• 대한치과기공학회지
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• 제18권1호
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• pp.95-115
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• 1996

The esthetic factor for the esthetic prosthesis were studied on 300 persons. The praaticipants were 150 students registered under the Deparment of Dental Laboratoy Technology, Jisan Junior College at the present day of June, 1995 and their mothers. The results were as follows; 1. The number of persons with 28 teeth in their oralcatity was highest(P<0.01). They complained that they have only 28 teeth bacaues of the loss(deficiency) fo teeth due to their impacted teeth and dental caries. 2. The presons with feelings of dissatisfaction were large in number(P<0.01). They were dissatisfied with an abnormal tooth form(33.5%), tooth position(31.7%), tooth color(31.1%), and tooth size(3.7%) in order(P<0.01). 3. In their facial form, the most numerous were men with square form and women with ovoid form(P<0.01). Among the whloe number fo facial forms it appeared to decresae in the order of ovoied(41.8%), square(32.7%), square+tapered(20.5%), and tapered form(5%)(P<0.01). In a profile form, the most numerous were men with A form and women with B. Among the whole participants the most numerous were persons with B form and persons with A and C form were next in oder of numbers(P<0.01). 4. In discoloration of teeth, the most numerous were persons who have no discoloration. 5. In the esthetic recovery of anterior prosthesis the color matching of proximal teeth was not correct, but the outline of proximal teeth was to be reproduced correctly. 6. In the diastema of teeth, the number of persons who have no diastema was higher than that of persons who have a disatema(P<0.01) Among the persons who have diastema the most numerous were persons who have a diastema, and next were 2, 4, 3 and 5 diastemas in order. 7. In a meeting point of the midline of the body and the tooth the number of person hanving a meeting point was higher than that of persons who did not fit each other(P<0.01). The bias direction of midline teeth appeared to be affected by chewing direction, prosthesis location, and posterior location. 8. The length and width of teeth in the tooth size were suitable(P<0.01). The number of persons who have central teeth longer than lateral teeth was high(P<0.0). 9. In the results of smile analysis, the line form connected with incisal edge of upper canine were parallel(P<0.01). When smile the location fo upper lips should be in accord with the central area of teeth(P<0.01) and lower lip should be atteched to the edge of anterior teeth in order to be esthetic. 10. Among the number of upper teeth we can see the most numerous were 8 teeth and next were 10, 6 and 12 in order.

• 대한소아치과학회지
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• 제32권3호
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• pp.409-415
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• 2005

영구 전치의 매복은 제 3 대구치나 견치에 비해서 드물게 나타나지만 학령기 아동에서 관찰할 수 있다. 매복치아의 원인은 외상, 공간 부족, 치아의 맹출 경로상에 위치하는 과잉치, 유치의 치근단 감염 등 다양하다. 매복된 치아는 부정교합과 인접치아의 치근 흡수, 낭종 등의 병적 변화를 유발할 수 있으므로 임상적 검사와 방사선학적 검사를 통해 정확한 위치를 확인하고, 적절한 치료계획을 통해 정상 맹출을 유도하여야 한다. 매복된 치아가 병적 변화를 일으킨 경우나 인접치에 손상을 주었을 경우에 발치를 시행하게 된다. 그러나 교정적 견인을 통해 기능과 심미성을 회복시켜 줄 수 있으므로 조기 발견과 발견시의 올바른 진단과 치료 계획을 수립하는 것이 중요하다. 교정적 견인시에는 매복치를 배열할 공간의 확보와 고정원에 대한 고려가 선행되어야 한다. 견인시 적절한 방향의 힘을 통해서 치근의 흡수 등의 부작용이 일어나지 않도록 해야 한다. 본 증례는 매복된 전치들을 forced eruption을 통해서 정상적인 맹출 방향으로 유도한 치험례이다.

