• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.326-331
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• 2000

In this study, residual stress was investigated experimentally to evaluate damaged layer in high-sped machining. In machining difficult-to-cut material, residual stress remaining in machined surface was mainly speared as compressive stress. The scale of this damaged layer depends upon cutting speed, feed per tooth and radial cutting depth. Damaged layer was measured by optical microscope. The micro-structure of damaged layer was a mixed maternsite and austenite. depth of damaged layer is increased with increasing of cutting temperature, cutting force and radial depth. On the other hand, that is slightly decreased with decreasing of cutting force. The increase of tool wear causes a shift of the maximum residual stress in machined surface layer.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.50.1-50.8
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• 2021

Although several techniques have been proposed to remove fiber-reinforced composite (FRC) post, no safe and efficient technique has been established. Recently, a guided endodontics technique has been introduced in cases of pulp canal obliteration. This study describes 2 cases of FRC post removal from maxillary anterior teeth using this guided endodontics technique with a dental operating microscope. Optically scanned data set from plaster cast model was superimposed with the data set of cone-beam computed tomography. By implant planning software, the path of a guide drill was selected. Based on them, a customized stent was fabricated and utilized to remove the FRC post. Employing guided endodontics, the FRC post was removed quickly and safely with minimizing the loss of the remaining tooth structure. The guided endodontics was a useful option for FRC post removal.

• 대한치과교정학회지
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• 제27권5호
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• pp.825-837
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• 1997

실험적 치아이동 후 보정기간 동안 고정방법이 치주인대 섬유의 재배열에 미치는 영향을 알아보기 위하여, 체중 20kg 내외의 성견에서 상악 제 3절치와 견치 사이에 견인 스프링을 이용하여 120 gm의 교정력을 3주간 가한 후 좌측에는 유연성 고정장치로 0.0215 인치 multistrand wire를, 우측에는 견고성 고정장치로 폴리 에틸렌 리본을 레진 접착제로 각각 장착한 다음 4주, 8주, 또는 12주 후 희생시켜 치주조직의 변화를 방사선 사진, 광학 현미경 관찰을 통하여 분석한 바 다음과 같은 결과를 얻었다. 1. 치아이동 후 압박측에서는 치주인대 공간의 압축과 함께 치주인대섬유가 굵어진 소견을 보였으며 인장측의 치주인대섬유는 신장되어 보였다. 2. 보정 4주 후 유연성 고정군에서는 치주인대섬유의 재배열이 관찰되었으나 견고성 고정군에서는 관찰되지 않았다. 3. 보정 8주 후부터는 두 군 모두에서 치주인대섬유의 재배열 소견이 관찰되었으며, 두 군간 치주인대섬유의 재배열 차이는 보이지 않았다. 4. 보정기간 동안 치주인대섬유의 재배열은 압박측 보다 인장측에서 빠른 소견을 보였다. 이상의 결과는 치아이동 후 견고하게 고정한 보정방법에서도 치주인대섬유의 재배열이 일어남을 보여주었고, 치아 보정시 폴리에틸렌 리본으로 고정한 보정장치도 유용하게 사용될 수 있음을 시사하였다.

• 대한소아치과학회지
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• 제36권2호
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• pp.305-309
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• 2009

