• 대한소아치과학회지
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• 제24권1호
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• pp.112-124
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• 1997

According to extensive use of composite resin which have superior esthetic property, every effort on improving bonding strength between a tooth and composite resin has been continued. Acid etching technique is a method that micro-etches the tooth surface which provides bonding with composite resin possible. Recently, there were several reports that mechanical treatment obtained from air-abrasion can provide similar bonding strength with acid etching technique. So, this experimental study was designed to compare the shear bonding strength between using air-abrasion technique and using acid etching technique. Initially, bovine teeth were divided into enamel and dentin experimental groups. Respectively each group was categorized into three subgroups. One subgroup was acid etched with 35% phosphoric acid, then bonded with composite resin. The other subgroup was air-abraded with $50{\mu}m$ $Al_2O_3$ particles sprayed with 160psi air pressure using air abrasion unit(KCP-1000, A.D.T., U.SA), and composite resin was bonded. In another subgroup, composite resin was bonded after acid etching following air-abrasion. So, enamel experimental groups were made of E1 (acid etched only), E2(air-abraded only), E3(acid etched following air-abraded), and dentin experimental groups were made of D1(acid etched only), D2(air-abraded only), D3(acid etched following air-abraded). Each subgroup had 10 specimens. Dentin bonding system(Scotchbond Multi-purpose, 3M Co., U.S.A.) and composite resin(Z-100, 3M Co., U.S.A.) were applied on treated surface using 5mm diameter gelatin capsule as manufacturer's direction. After 1200 times thermocycling between $5^{\circ}C$ and $55^{\circ}C$, shear bond strength was measured in 5mm/min crosshead speed with Instron(Instron Co., U.S.A.), and also treated enamel and dentin were observed with SEM(JEOL Co., Japan). The following results were obtained: 1. In the enamel experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 2. In the dentin experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 3. In the SEM study, air-abraded enamel and dentin had irregular and rough surfaces.

• 구강회복응용과학지
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• 제35권4호
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• pp.206-213
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• 2019

목적: 굴곡파절의 대부분 연구들이 협측에 한정되어있다. 본 연구에서는 상악 구치부에서 구개측 굴곡파절의 빈도 조사를 통해 굴곡파절의 원인을 분석해보고자 한다. 연구 재료 및 방법: 총 3193개의 상악 구치를 대상으로 조사를 진행하였다. 구내 관찰과 모형 관찰, 그리고 모형 스캔을 통해 제작된 가상 모형을 관찰하는 방법으로 조사를 진행하였다. 그 결과를 치아, 연령, 성별, 악궁에 따라 분류하였다. 통계적 유의성의 평가를 위해 Chi-square test를 시행하였다(α = 0.05). 결과:상악 소구치(6.8%)보다 대구치(10.8%)에서 구개측 굴곡파절이 높은 빈도로 관찰되었고, 그중 제1대구치(39.1%)에서 가장 높은 빈도로 관찰되었다. 연령이 증가할수록 구개측 굴곡파절이 높은 빈도로 관찰되었으며 이는 통계적으로 유의성이 있었다(P < 0.05). 구개측 굴곡파절의 빈도는 성별에 따른 차이에서는 통계적으로 유의성이 없었으며(P > 0.05), 악궁에 따른 차이에서는 좌측에서 더 높은 빈도로 나타났고 통계적으로 유의성이 있었다(P < 0.05). 결론: 상악 구치에서 구개측 굴곡파절은 상악 제1대구치에서 높은 빈도로 관찰되었고, 연령의 증가에 따라 증가하는 양상을 보였다. 이와 같은 결과는 굴곡파절의 가장 주된 원인이 교합력임을 의미한다.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2001년도 춘계학술대회
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• pp.235-237
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• 2001

;Dentistry has benefited from tremendous advances in technology with the introduction of new techniques and materials, and patients are aware that esthetic approaches in dentistry can change one's appearance. Increasingly. tooth-colored restorative materials have been used for restoration of posterior teeth. Tooth-colored restoration for posterior teeth can be divided into three categories: 1) the direct techniques that can be made in a single appointment and are an intraoral procedure utilizing composites: 2) the semidirect techniques that require both an intraoral and an extraoral procedure and are luted chairside utilizing composites: and 3) the indirect techniques that require several appointments and the expertise of a dental technician working with either composites or ceramics. But, resin restoration has inherent drawbacks of microleakage. polymerization shrinkage, thermal cycling problems. and wear in stress-bearing areas. On the other hand, Ceramic restorations have many advantages over resin restorations. Ceramic inlays are reported to have less leakage than resin restoration and to fit better. although marginal fidelity depends on technique and is laboratory dependent. Adhesion of luting resin is more reliable and durable to etched ceramic material than to treated resin composite. In view of color matching, periodontal health. resistance to abrasion, ceramic restoration is superior to resin restorationl. Materials which have been used for the fabrication of ceramic restorations are various. Conventional powder slurry ceramics are also available. Castable ceramics are produced by centrifugal casting of heat-treated glass ceramics. and machinable ceramics are feldspathic porcelains or cast glass ceramics which are milled using a CAD/CAM apparatus to produce inlays (for example, Cered. They may also be copy milled using the Celay apparatus. Pressable ceramics are produced from feldspathic porcelain which is supplied in ingot form and heated and moulded under pressure to produce a restoration. Infiltrated ceramics are another class of material which are available for use as ceramic inlays. An example is $In-Ceram^{\circledR}$(Vident. California, USA) which consists of a porous aluminum oxide or spinell core infiltrated with glass and subsequently veneered with feldspathic porcelain. In the 1980s. the development of compatible refractory materials made fabrication easier. and the development of adhesive resin cements greatly improved clinical success rates. This case report presents esthetic ceramic inlays for posterior teeth.teeth.