• Restorative Dentistry and Endodontics
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• 제7권1호
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• pp.59-63
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• 1981

Ninety four human mandibular third 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 two canals, but 17.0% of the teeth were found to have one canal, 17.0% of them three canals, 3.2% of them four canals and l.1% of them five canals. 2. In so far as observing one canal per root, 17.0% of the teeth were found to have one canal in single-rooted tooth, 48.9% of them in mesial root and 58.5% of them in distal root. 3. In roots with two or three canals, the separated apical foramen appeared in 55.6% in single-rooted tooth, 64.3% in mesial side and 80.0% in distal side, and the common apical foramen appeared in 44.4% in single-rooted tooth, 35.7% in mesial side and 20.0% in distal side. 4. Of the two root canals in one root, 19.1% of the canals were found to have transverse anastomoses and were usually located in the apical third of the root. 5. 63.8% of 94 teeth were found to have lateral canals, and ramifications were mainly located in the apical third of the root.

• 대한치과교정학회지
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• 제23권3호
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• pp.375-389
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• 1993

The delivery of optimal orthodontic treatment is greatly influenced by a clinician's ability to predict and control tooth movement achieved by applying known force systems to the dentition. It is important to determine the location of the center of resistance of a tooth or group of teeth to better understand the nature of their displacement characteristics under the various force levels. The purpose of this study was to define the location of the centers of resistance of various units of the upper anterior segment for lingually directed 100gm and 200gm force in a dry human skull. The units investigated were composed of four incisors and six anterior teeth. In addition, the effect of change in force magnitude on the location of the center of resistance of these units was investigated. The laser reflection technique was used to measure the initial displacements of the consolidated teeth under loading. The results were as follows: 1. The instantaneous center of resistance for the four anterior teeth was located vertically between level 4 and level 5-that is, at $37.4\%$ apical to the cementoenamel junction level. 2. The instantaneous center of resistance for the six anterior teeth was located vertically just beneath level 5-that is, at $50.3\%$ apical to the cementoenamel junction level. 3. Increasing force levels had little effect on the location of the center of resistance of a given unit. 4. The location of the instantaneous center of resistance shifted apically as the number of dental units consolidated increased.

• 대한치과보철학회지
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• 제25권1호
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• pp.341-353
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• 1987

The purpose of this study was to investigate the gingival response to the location of the crown margin and the gingival response to the period of crown placement. Twenty one patients were selected for this study. The patients fitted into the research condition. The crown margins of anterior teeth were located at crest and supragingivally. The crown margins of posterior teeth were located at crest, subgingivally and supragingivally. Plaque index and gingival index were measured before tooth preparation and 1 week,4 weeks, 6 weeks after crown placement. The results were as follows: 1. There was no significance in the gingival response to the location of crown margin in short term period. 2. As the period of crown placement was extended, plaque index and gingival index were gradually increased. 3. Plaque index and gingival index of tooth surfaces were increased in the order of the interproximal surfaces, lingual surfaces and buccal or labial surfaces.

• Imaging Science in Dentistry
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• 제53권4호
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• pp.303-312
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• 2023

Purpose: This study investigated the prevalence of developmental and acquired pathologic conditions associated with impacted third molars (3Ms) in a Southern Brazilian population and evaluated whether demographic and tooth characteristics were correlated with the presence of bone or tooth lesions. Materials and Methods: Panoramic radiographs were assessed for developmental (bone-related) or acquired (tooth-related) pathoses associated with impacted upper or lower 3Ms. Data on tooth positioning, tooth development, and patient demographics were collected. A trained, calibrated postgraduate student evaluated all images. Binary and multivariate logistic regression models were used to assess associations between outcomes and the demographic and radiographic variables. The threshold for statistical significance was set at 5% (P<0.05). Results: The sample comprised panoramic radiographs from 2054 patients, predominantly female (59.2%), with a mean age of 27.2±11.5 years. Overall, 4066 impacted 3Ms were evaluated, revealing 471 (11.6%) developmental and 710 (17.5%) acquired pathoses. Among the developmental pathoses, 460 (95.2%) were indicative of dentigerous cysts. Male sex, lower 3M location, vertical or distoangular positioning, and incomplete root formation were associated with an elevated likelihood of developmental pathology. Lower tooth position, complete root formation, and partial eruption were linked to an increased probability of an acquired pathology in the third or second molar. Conclusion: The prevalence of pathologic conditions associated with impacted 3Ms was low. Male sex, lower 3M placement, horizontal or distoangular positioning, and incomplete root formation were associated with developmental pathoses, while lower tooth position, complete root formation, and partial eruption were related to acquired pathoses.

