• Journal of Oral Medicine and Pain
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• v.21 no.1
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• pp.89-101
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• 1996

This study was performed to investigate influence of the changes of head posture on resting electromyographic (EMG) activity in anterior temporalis, masseter, sternocleidomastoid muscle and trapezius, and on status of occlusal contacts. For this study twenty-nine patients with temporomandibular disorders(TMD) and thirty dental students without any masticatory symptoms were selected as patients group and control group, respectively. EMG activity($\mu$V) at rest was observed in four kind of head postures such as natural or normal head posture(NHP), forward head posture(FHP), upward head posture(UHP), downward head posture(DHP), and in NHP and FHP, EMG activity with flat occlusal splint was also checked. BioEMG$^\textregistered$(Bioelectromyograph, Bioresearch Inc., USA) was used to record EMG activity in the above four muscles with eight locations on both sides. The author used T-Scan$^\textregistered$(Tekscan Co., USA) system to investigate the changes of oclusal contats on clenching in the four head postures about number, force, time(duration) and total left-right statistis(TLR, occlusal stability crossing left-right dental arch on clenching). For taking in upward or downward head posture, head was inclined $10^{\circ}$ upward or downward and CROM$^\textregistered$ (cervical-range-of motion, Performance attainment Inc., USA) was used to maintain same posture during the procedure. The results obtained were as follows : 1. For resting EMG activity, anterior temporalis did not show any difference by change of head posture, but masseter and sternocleidomastoid muscle showed higher value of EMG activity in FHP and UHP, and trapezius showed higher value of EMG activity in FHP and DHP. 2. EMG activity of trapezius was higher than that of any other muscles in NHP, FHP, and DHP, but in UHP, the activity was the lowest reversely. 3. Patients group showed higher EMG activity than control group did in all the muscles in NHP. And significant difference between the two groups were also observed in anterior temporalis in FHP, in sternocleidomastoid muscle in UHP, and in sterno-cleidomastoid muscle and trapezius in DHP with higher activity in patients group. 4. There was no change of EMG activity in NHp with splint, but EMG activity in anterior temporalis and masseter was decreased in FHP with splint. 5. In general, status of occlusal contacts was not changed with head posture in all subjects, and difference between patients group and control group was only noted for number and force of tooth contact in UHP and DHP with more value in control group. 6. Correlationship between EMG activity and number ad force of tooth contacts was shown negatively with regard to masseter in NHP, and trapezius in UHP and DHP.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.19-28
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• 2022

In removable partial dentures, abutment teeth are essential for support, maintenance, and stability of partial dentures, and are an important factor in the fabrication of functional dentures. If the number of periodontally sound abutments is sufficient and they are located on both sides, it will be easy to manufacture functional dentures with good support, maintenance, and stability. But on the contrary, if the number of teeth is insufficient or if they are located on one side, it is biomechanically disadvantageous and relatively difficult to make functional denture. On the other hand, recently, implant-supported removable dentures, which reinforce the three elements of maintenance, support, and stability by using implant surveyed crown, have been frequently selected as treatment plans. In particular, by adding an implant surveyed crown when only a small number of residual teeth remain, mastication efficiency, esthetics, patient comfort, and pronunciation can be improved. In this case, bilateral posterior extension partial denture was fabricated using implant surveyed crown as abutments by placing implants in the premolars area opposite to the residual tooth unilaterally in the mandible. As a result, the asymmetry of the abutment was resolved, and the maintenance and stability of the denture was achieved.

• Applied Microscopy
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• v.40 no.1
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• pp.37-45
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• 2010

Captured wild specimens of the big white-toothed shrew, Crocidura lasiura were classified into three age classes by tooth wear and height of molars, and seasonal variations of breeding and reproductive organs were examined. Juveniles had not tooth wear in molars and height of the third molars were lower than the first and second molars, and had only non-breeding condition. Young adults had little tooth wear and the third molars reached to the first and second molars, and old adults had heavy tooth wear in molars, young adults and old adults had breeding or non-breeding condition according to the season. On the basis of histological examination, seasonal variations of breeding were confirmed that breeding condition of young and old adult males were continued from early February to early October although the breeding activity was the highest in April, that of females were continued from the end of March to October, males reached sexual maturity earlier than females. Whereas the breeding condition seems to cease for non-breeding season because of the deficiency of food resources, soil invertebrates. Young and old adult males of the breeding season had large testes with enlarged seminiferous tubules that were filled with numerous germ cells, and expanded caudal epididymides with a vast number of spermatozoa, and were more than 10.0 g in the body weight and 0.03 g in the testis and epididymis weight. The females of the breeding season were pregnant condition with 4~6 litters or had the Graafian follicles and the corpus lutea in the ovary, and were more than 9.6 g in the body weight.

