• 대한치과보철학회지
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• 제42권1호
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• pp.11-20
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• 2004

Problem : The several studies were reported to the effects of individual tooth tray with the parallel tooth, but not reported to the effect of individual tooth tray with severe undercut in impression making. Purpose : The purpose of this study is to examine the effect of individual tooth tray; 1) the accuracy of impression in terms of distance. 2) reproducibility of pocket. Material and methods : In this study, a metal model with 3 teeth including tooth prepared 30-degree undercut and gingival crevice of the depth 5mm, width 0.4mm was cast. Impressions of the metal model were taken in 5 times used 4 kinds of impression materials with individual tooth tray and another impression taking were made with conventional method without individual tooth, used same materials, procedure. The stone models were made. Distances between abutments were measured with a Micromeasurescoup-mm. Result : The following results were obtained ; 1. In the comparisonof inter-abutment distance between parallel tooth without individual tooth tray, 4elastomeric materials have not significant difference to the metal model(p>0.05). 2. In the comparisonof inter-abutment distance with undercut tooth without individual tooth tray, 4elastomeric materials have a significant difference to the metal model(p<0.05), especially polyether's dimensional change is large. 3. If individual tooth tray was used to take impression in abutment teeth with severe undercut, more stable results was achieved easily than conventional method. (p>0.05). 4. It is not true that the pressure of impression material with individual tooth tray increased to gingival sulcus. Conclusion : By the results, I knew the fact that individual tooth tray was useful impression method on the teeth with severe undercut for the dimensional stability. Also, I could not confirm the fact that individual tooth tray would increase the penetrating pressure into cervice.

• 대한소아치과학회지
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• 제34권2호
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• pp.315-321
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• 2007

어린이의 공간유지와 교합유도의 치료를 위하여 가철성 장치는 소아치과 임상에서 일상적으로 사용되고 있다. 상악의 경우와는 달리 하악에서는 가철성 장치를 사용하는데 있어 유지력의 저하에 따른 치료효과의 감소, 환자의 불편감과 거부감으로 인한 미착용 등의 문제가 흔히 발생한다. 이것은 유치열기나 초기 혼합치열기 어린이의 경우, 하악구치부의 undercut양이 충분치 못함에도 불구하고, 여기에 협측 undercut으로부터 유지력을 얻는 각종 clasp를 적용하기 때문으로 사료된다. 또한 전통적인 가철성 장치들의 acrylic base plate가 설측에 위치하고 있어 설측 연조직이나 치조능 undercut과 많은 문제를 일으키는 현상을 볼 수 있다. 어린이들은 하악 장치의 작업모형을 위한 인상채득과정에서 술자의 지시대로 혀를 바르게 거상하지 못하는 예가 많은 것도 그 원인요소로 들 수 있다. 본 연구는 전통적인 하악의 Hawley acrylic plate로부터 clasp와 acrylic baseplate의 위치를 바꾸어 협측 base plate와 설측 clasp을 이용한 buccal acrylic appliance를 유치열기 및 초기 혼합치열기 어린이의 구강에 적용하여 그 장단점을 조사하고 환아들의 수용도와 효율성을 기존의 lingual acrylic appliance와 비교, 검토할 목적으로 시행되었다. 공간유지 및 치아이동을 필요로 하는 5개 증례를 대상으로 각 증례에 buccal acrylic appliance와 기존의 lingual acrylic appliance를 모두 적용하여, 유지력, 환자 수용도, 혀의 기능과의 조화, 치료 효과 등의 측면을 상호 비교해 보았다. 조사 결과, 조사 대상의 모든 증례에서 유지력과 환아의 수용도 측면에서 협측 장치가 설측 장치에 비해 월등히 우수한 것으로 나타났다. 또한 치료 효과의 측면에서도 협측 장치는 설측 장치와 유사한 것으로 나타났다. 본 연구를 통하여 하악에 가철성 장치를 사용할 경우, 전통적인 설측 장치와 관련된 각종 부작용을 해결하는 데에 buccal acrylic appliance가 훌륭한 대안으로서 임상적용을 추천할 만 하다고 사료되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.837-841
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• 1996

It is the eccentricity that determines most of the characteristics of the elliptic gears. Accoding to the theoretical tooth profiles, two pairs of the elliptic gears were manufactured by using CNC wire cutting machine. For harmonious rotating motion, it is necessaryto consider operating pressure angle and module not to generate undercut. The characteristics of vibration were investigated by analyzer.