치외치(Dens Evaginatus)란 교합면에 법랑질이 원추형으로 돌출되어 결절을 형성한 치아로 치아발육중 법랑기의 내측법랑상피가 외부로 과증식되거나 치수 간엽조직이 국소적으로 과증식되어 나타난다. 결절은 교합력이나 저작에 의해 파절 또는 마모되기 쉬우며 따라서 이로 인하여 치수노출에 의한 감염이 야기될 수 있다. 치외치는 예방목적으로 결절을 주기적으로 조금씩 갈아주어 2차 상아질을 유도하거나 전색제등으로 결절주위를 보강하여 자연마모를 유도할 수 있다. 반면 이미 증상을 보인 치아에 대해서는 근관치료를 시행하거나, 미완성치근인 경우 치근단유도술(Apexogenesis)이나 치근단형성술(Apexification)을 시행한다. 치근단유도술이란 생활력을 가진 미성숙 영구치의 손상, 또는 치아우식에 의한 치수노출 시 치수절단술을 시행하여 치수의 생활력을 유지시켜 정상적인 치근으로 발육하도록 유도하는 술식을 말한다. 주로 수산화칼슘을 이용한 통상의 치수절단술이 이용되고 이후 계속적인 치근형성 확인을 위해 주기적 방사선검사가 요구된다. 본 증례는 하악 좌측 제2소구치 부위의 동통을 주소로 내원한 한자에 대한 것으로, 임상검사결과 양측 소구치 부위에 치외치를 확인하게 되었다. 이에 수산화칼슘을 통한 치근단유도술을 시도하였고, 3년간 주기적 내원을 통해 치료한 결과 치근의 근심면의 비정형적 발달을 보였다. 현재 이 치아는 임상증상과 방사선 사진을 통해 확인한 결과 특이한 염증소견 없는 예후를 보이고 있기에 보고하는 바이다.

• Journal of Periodontal and Implant Science
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• 제32권3호
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• pp.539-554
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• 2002

It has been approximately 40 years since $Br{{\aa}}nemark$ first introduced osseo-integration for implants in the early 1960s. Unlike crown and bridge or denture treatment, implant treatment helps preserve existing bone and improve masticatory functions. Thus, the awareness of implant treatment has grown rapidly among dentists and patients alike in Korea, as it becomes a widely accepted treatment. The following results on patients type and implant distribution were compiled from 1814 implant cases of 640 patients treated at the periodontal dept. of Y University Hospital during 1992 to 2001. 1. There are no dissimilarities between men and women, with patients in their 40,50s accounting for 49% of patients and 56% of implant treatments; the largest share of patients and implant treatments. 2. Mn. posterior area accounted for 59% of implant treatments followed by Mx. posterior area(21%), Mx anterior area(l4%) and Mn anterior area 2%. 3. Partial edentulous patients treated by single crown and bridge-type prosthesis accounted for 98% and fully edentulous patient accounted for the remaining 2% 4. The major cause of tooth loss is periodontal disease, followed by dental caries, trauma and congenital missing. Compared to women, men are more likely to suffer from tooth loss due to periodontal disease. Also, older people are more likely to suffer from tooth loss due to periodontal disease rather than dental caries. 5. The distribution of bone quality for maxillae was 52% for type III, followed by 23% for type II, 20% for type IV and 0% for type I. As for mandible, the distribution was 52% for type II, followed by 37% for type III, 7% for type IV and 4% for type I. 6. The distribution of bone quantity for maxillae was 49% for type C, followed by 34% for type B, 14% for type D, 3% for type A, and 0% for type E. As for mandible, the distribution was 52% for type B, followed by 35% for type C, 6% for type D, 3% for type A and 0% for type E. 7. The majority of implants were those of 10-14mm in length (80%) and regular diameter in width (79%). The results provided us with basic data on patient type, implant distribution, bone condition, etc. We wish that our results coupled with other research data helps assist in the further study for better implant success/survival rates, etc.

• 대한치과보철학회지
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• 제37권2호
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• pp.143-166
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• 1999

