• 대한소아치과학회지
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• 제37권1호
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• pp.117-123
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• 2010

치아 맹출이란 치아가 치조골 내의 발생 장소에서부터 교합면쪽으로 이동하여 구강 내로 출현한 후 치아의 기능적 위치까지 이동하는 것을 말한다. 유치의 치근부에서 발육하는 영구치배는 천천히 유치의 치근과 지지하는 치조골 부위를 흡수하면서 맹출하고, 이와 동시에 영구 치배의 치근과 치조골 및 기저골을 성장시킴으로써 영구치의 지지부위가 확립된다. 대개 영구전치의 치배는 유전치의 치근단 설측에 위치하는데 잘 발달된 도대삭(gubernacular cord)을 따라서 교합면상으로 맹출하게 된다. 이소 맹출이란 일반적으로 치배가 본래 발생 위치에서부터 예상되는 정상 맹출경로에 이상이 있는 것을 말한다. 즉, 치아가 치조골 내 발생 위치에서 예측되는 정상맹출 경로를 벗어나 맹출하는 것이다. 그 중 하악 측절치의 이소 맹출의 경우 치아의 위치를 바로잡는데 있어서, 그 치료 시기가 중요한 요소로 여겨지는데 일반적으로 혼합치열기 초기가 바람직한 치료시기이다. 하악전치가 이소 맹출한 경우 적절한 시기에 치료를 시행함으로써 공간 소실의 문제나 하악 전치부의 설측경사 등의 문제가 발생하는 것을 예방할 수 있다. 본 증례는 만 8세 여아에서 혀 아래쪽의 구강저 부근에 수평방향으로 이소 맹출하는 하악 우측 측절치를 주소로 연세대학교 치과대학병원 소아치과에 내원하였다. 컴퓨터 단층촬영(CT)을 이용하여 문제 치아의 치근 만곡 정도를 확인한 후, 혼합 치열기 초기에 lip bumper와 buccal arch를 이용하여 26주간 적극적인 견인적 처치를 시행하였다. 결과적으로 이소 맹출한 측절치를 본래 위치로 이동시켰으며 나머지 영구치의 맹출에 대한 관찰 및 평가 후 전반적인 교정치료를 진행하기로 계획하였다.

• Journal of Korean Dental Science
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• 제3권1호
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• pp.17-24
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• 2010

Objective : To investigate the prevalence of dental anomalies and to determine the associations between dental anomalies in permanent teeth Materials and methods : The samples were 1,240 patients (760 females and 480 males, mean age=15.1 years) who visited the Samsung Medical Center. Dental anomalies were diagnosed using pre-treatment dental casts, radiographs, clinical examinations, and medical/dental histories. Prevalence and association were investigated according to gender and sidedness. The Chi-square test was performed for statistical analysis. Results : The most common missing tooth was the lower lateral incisor, followed by the lower and upper second premolars. This particular dental anomaly is characteristic of the East Asian population (prevalence of congenital missing tooth=12.3%). The upper anterior area was the most frequently affected area (prevalence of supernumerary tooth was 1.5%). The presence of a supernumerary tooth was more prevalent in males than in females (p<.05, odds ratio=3.2). The most frequently affected tooth was the upper canine (prevalence of impacted tooth=4.3%). Unilateral impaction of the upper canine occurred significantly more often compared to bilateral impaction (p<.001). The prevalence of peg lateralis was 2.7%. The presence of congenital missing tooth was closely associated with peg lateralis (p<.01). If children aged 7~8 years have peg lateralis, the rest of the teeth should be checked for congenital absences. Conclusion : The early detection of dental anomalies and understanding of their associations help clinicians determine the appropriate treatment timing and methods of dealing with these anomalies.

• Journal of Oral Medicine and Pain
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• 제13권1호
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• pp.13-21
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• 1988

The author studied the vertical height of tooth crown and the amounts of alveolar bone resorption with age. All 84 subjects(44 male, 40female) who visited Dental hospital of Wonkwang University with no history of sever periodontal disease and no experience of periodontal surgery. 84 subject were divided into 3 groups by age, that is, group I(28-32yrs), group II(38-42yrs), and group III(48-52yrs). Informal radiogram with bite wing film(horizontal angulation : $0^{\circ}$, vertical angulation : $+5^{\circ}~+10^{\circ}$) were taken on premolar and molar area. The distances from cusp tip to cementoenamel junction (vertical height of tooth crown) and from cementoenamel junction alveolar crest(amount of alveolar bone resorption) were measured, and then recorded data from 946 teeth were statistically analysed. This study was undertaken to obtain the data for age estimation by the changes of tooth crown height and alveolar bone resorption in the point of forensic odontology. The obtained results were as follows : 1. The average crown height of mandibular right 1st. molar was 7.1mm in group I, 6.7mm in group II, and 6.6mm group III, and the average amount of alveolar bone resorption on mandibular right 1st. molar were 1.8mm in group I, 2.5mm in group II, and 3.0mm in group III. Ratio of tooth crown height to amount of alveolar bone resorption was 4.0:1 in groupI, 2.7:1 in group II, and 2.2:1 in group III, the ratio was decreased with age. 2. In comparison with upper teeth and lower teeth in ipsilateral side, the average value of tooth crown height and amount of alveolar bone resorption were slightly higher in upper arch than those in lower arch, but there was not a statistically significant difference. 3. The ratio of height of tooth crown to amount of alveolar bone resorption was decreased with age, and which depended mainly upon the change of amount of alveolar bone resorption rather than the change of tooth crown height.

