dB.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.323-331
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• 1995

This study was undertaken to investigate the changes of tooth contacts following orthodontic treatment , using T-Scan system. Occlusal contacts in maximum intercuspation were examined in 26 patients at the end of the active phase of orthodontic treatment and again 3 months into the retention phase to abbess the initial posttreatment occlusal changes. The obtained results of this study were as follows : 1. The mean total number of contacts increased from 11.27 at the end of orthodontic treatment to 13.15 at the fellow up visit, which was found to be statistically significant (P<0.05). 2. The change of number of contacts on anterior teeth was unchanged. 3. The change of number of contacts on posterior teeth was found to be statistically significnat (P<0.01). 4. The change of fetal number of teeth in contact was significant (P<0.05). 5. The number of ant. teeth in contact was slightly increased. but Which was not found to be statistically significant (P>0.05). 6. The number of post. teeth in contact significantly increased, which was statistically significant (P<0.05). 7. A statistically significant relationship was found between the total number of contacts at the end of treatment and the change in the contacts over time. The fewer the number of tooth contact was at the end of orthodontic treatment, the greater number of tooth contact increased over time(r=-0.38, P<0.05).

• The Journal of the Korean dental association
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• v.57 no.10
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• pp.588-594
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• 2019

The fusion is an anomalous union of two or more tooth germ at some stage in the development process resulting in a decreased number of teeth in the dental arch. Fusion is common odontogenic anomaly but triplication of primary teeth is a rare phenomenon. We report a case of a 3 - year - old girl who visited our clinic for the pain on maxillary anterior tooth. The patient was diagnosed by the fusion of a the maxillary primary right central and lateral incisor with a supernumerary tooth and caries of dentine. And then, Endodontic treatment and composite resin restoration were performed on the triple teeth. After follow-up of 6 months period, there was no marked complications.

• Journal of Korean Academy of Oral Health
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• v.42 no.4
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• pp.145-151
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• 2018

Objectives: The purpose of this study was to interpret regional disparities in the number of teeth sealed with pit and fissure sealants, identify the factors that affect these disparities and find solutions for the same. Methods: Data were collected from the National Health Insurance Service and Korean statistical information service using metropolis-city-rural area dental health infrastructure variables, regional health behavior variables, and local finance-related variables. Results: In 2015, the number of teeth sealed with pit and fissure sealants per 100 people was higher in the metropolis or city than in the rural area. There was a positive correlation between the number of teeth sealed with pit and fissure sealants and the number of dentists, dental hygienists, dental institutions, standardization rate of subjective awareness of well-being, standardization rate of brushing after lunch, and the proportion of welfare budget in the general budget. There was a negative correlation with the annual standardization rate of health institution use, the standardization rate of unused medical services, and the local government's financial independence. According to the final model of the multiple regression analysis, while the impact of infrastructure on dentistry was not statistically significant, the statistical significance of standardization rate of brushing after lunch, the local government's financial independence, and the proportion of welfare budget in the general budget were maintained. Conclusions: To reduce regional disparities in the volume of use of pit and fissure sealants, it was concluded that it may be effective to select regions with a consideration of the level of regional economic power, implement separate and appropriate policies and projects, and improve the awareness in residents.

• Journal of Korean Dental Hygiene Science
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• v.7 no.1
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• pp.1-15
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• 2024

Background: This study aims to determine the association between the number of remaining teeth and oral health-related quality of life according to economic activity status in elderly. Methods: Data from the 9th Korean Longitudinal Study of Ageing (KLoSA) were used to analyze 6,004 older adults aged 59 years and older. The number of remaining teeth was categorized as less than 20 and more than 20, and the Geriatric Oral Health Assessment Index (GOHAI) was used to measured the oral health-related quality of life of the elderly. Independent t-tests were performed to compare demographic, economic, sociodemographic, and health characteristics, as well as GOHAI scores, between economically active and inactive individuals. In the case of ANOVA analysis, Scheffe's post hoc analysis was performed to confirm statistical significance between groups. Linear regression analysis was conducted to determine the influence of the number of remaining teeth on GOHAI according to economic activity status. Results: Among the study population, 33.9% were economically active, which is approximately half the proportion of those were not economically active. The mean GOHAI scores were 43.32 and 40.15 for economically active and economically inactive individuals with 20 or more residual teeth, respectively (p<0.001). Simple linear regression analysis revealed that having more than 20 remaining teeth was associated with a statistically significant increase in GOHAI by approximately 4.56 times and 4.92 times compared to having fewer than 20 teeth for economically active and non-economically active individuals, respectively (p<0.001). Multiple linear regression analysis, adjusted for demographic, economic, sociodemographic, and health characteristics, showed that having more than 20 remaining teeth was associated with a statistically significant increase in GOHAI by approximately 3.62 and 2.97 times compared to having fewer than 20 teeth in economically active and non-economically active individuals, respectively (p<0.001). Conclusion: This study explored economic activity status as one of several approaches to enhance the oral health-related quality of life of the elderly. By using the number of remaining teeth as an indicator of oral health status. supporting economic activity could potentially improve both oral health and overall quality of life for older individuals. Such interventions may have positive effects on policy outcomes, including reducing economic inequality by promoting economic engagement among the elderly.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.75-80
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• 2019

PURPOSE. The purpose of this study is to investigate the effects of aging and various risk factors on the oral environment and to analyze them in 3-dimensions. MATERIALS AND METHODS. A total of 800 patients were enrolled in this study, and subjects were divided into 4 groups by age-under 55, 56 - 65, 66 - 75, and over 76. Based on their most recent visit, the number of crowns, bridges, implants, and the remaining natural teeth were recorded. Smoking habits, along with presence of diabetes and hypertension, were surveyed, as risk factors were also set as a variable. Comparisons among the groups or within the groups were performed by independent t-test, and one-way and two-way ANOVA. Kruskal-Wallis test and Mann-Whitney U test were used for analysis. It was assumed to be statistically significant when P value is below .05. RESULTS. Changes in the number of crowns, bridges, implants, and the remaining natural teeth by age were statistically significant. When we examined the effect of risk factors on the change of variables with age, hypertension was found to affect the number of bridges. Diabetes and smoking were found to affect the number of the remaining natural teeth. The other variables were not statistically significant. CONCLUSION. Aging is considered to be an important variable affecting the change of oral environment. Among the risk factors, the presence of smoking habit and diabetes is thought to have a great influence on the change of the number of the remaining natural teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.4
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• pp.274-282
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• 2013

The goal of this study was to analyze prevalence and distribution of congenitally missing teeth in 3302 patients from 7 to 15 years old, who had visited and taken panoramic radiographs at the Department of Pediatric Dentistry, from January 2008 to December 2012. The prevalence of hypodontia in the males (5.9%) was slightly higher than in the females (4.7%). In the affected patients, the mean number of congenitally missing teeth in the mandible was statistically higher than in the maxilla (p < 0.05). However, there was no significant difference in the number of congenitally missing teeth between left and right dentitions (p > 0.05). Excluding the Mn. third molars, the most frequent congenitally missing teeth site was the Mn. second premolars. In contrast, the most infrequent congenitally missing teeth sites were the Mx. and Mn. first premolars, and Mx. central incisors. The bilateral combination or antagonistic quadrants combination of congenitally missing teeth in hypodontia patients was 80.3%. The result of this study will contribute to clinicians to make accurate diagnosis and establish favorable treatment plans, by offering invaluable data about the number and distribution of congenitally missing teeth.