The success of porcelain laminate veneer depends on the bond strength between tooth structure and ceramic restoration and the design of tooth preparation. In particular, incisal coverage and incisal finish line are the two most important factors in long-term fracture resistance. Although the majority of clinicians are practicing incisal coverage and there are various opinions on the geo-metrical ratio between the clinical crown length of the remaining tooth structure and the length of incisal extension in porcelain laminate veneer and the optimal incisal finish lines. scientific evidence still loaves much to be desired. The purpose of this study was to determine the effects of the amounts of incisal coverage and the types of incisal finish line on the stress distribution in maxillary anterior porcelain laminate veneers under two different loading conditions. Three-dimensional finite element models of a maxillary anterior porcelain veneer with differ-ent amounts of incisal coverage ; 0, 1, 2, and 3mm and different incisal finish lines feathered edge, incisal bevel, reverse bevel and lingual chamfer with various amounts of lingual extension were developed. 300N force was applied at the point 0.5mm cervical of the linguoincisal edge in two loading conditions ; A) 125 degrees, B) 132 degrees. Tensile and compressive stress in ceramic and shear stress in the resin cement layer were analyzed using three-dimensional finite element method. The results were as follows : 1. The types of incisal finish line had more influence on the stress distribution in porcelain laminate veneer than the amounts of incisal coverage. 2. In case of no incisal coverage, incisal beveled laminate exhibited more evenly distributed tensile stress than feathered edged laminate. And in case of incisal coverage, reverse beveled laminate and lingual chamfered laminate with 1mm lingual extension exhibited more evenly distributed tensile stress than lingual chamfered laminates with 2mm and 3mm lingual extension. 3. As long as the lingual chamfer goes, less tensile stress was found at the incisal edge, while much more tensile stress was found at the lingual margin area in proportion to the length of lingual extension. 4. Under 125 degree load, tensile stress in porcelain laminate veneer had increased compared with that under 132 degree load and the difference exhibited by the change of the amount of tooth support was larger. 5. The types of incisal finish line and the distance from the incisal finish line to the loading point had more influence on the shear stress distribution in the resin cement layer than the amounts of incisal coverage. In contrast loading condition had little influence.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.148-158
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• 1994

The purpose of this study was to compare the adaptation to tooth structure of light - cured glass ionomer cement with that of self -cured glass ionomer cement. In this study, class V cavities were prepared on the buccal surfaces of 10 extracted human premolar teeth, and teeth were randomly assigned 2 groups of 5 teeth each. The cavities of self-curing glass ionomer cement group were restored with the Fuji n. and the cavities of lightcuring glass ionomer cement group were restored with the Fuji II LC. The surfaces of glass ionomer cements were applied with All-Bond 2 adhesive, and cured with visible light. The restored teeth were stored in 100% relative humidity at $37^{\circ}C$ for 24 hours. And then. the roots of the teeth were removed with the tapered fissure bur and the remaining crowns were sectioned occlusogingivally through the center of glass ionomer restorations. Adaptation at tooth-restoration interface was assessed occlusally. axially, and gingivally by scanning electron microscope. The results were as follows : 1. On the occlusal margin, the group of self - curing glass ionomer cement showed closer adaptation to both enamel and dentin than the group of light-curing glass ionomer cement showing 5/lm gap between cement and tooth structure. 2. On the axial wall. the group of light-curing glass ionomer cement showing 5-$7{\mu}m$ gap between cement and dentin showed closer adaptation to dentin than the group of self -curing glass ionomer cement showing 10-$15{\mu}m$ gap between cement and dentin. 3. On the gingival margin, the group of light-curing glass ionomer cement showing 2-$5{\mu}m$ gap between cement and dentin(X 1200) showed closer adaptation to dentin than the group of self-curing glass ionomer cement showing 20pm gap between cement and dentin(X 600). 4. The group of self -curing glass ionomer cement showed closer adaptation on the occlusal margin than on the gingival margin, and the group of light-curing glass ionomer cement showed similar adaptation on both occlusal and gingival margins.