• 대한치과기공학회지
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• 제39권1호
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• pp.43-52
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• 2017

Purpose: Physical and chemical properties of gold is most suitable to be restored of teeth to its original state. Recently zirconia was used instead of gold because of esthetical and intimacy of human body. Because of high strength and high abrasion resistance of zirconia, all zirconia artificial tooth lead to wear the original tooth of opposite site. To preserve this original tooth, zirconia artificial tooth covered with dental ceramic glass was used. When joining the zirconia core and dental ceramic glass, difference of their thermal expansion coefficient and wetting ability is generated the residual stress at interface lead to crack. In order to solve this problem, intermediate layer what is called zir-liner was imported to decrease the residual stress and increase the bonding strength. Methods: In this study, to identify the optimum conditions for manufacturing process, various methods to rough the surface of zirconia core were adopted, and vary the thickness of interlayer, and analyzed bond strength. Results: Bond strength of sanding specimens group showed higher than that of non-sanding specimens group, and once applied intermediate layer with sanding specimens showed highest bond strength with 28 MPa. SEM photomicrographs of zirconia cores fired at $1500^{\circ}C$ showed parallel straight lines in sanding and pockmarked surface in blasting surfaces as abrasion traces. Observation of the destruction section after shear test by SEM were carried out. Liner applied non-sanding group and non-liner applied sanding group all showed interfacial crack. Sandblasting group with non-liner showed remained dental ceramic glass on the surface of zirconia. Sandblasting group with once applied liner showed partially remained liner and dental ceramic glass on the surface of zirconia. XRD analysis revealed that sandblasting group showed higher monoclinic peaks than other specimens group and this result was due to the high collision energy for stress induced phase transformation. Conclusions: A study on the improvement of bonding strength between zirconia and dental ceramic glass steadily carried out for the future to practical use.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.479-489
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• 1997

The purpose of this study was to evaluate the effect of the Nd : YAG laser on the tooth hypersensitivity by the observation of the morphological changes of the dentinal surface irradiated with Nd : YAG laser by use of SEM. In 40 mandibular and maxillary molars without any carious lesion or restoration, severe attrition and abrasion, Enamel was removed with fine grit diamond bur and exposed dentinal surfaces were polished with Soflex discs. In control group (10 teeth), exposed dentinal surfaces were acid-etched with 10 % Maleic acid for 15 seconds. In the experimental group 1 (10 teeth), acid-etched dentinal surfaces with 10% Maleic acid were prepared by Nd : YAG laser (6 watts power, 1 psi water, 18 psi air) for 2 minutes. In the experimental group 2 (10 teeth), exposed dentinal surfaces were irradiated with Nd: YAG laser (10 watts power, 3 psi water, 10 psi air) until the painted black stains on the dentinal surfaces were completely removed. In the experimental group 3 (10 teeth). dentinal surfaces were prepared with Nd : YAG laser (6 watts power, 1 psi water, 18 psi air) until the painted black stanins on them were completely removed and then the irradiated dentinal surfaces were acid-etched with 10 % Maleic acid for 15 seconds. The specimens were routinely processed and observed with scanning electron microscope. The results were as follows : 1. In the irradiated dentinal surfaces, the characteristics of the melting and recrystalization on the dentinal surfaces were observed. Compared with the results in the control group, we could observe that in the irradiated dentinal surfaces, the aperture of the dentinal tubules were reduced and there were more debris obstructing the dentinal tubules. 2. In the irradiated dentinal surfaces, crater structures were commonly present and in the crater bottoms, there were a lot of bead like melted dentin structures, which had the ruptured opening in the center of them. 3. The melted dentins and cracks in the smear layer were less frequently observed in the irradiated dentinal surfaces using copious cooling water than in the irradiated dentinal surfaces using scare cooling water.

• 대한장애인치과학회지
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• 제15권1호
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• pp.45-49
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• 2019

Bartter 증후군은 심각한 헨레고리 비후 상행각(TAL)에서의 일차적인 염류(NaCl) 수송 장애로 인하여 심각한 저칼륨혈증을 특징으로 하는 질환이다. 만성 구토로 인한 치아의 부식, 교모, 마모의 구강 내 소견을 보여 구토와 관련된 적절한 칫솔질 및 식이 습관 등에 대한 정기적인 교육과 관찰이 권장되며 교합고경의 회복을 위해 전장관 수복이 추천된다. 치과 치료 시의 스트레스로 인하여 전해질 수치의 불균형이 초래될 가능성이 있어 전신마취 하 치료가 유리할 수 있으며, 전신마취 시 과환기되어 저칼륨혈증이 심화되지 않도록 지속적인 감시를 해야하고 술 후에도 전해질 불균형이 초래되지 않도록 지속적인 감시가 필요하다.