• The Journal of Advanced Prosthodontics
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• 제11권3호
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• pp.169-178
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• 2019

PURPOSE. While dental implants have displayed high success rates, poor mechanical fixation is a common complication, and their biomechanical response to occlusal loading remains poorly understood. This study aimed to develop and validate a computational model of a natural first premolar and a dental implant with matching crown morphology, and quantify their mechanical response to loading at the occlusal surface. MATERIALS AND METHODS. A finite-element model of the stomatognathic system comprising the mandible, first premolar and periodontal ligament (PDL) was developed based on a natural human tooth, and a model of a dental implant of identical occlusal geometry was also created. Occlusal loading was simulated using point forces applied at seven landmarks on each crown. Model predictions were validated using strain gauge measurements acquired during loading of matched physical models of the tooth and implant assemblies. RESULTS. For the natural tooth, the maximum vonMises stress (6.4 MPa) and maximal principal strains at the mandible ($1.8m{\varepsilon}$, $-1.7m{\varepsilon}$) were lower than those observed at the prosthetic tooth (12.5 MPa, $3.2m{\varepsilon}$, and $-4.4m{\varepsilon}$, respectively). As occlusal load was applied more bucally relative to the tooth central axis, stress and strain magnitudes increased. CONCLUSION. Occlusal loading of the natural tooth results in lower stress-strain magnitudes in the underlying alveolar bone than those associated with a dental implant of matched occlusal anatomy. The PDL may function to mitigate axial and bending stress intensities resulting from off-centered occlusal loads. The findings may be useful in dental implant design, restoration material selection, and surgical planning.

• 대한소아치과학회지
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• 제37권2호
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• pp.151-158
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• 2010

연구목적은 모유 또는 분유 섭취 시 나타나는 유치열의 치면별 우식패턴에 차이가 없으며 수유기간에 따른 차이도 없다는 가설을 검증하는 것이었다. 익산시, 청주시, 울산광역시의 36-71개월 어린이 815명을 대상으로 구강검사로 치면별 우식경험도를 조사하고, 보호자들을 대상으로 설문지 조사법으로 모유와 분유 중에서 생후 1년간 주로 수유한 것과 수유 기간을 조사하였다. 모유군과 분유군 간 우식경험유치면수(dmf)의 차이는 유의하지 않았다. 모유군에서 분유군보다 우식경험도가 더 높았던 유치군은 상악 유전치이었고, 유치면군은 상악 유전치 협설면과 인접면이었으며, 유치는 상악 유절치와 상하악 제2유구치이었고, 유치면은 상악 유중절치의 협면과 원심면, 상악 유측절치의 협설면, 인접면, 상악 제2유구치의 설면, 인접면, 교합면, 하악 제2유구치의 협면, 원심면이었다. 모유군에서 수유기간이 증가함에 따라 우식경험유치면수가 증가한 유치군은 상악 유전치와 상악 유구치이었고, 유치면군은 상악 유전치의 인접면, 상악 유구치의 협설면, 인접면, 교합면, 하악 유구치의 인접면이었으며, 유치는 상악 유전치, 상악 유구치, 하악 제2유구치이었고, 유치면에서는 상악 유전치의 인접면, 상악 제1유구치의 협설면, 인접면, 교합면, 상악 제2유구치의 협면, 하악 제2유구치의 근심면이었다. 분유군에서는 수유기간 3년 이상에서 우식경험유치면수가 증가하였으나 차이가 유의하지 않았다. 수유와 관련되어 발생하는 상악 유절치의 중증 유아기 우식증은 분유를 수유하는 경우보다 모유를 수유하는 경우에 더 많이 발생하였다. 모유 수유를 2년 이상 하는 경우에는 상악 유절치의 우식 예방을 위한 조치가 필요하다.