• 한국정밀공학회지
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• 제14권2호
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• pp.102-112
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• 1997

This paper describes the method that can construct kinematically admissible velocity fields for forging of gear-like components which have tooth shape around the cylinder. The kinematically admissible velo- city fields for the various gear-like components, involute spur gear, trapezoidal spline, square spline, ser- ration and trochoidal gear, were constructed by pilling up the velocity components according to the shape of tooth and billet. The billets, of hollow and solid, were Al 2218 and 2024. To verify the method, the analyses and experiments were carried out and compared with each other. For analyses, the half pitches of com- ponents were divided into several deformation regions based on their tooth profile. A neutral surface was used to represent the inner flow of material during forging. Its location varied with the energy optimazation and its contour varied with the number of teeth. In experiment, the contour of material filling up the tooth zone is hyperbolic curve caused by the frictional drag on the interface of die-wall/workpiece but, in the analysis, it is an arc which retains the same contour during all forging operation.

• Journal of Periodontal and Implant Science
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• 제44권2호
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• pp.50-56
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• 2014

Purpose: The aims of this study were to measure the distance of the intraosseous vascular anastomosis in the anterolateral wall of the maxillary sinus from different reference points, and to correlate the location of the intraosseous vascular anastomosis with the tooth position and the residual bone height of the maxilla. Methods: Computed tomography (CT) images were taken from 283 patients undergoing dental implants placement in the posterior maxilla. Three horizontal lines were drawn at the ridge crest, maxillary sinus floor, and the position of the anastomosis. A vertical second line at the center of each tooth was drawn perpendicular to the horizontal lines. The distance from the ridge crest to the maxillary sinus floor and the distance from the maxillary sinus floor to the bony canal were measured from the intersections of the horizontal and vertical lines. The residual alveolar bone height was used to categorize three groups: group 1,<4 mm; group 2, between 4 and 8 mm; and group 3, >8 mm. Results: The residual bone height values of different tooth positions were significantly different (P=0.0002). The distance from the maxillary sinus floor to the intraosseous vascular anastomosis was significantly different between groups 1 and 3 (P=0.0039). At the molar sites, a moderate negative correlation was found between the residual bone height and the distance from the maxillary sinus floor to the intraosseous anastomosis. The distances of the alveolar ridge crest and the maxillary sinus from the intraosseous vascular anastomosis were not significantly different between sexes. Conclusions: Within the limitations of this study, sites with a higher residual bone height in the molar regions were at a relatively high risk of artery damage during window osteotomy preparation; therefore, we recommend taking more precautions when using a lateral approach for sinus elevation.

• 대한치과교정학회지
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• 제31권1호
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• pp.15-24
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• 2001

원하는 형태의 치아이동을 얻기 위해서는 M/F(Moment/Force) ratio의 조절이 필요하며, 이출 위해서는 치아의 저항중심의 위치를 아는 것은 매우 중요한 일이다. 본 연구에서는 실제 치아주위 환경을 비교적 유사하게 재현할 수 있는 치조골상과 치아의 이동을 시뮬레이션하는 장치를 제작하고, LVDT출 이용한 3차원 운동을 실시간으로 측정할 수 있는 시스템을 사용하여, 힘에 대한 3차원 공간상에서의 치주인대 응력 분포 양상 및 치아 저항중심과 회전축의 위치변화를 계측한 결과 다음과 같은 결론을 얻었다. 1. 상악 견치에 원심방향으로 힘을 가했을 때, 치아의 저항중심의 위치는 힘의 크기와는 무관하였으며, 치근의 치경부측 약 $29\%$ 부위에 위치하였다. 이는 2차원 모형($42\%$) 보다 치관 쪽에 위치한다. 2. 모멘트만 가하는 경우 치아의 저항중심과 회전축은 일치하였다. 3. 치아에 가해지는 모멘트가 증가하는 경우 방향에 관계없이 치아는 정출되는 경향을 보였다. 4. 힘이 가해진 위치, 저항중심, 회전축간에는 일정한 관계가 성립했다 (a x b = $49.6\;mm^2$). 이 관계식을 통해서 수평력이 가해질 때 예상되는 치아운동 양상을 알 수 있다. 5. 수평력이 가해질 때 회전축의 위치는 일직선으로 나타난다.

• 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.