• 한국치위생학회지
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• 제19권1호
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• pp.55-64
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• 2019

Objectives: The purpose of this study was to compare the differences in oral health-related quality of life among elderly people aged over 65 years, in terms of physical, mental and oral health status and to analyze factors affecting their oral health-related quality of life. Methods: From May 9 to June 23, 2017, we randomly visited aged-care community centers in the metropolitan area, and recruited 222 elderly, aged 65 or older. First, each participant completed a questionnaire consisting of 4 general items: 1 systematic disease, and 3 subjective oral conditions. Afterwards, the researchers interviewed the participants to assess their mental status, using MMSE-DS and recorded the responses. Finally, an oral examination was performed to determine the number of remaining teeth. The average oral health-related quality of life according to each characteristic was analyzed by t-test and ANOVA. Hierarchical multiple regression analysis and Pearson's correlation coefficient analysis were used to analyze the correlations between factors and the factors affecting oral health-related quality of life. Results: The mean oral health-related quality of life was 4.15. Participants with 20 or more remaining teeth demonstrated better oral health-related quality of life than those with 19 or less teeth. Higher oral health-related quality of life was also found among elderly without gingival bleeding, self-reported halitosis and dry mouth. In addition, positive correlation with the number of remaining teeth and negative correlation with gingival bleeding, self-reported halitosis and dry mouth, were noted. Finally, the results of the hierarchical multiple regression analysis indicated that remaining teeth, gingival bleeding, self-reported halitosis and education were influential factors in determining the oral health-related quality of life among the elderly. Conclusions: The results of this study confirmed the necessity of better policy support, and the importance of implementing delivered, elderly-centered oral health education program by professionals to prevent tooth loss and manage periodontal diseases.

• 대한소아치과학회지
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• 제26권3호
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• pp.479-485
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• 1999

복합레진을 이용한 수복은 재료의 낮은 강도와 중합수축으로 인한 변연 누출 그리고 상아질과의 결합력 등으로 인해 제한된 범위에서만 사용되었으나, 최근 물성의 향상 및 상아질 결합제의 발달로 심미수복이 필요한 여러 부위에 이용되고 있다. 반직접법을 이용한 레진 인레이는 와동의 크기가 너무 크거나 직접 수복이 곤란한 경우 사용될 수 있으며, 어린 환자의 영구구치 수복시 적절한 비용으로 가급적 오랫동안 보철치료를 받지 않고 사용할 수 있도록 한다. 반직접법의 장점으로는 중합수축으로 인한 변연누출이 적고, 2차 중합을 통해 중합도가 증가하여 강도가 증가되며, 간접법시 필요한 기공실 과정이 불필요하여 1회의 내원으로 치료 가능하다는 것 등이 있다. 본 증례는 심미적 치료를 원하는 환자의 구치부 수복시 반직접법을 이용한 레진 인레이를 사용하여 양호한 치료결과를 얻었기에 이를 보고하는 바이다.

• 치위생과학회지
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• 제18권1호
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• pp.1-8
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• 2018

Stroke is the second cause of death worldwide, although the survival period is increasing after the occurrence of stroke, severe physical disability is caused with aftereffect. Oral inflammation is not limited to the oral cavity, it can cause malignant changes in other tissues and organs. In previous studies, we confirmed the relationship between tooth loss and stroke due to periodontal inflammation. The purpose of this study was to investigate the relationship between oral health and stroke such as oral hygiene behavior, tooth loss and periodontal disease among Korean adults over 40 years of age. This study was analyzed using the 6th Korea National Health and Nutrition Examination Survey (KNHANES) data. A total of 3,389 adults over 40 years of age were analyzed as final subjects. Socioeconomic statuses and oral health status was analyzed using a complex sample analysis technique. Logistic regression was used to analyze the relationship of oral health and stroke, and 95% confidence intervals were computed using SPSS. When the prevalence of stroke according to oral hygiene behavior was checked, the prevalence of strokes was lower in subjects who had a lot of brushings per day and subjects who used oral hygiene products (p<0.05). The risk of stroke was 2.17 times (95% confidence interval, 1.43~3.28) higher in the group with less than 19 remaining teeth, but it was not statistically significant as a result of adjusting for age and sex, income level, education level, drinking and smoking (p>0.05). Loss of teeth was found to be associated with the risk factor of stroke. Therefore, loss of teeth due to periodontal disease is an additional issue that should be considered as a risk factor for stroke.