• The Journal of Korean Society for School & Community Health Education
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• v.10 no.1
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• pp.87-104
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• 2009

Objective: In this study, the dental health care knowledge, dental health behaviors and dental health status of elementary school students were compared and analyzed in the cases of their schools having dental health care center or not one. Methods: The target groups were 167 students of A school (experimental group) where pit-and-fissure sealants, fluoride mouthrinsing, and fluoride gel application were carried out with all grades of students by school dental health care center and 158 students of B school (control group) where fluoride mouthrinsing, for all grades students and pit-and-fissure sealants for the first grade students are carried out but have no the school dental health care center. Results: This study was carried out through the answer sheets and recordings of dental inspection. The findings of this study are as follows: 1. The dental health care knowledge was compared and the results showed that on average 14.2$\pm$2.1 in experimental group and 14.0$\pm$1.9 in the control group were no significantly different (p>0.05). 2. The dental health behaviors were compared and the results showed that the experimental group was significantly different(p<0.05) in terms of the number of times of dental brushing a day, the method of tooth brushing, the time of tooth brushing, the experience of tooth brushing with fluorine, the kinds of snacks and tooth brushing in school after lunch. But there was no significant difference(p>0.05) in the time of tooth brushing and the tooth brushing after eating snacks. 3. The DMF rate was compared and the results showed the significantly difference between the average experimental group and 53.8$\pm$5.0 in the control group(p<0.05). 4. The DMFT index was compared and the results showed the significantly difference between the average 0.6$\pm$2 in the experimental group and 1.4$\pm$1.6 in the control group(p<0.05). 5. The DMFI rate was compared and the results showed the significantly difference between the average 4.2$\pm$8.3 in the experimental group and 9.5$\pm$11.0 in the control group. (p<0.05). 6. The DT rate were compared and the results showed the significantly difference between the average 10.2$\pm$29.5 in the experimental group and 32.4$\pm$44.0 in the control group(p<0.05). 7. The FT rate were compared and the results showed the significantly difference between the average 88.5$\pm$31.0 in the experimental group and 67.5$\pm$44.0 in the control group(p<0.05). Conclusions: Based on the results, above there was no significant difference in dental health care knowledge between both the experimental and the control group. But we discovered that the experimental group is better than the other one in dental health care behaviors and dental health status. Therefore, we could conclude that the school dental health care center efficiently carried out the dental care and treatment. As school dental health care centers did not work out efficiently in terms of their educating on the dental health acre knowledge, the related programs to be developed and supported.

• Applied Microscopy
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• v.40 no.3
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• pp.125-132
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• 2010

Captured specimens of the lesser white-toothed shrew, Crocidura suaveolens were classified into three age classes by tooth wear and seasonal variations of reproductive organs were investigated. Molars of juveniles had not tooth wear and the height of the third molars were lower than the first and second molars, young adults had smooth tooth wear and the third molars reached to the first and second molars, and old adults had heavy tooth wear and the third molars also reached to the first and second molars. On the basis of histological examination, seasonal variation of breeding was confirmed that breeding season of adult males was from early February to early October, having a peak of the breeding in April and July, and non-breeding season was from in the middle of October to late January. Young and old adult males of the breeding season had large testes with enlarged seminiferous tubules filling with numerous germ cells and expanded caudal epididymides with a vast number of spermatozoa, Young and old adult males of the non-breeding season had the small testes with the extremely slender seminiferous tubules filling with only spermatogonia and the reduced caudal epididymides without spermatozoa. Males weighing more than 3.9 g in the body weight and 0.013 g in the testis and epididymis weight reached sexual maturation in breeding season, and the females weighing more than 3.8 g in body weight of the breeding season were pregnant condition having 5~6 litters or had the Graafian follicles and the corpus lutea in the ovary.

• Journal of Korean society of Dental Hygiene
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• v.11 no.2
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• pp.197-211
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• 2011