• 대한치과교정학회지
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• 제24권3호
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• pp.721-733
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• 1994

Orthodontic tooth movement is closely related to the stress on the periodontal tissue. In this research the finite element method was used to observe the stress distribution and to find the best condition for effective tooth movement in the case of unilateral molar expansion. The author constructed the model of lower dental arch of average Korean adult and used $.032'\times.032'\times60mm$ TMA wire. The wire was deflected in the horizontal and vertical direction to give the 16 conditions. The following results were obtained ; 1. When the moment and force were controlled properly the movement of anchor tooth was minimized and the movement of moving tooth was maximized. 2. As the initial horizontal deflection increased the buccal displacement of both teeth was also increased. As the initial horizontal deflection increased the lingual movement of anchor tooth and the buccal movement of moving tooth increased. 3. When the initial horizontal and vertical deflection rate was 1.5 the effective movement of moving tooth was observed with minimal displacement of anchor tooth.

• 대한치과보철학회지
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• 제8권1호
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• pp.9-14
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• 1968

A total of 11,039 permanent missing teeth and their 2,696 prosthetic replaced teeth in 6,123 Korean patients were selected for this study, Analyzing the data according to age, sex, jaw and the location, following results were obtained. 1. Tooth mortality and replacement were higher in female than in male. 2. Replaced teeth were only 24 percent of missing teeth. 3. More teeth were extracted and replaced on lower jaw in young patients and on upper jaw in old patients. 4. There are no significant difference in right and left sides of both jaws in missing and replaced teeth, respectively. 5. First molar was the highest percentage in both mortality and replacement. 6. Upper tooth mortality and replacement were higher in anterior portion and lower in posterior portion.

• 보건교육건강증진학회지
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• 제13권2호
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• pp.167-183
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• 1996

Human teeth vary widely in color. Practitioner and patients are concerned with preventing and correcting discolored or dark teeth to achieve and maintain stain-free, white teeth. Tooth brushing cannot alter tooth color but it can remove adhering films and stains. The esthetics of natural dentition can be improved by bleaching and this process can be applied to intrinsically and extrinsically stained teeth. The need for a brighter, more attractive smile has made rapid growth in the market for tooth whiteners. There is no doubt these products work as whiteners, at least on mild to moderate stains, but the safety of these products are unclear. In this experiment, the effect of tooth whitener application on the color and microhardness of extracted human enamel was measured. RMS, RMT and NWT were used as tooth whiteners, and tooth paste(ETQ) and hydrogen peroxide solution(HPO) were used as controls. 35 caries-free extracted human molars were embedded and polished with the exposed enamel diameter of 4 mm. The tooth whiteners and control agents were applied according to the manufacturers' instructions or clinically simulated procedures for eight weeks, and measurements were repeated every two weeks. Value(L＊) difference was measured using Differential Colorimeter(Model TC-6FX, Denshoku Co., Japan), and microhardness was measured using microhardness tester(Mitsuzawa Seiki Co., Japan). The results were as follows; 1. After application of agents for eight weeks, the Vickers hardness increased significantly in the ETQ, RMS and RMT application group(p〈0.01), and that decreased significantly in NWT application group(p〈0.01), but in HPO application group there was no significant change. The change in microhardness was greatest in NWT application group(p〈0.01). 2. After application of tooth whiteners and controls for eight weeks, the value change of toothpaste application group was significantly lower than those of other agents groups(p〈0.01), and there was no significant difference in value(L＊) change among tooth whitener groups(p〉0.01). 3. The application of tooth paste and paste type tooth whitener made gradual value change, but hydrogen peroxide gel type tooth whitener and hydrogen peroxide solution made rapid value change during initial application period.

• 대한치과보철학회지
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• 제22권1호
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• pp.79-84
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• 1984

The stability of teeth is an important measure of the periodontal health. This study was designed to determine if there was a relation between the patterns of disclusion and a tooth mobility. An evaluation was made on 117 persons with Angle's class I occlusion who were free from histories of orthodontics, removable or fixed prosthesis, and anterior crowding or open contacts. The results were as follows: 1. In this study, 17.52% of the subjects were exhibited canine protected occlusion. 2. In protrusive movements, 75.21% of the subjects were exhibited incisor guided occlusion and the subjects of canine guided occlusion was the smallest. 3. The canine tooth of mouths having canine-protected occlusions had slightly lower mean tooth mobility scores than the canine of mouths having group function occlsion, but there was no significances. 4. The tooth mobility score of central incisor had higher than that of lateral incisor.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1720-1729
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• 2001

Wear characteristics of Nylon and acetal pinions against steel gears for different pitch line velocities was studied with a power circulating gear test rig under unlubricated condition. Specific wear rate was measured as a function of tooth number, module, tooth width and total revolution. The worn tooth surfaces were examined with a profile projector. The Nylon pinion showed lower specific wear rate than the acetal pinion. However, the Nylon pinion was fractured at high tooth loads, whereas the acetal pinion exhibited a steady wear behavior. The wear characteristics of Nylon pinion varied significantly with the Pitch line velocity. Wear occurred most severely at the tooth tip and the region immediately below the pitch line of pinion. The dominant wear mechanisms were adhesion and abrasion.