• 동력기계공학회지
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• 제12권3호
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• pp.38-43
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• 2008

The usage of electric forklift truck is gradually increasing due to the convenience at conveying and arranging the materials in the industrial field. In this study, the author designed and suggested the optimum driving system and load tester which both of them are the most important part of the forklift truck. The planetary gear is chose to driving system because it makes big power even though the motor size is small. The gear teeth of planetary gear were designed and the designed planetary gear was tested considering the yield strength and the abrasion of gear teeth. The B-Type electric brake which consists of multiple plates and operates with non-magnetic type was connected with a single shaft in the driving system. So, it can be applied at the sudden braking situation which has the torque increment. And it has the compact size and excellent durability Load tester can give the various levels of load to the planetary gear of driving system in the electric forklift truck and it can also measure the levels of the load which were applied. Therefore, we can measure the noise, torque and perform the durability, vibration tests using load tester. It will be economical because many kinds of test can be performed using reasonable priced load tester The driving system of electric forklift truck which has sufficient competitive can be manufactured using our designed planetary gear reducer with reasonable price. The designed load tester can use for checking the performance of other reducers, as well.

• 대한치과보철학회지
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• 제54권2호
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• pp.160-166
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• 2016

정상적인 수준의 생리적 마모는 수정이 필요 없으나, 치아 경조직의 상실 속도가 비정상적으로 빠른 경우에는 치아에 심각한 손상을 야기하고 심미적, 기능적 구조를 파괴할 수 있다. 전반적인 치아 마모를 보이는 환자의 치료를 위하여 전악을 보철로 수복하고, 교합거상이 필요할 수도 있지만, 마모된 전치부의 보철 수복을 위한 가용공간 때문에 수직교합고경에 변화를 주는 경우가 아니면 잘 변경시키지 않는다. 본 증례의 환자는 마모된 치열과 치관 파절을 주소로 내원한 74세 남자 환자이다. 임상검사 결과 구치부 지지에 의해 수직고경의 감소가 없음을 확인하고 수직고경 변화 없이 전악 수복하여 만족할 만한 결과를 얻었기에 이를 보고하고자 한다.

• 구강회복응용과학지
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• 제31권3호
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• pp.231-241
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• 2015

환자의 심미적 요구가 증가함에 따라 전치뿐만 아니라 구치부에서도 자연치아와 유사한 색조와 외형을 재현한 보철물에 대한 필요성이 증가하고 있다. 단일 지르코니아와 CAD/CAM 시스템을 통해 이러한 환자의 요구를 만족시키는 보철물 제작이 가능해졌다. 본 증례는 70세 여자환자로 전치부 보철물이 깨져서 보기 싫고 하악 구치부가 없어서 저작이 불편하다는 주소로 내원하였다. 하악 구치의 상실로 교합평면이 붕괴되었으며 과도한 치아 마모 및 수직고경 상실이 관찰되어 치아 상실 부위에 임플란트를 식립하고 수직고경 증가와 함께 지르코니아 고정성 보철물을 이용한 전악 수복 치료를 진행하였다. 치료 후 3년 간 이상적인 교합이 잘 유지되고 기능적, 심미적으로 만족한 결과를 얻었기에 이를 보고하는 바이다.

• Journal of Oral Medicine and Pain
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• 제25권2호
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• pp.253-263
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• 2000

We collected age determination cases which were done at Yonsei university dental hospital, department of oral medicine from 1976 to 1999 to analyze it's tendency among Koreans. We analyzed 435 clients cases which were stored by age estimation program from January 1993 to December 1999. The results are as follows: 1. There were no significant difference in the sexual distribution (male : 52.0%, female : 48.0%) and more than half percent (51%) were 20's and 30's. 2. Among the age determination clients, those who wanted to decrease their age (50.3%) and those who wanted to increase their age (49.7%) shows similar in number. And the former case were predominant in the female clients, but the latter case in the male clients. Also the clients below six years of age were predominant in the former case, but the clients more than sixty were predominant in the latter case. 3. The purposes of age correction showed different distribution for ages: job or employment for 20's and 30's, marriage for 20's, registration for school for below six, welfare and other social services for 50 and older. 4. Age was estimated by Nolla's growth stage for 12 and under, calcification of the second and third molar for 12~20, and for 20 and over, Takei's tooth abrasion model was used. 5. The alleged age was in accordance with the documents and other information given by clients, but in the 20.6% of the estimation cases, the alleged age was discarded. In the results of the analysis of age determination cases in Koreans, many of the cases resulted from our historical turbulence and social distinctiveness, causing an increase in the necessity for age correction in each age group. For more accurate determination for each age group, further studies with Koreans must be done continuously.