Objectives : OHIP-14 and EQ-5D were used, targeting the residents of farming communities to identify the elements that influence oral cavity's health and quality of life due to health and to identify the importance of oral cavity's health in order to increase health of adults' oral cavity and quality of life via improved health. Methods : This research was conducted from July 17th, 2010 to August 16th, 2010 targeting 600 residents in Goryeong-gun, Gyeongsangbuk-do, aging over 40. The data has been analyzed using Mann-Whitney U test, Kruskal-Wallis test and hierarchical multiple regression through SPSS Win Program 18.0 version. Results : 1. OHIP-14 and EQ-5D based on general characteristics showed lower oral health-related quality of life and health-related quality of life on the following cases: women (p=0.004, p<0.001), older (p<0.001, p<0.001), lower scholastic ability (p<0.001, p<0.001), lower average of average spending money (p<0.001, p<0.001), higher number of chronic disease (p<0.001, p<0.001), less drinking (p=0.012, p=0.008), lower perceived oral health and health status (p<0.001, p<0.001) and non smoking showed only EQ-5D (p<0.001). 2. OHIP-14 and EQ-5D based on oral health behavior showed lower oral health-related quality of life and health-related quality of life on the following cases: no periodic oral check-up (p<0.001, p<0.001), less experience of oral health education (p<0.001, p<0.001), horizontal tooth-brushing method(p<0.001, p<0.001) and lower frequency of tooth-brushing showed only OHIP-14 (p=0.042). OHIP-14 and EQ-5D based on oral health status and subjective oral symptom showed lower oral health-related quality of life and health-related quality of life on following cases: number of existing tooth less than 20 (p<0.001, p<0.001), the number of missing teeth more than 9 (p<0.001, p=0.044), DMFT (Decay, Missing, Filling Teeth) index more than 18 (p<0.001, p<0.001), wears denture (p<0.001, p<0.001), edentulous (p<0.001, p=0.002), have xerostomia (p<0.001, p<0.001) and have chewing discomfort (p<0.001, p<0.001). 3. Factors affecting OHIP-14 were gender, age, perceived oral health status, perceived health status, number of existing teeth, dental status, xerostomia and chewing discomfort, and the of reliability (how well it explains) the final model was 48.7%. EQ-5D showed relevance on gender, age, presence of chronic disease, perceived health status, xerostomia, chewing discomfort and oral health-related quality of life, and the reliability of the final model was 42.9%. Conclusions : In order to improve the quality of life of ruralists, oral health needs to be improved or remained by increasing the rate of possession of the existing teeth and preventing the loss of teeth. In order to do so, improvement of accessibility of dental clinic, change of direction from treatment-centered to prevention-centered health care system, development of oral health education program and various oral health care policies which would vitalize continuous oral health care system are considered to be necessary.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.42 no.4
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• pp.182-186
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• 2016

Objectives: The purpose of this study was to analyze the incidence of indications for the removal of mini-plates over a five-year period in maxillofacial trauma patients. Materials and Methods: The medical records of 530 patients who underwent treatment with mini-plate fixation after maxillofacial trauma were reviewed for a five-year period (May 2007 to May 2012). Patients were evaluated concerning the number of mini-plates removed, age and gender distributions, time between insertion and removal, indication for removal, and site of removal. Results: The plates of 120 patients were removed (26 females and 94 males). The removal rate was 22.6%. The most frequent indication for removal was patient demand (81.7%), followed by tooth extraction (7.5%), and pain (3.3%). The most frequent removal site was the mandible (95.0%). Conclusion: The number of mini-plates removed was small, and the most common indication for removal was patient demand. There is no evidence to support a recommendation for the routine removal of titanium mini-plates.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.319-326
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• 1993

The purpose of this study was to evaluate the frequency of congenital missing teeth and supernumerary teeth in cleft patients. The subjects were divided into bilateral cleft lip and palate(BCLP), unilateral cleft lip and palate(UCLP) and cleft palate alone(CP alone) groups. 97 cleft patients(BCLP 15, UCLP 70, CP alone 12) between 6-20 years old were evaluated. Panorama film, Orthodontic chart and initial intraoral photogram were employed for this research. The obtained results were as follows. 1. The incidence of congenital missing teeth in total cleft samples was $57.7\%$, and the incidence of supernumerary teeth was $26.8\%$. Each incidence was higher than non-cleft. 2. The incidence of congenital missing teeth was the highest in BCLP and the lowest in CP alone. 3. The number of congenital missing teeth per perso was usually one, and the frequency was higher in the maxillary lateral incisors$(67.8\%)$, and maxillary second premolar$(14.9\%)$ than other teeth. 4. Most of tooth number anomalies in cleft patients were found in maxilla, especially adjacent region to the cleft site.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.2
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• pp.179-186
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• 2007

The decrease of masticatory function caused by tooth loss leads to a decrease of cerebral blood flow volume resulting in impairment of cognitive function and learning memory disorder. However, the reduced mastication-mediated morphological alteration in the central nervous system (CNS) responsible for senile deficit of cognition, learning and memory has not been well documented. In this study, the effect of the loss of the molar teeth (molarless condition) on the hippocampal expression of glial fibrillary acidic protein (GFAP) protein was studied by immunohistochemical techniques. The results were as follows : 1. The molarless mice showed a lower density of pyramidal cells in the cornu ammonis 1 (CA1) and dentate gyrus (DG) region of the hippocampus than control mice. 2. Immunohistochemical analysis showed that the molarless condition enhanced the time-dependent increase in the cell density and hypertrophy of GFAP immunoreactivity in the CA1 region of the hippocampus. The molarless condition enhanced an time-dependent decrease in the number of neurons in the hippocampal formation and the time-dependent increase in the number and hypertrophy of GFAP-labeled cells in the same region. The data suggest a possible link between reduced mastication and histological changes in hippocampal formation that may be one risk factor for senile impairment of cognitive function and spatial learning memory.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1949-1957
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• 2003

A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of a planetary gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The minimum rim thickness limit should be determined considering not only the critical stress but also the load sharing. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.