• 한국정밀공학회지
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• 제15권5호
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• pp.85-92
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• 1998

This present paper describes a mathematical model of profile shifted elliptical gears, and this model is based on the concepts of envelope theory and conjugate geometry between the blank and the straight-sided rack cutter. The geometric model of the rack cutter includes working regions generating involute curves and fillets for trocoidal curves, and furthermore the addendum modified coeff. is considered for avoiding undercutting. The addendum modified coeff. is changed linearly along with pitch curves and must be the same absolute value at both major semi-axis and minor semi-axis. If undercutting is at all pronounced, the undercut tooth not only are weakened in strength, but lose a small portion of the involute adjacent to the base circle, then this loss of involute may cause a serious reduction in the length of contact. A very effective method of avoiding undercutting is to use the so-called profile shifted gearing. Non-undercutting condition is examined with the change of eccentricity and addendum modified coeff. in elliptical gears and then the minimum number of tooth is proposed not to gernerate undercutting phenomenon.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.572-577
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• 1997

This present paper describes a mathematical model of profile elliptical gears, and this model is based on the concepts of envelop theory and conjugate geometry between the blank and the straight-sided rack cutter. The geometric model of the rack cutter includes working regions generating involute curves andd fillets for trocoidal curves, and furthermore the addendum modified coeff,is considered for avoiding undercutting. The addendum modified coeff, is changed linearly along with pitch curves and must be the must be the same absolute value at both major semi-axis and minor semi-axis. If undercutting is at all pronounced, the undercut tooth not only are weakened in strength, but lose a small portion of the involute adjacent to the base circle, then this loss of involute may ncause a serios reduction in the length of contact. A very effective method of avoiding undercutting is to use the so-called profile shifted gearing. Non-undercutting conditon is examined with the change of eccentricity and addendum modefied coeff. in elliptical gears and then the minimum number of tooth is proposed not to gernerate undercutting phenomenon.

• 대한소아치과학회지
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• 제26권2호
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• pp.207-217
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• 1999

본 연구의 목적은 어린이에게 사용되고 있는 가철식 교정장치를 위한 clasp에 대하여 각 디자인간 유지력의 차이를 평가하고자 함이다. 상악 유견치와 제 1, 2유구치 및 제 1 대구치를 단일 치아모형과 두 개의 인접 치아 형태로 금속 주모형을 제작한 후 clasp를 종류에 따라 형성하여 각 모형에 대한 clasp의 유지력을 측정하였다. Clasp의 종류에 따른 유지력을 서로 비교하여 다음과 같은 결론을 얻었다. 1. 단일치아에서 유지력을 얻는 clasp중 Jackson clasp와 Adams clasp는 다른 clasp에 비하여 높은 유지력을 나타냈으며, C clasp는 가장 낮은 유지력을 나타냈다(p<0.05). 2. 두개 이상 치아의 치간부 undercut을 이용하는 clasp중 eyelet clasp가 가장 큰 유지력을 보여주었고 triangular clasp, ball clasp순으로 낮은 유지력을 보여주었다(p<0.05).

• 대한치과보철학회지
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• 제35권3호
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• pp.470-485
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• 1997

A fundamental principle in clasp selection for a specific abutment is the reduction of the transmission of excessive forces to the abutment tooth. Those forces include tilting, tipping, and stress on the abutment tooth. The flexibility of a clasp was believed to directly affect the reduction of such forces. Opinions have been expressed concerning the proper type of clasp to be used to prevent stress on periodontium. In order to evaluate and compare the various designs of a clasp system, it is necessary to measure these forces. This study compared the average measurements of forces required to dislodge three kinds of circumferential clasps having different amount of undercuts : the first with a round retentive arm, the second with a half round retentive arm, the third with a wrought wire retentive arm under tensile load. Three commonly used undercuts( 0.01, 0.02, 0.03 inch) were created on nine cast crowns, premolars and molars. The test was run six times for a same clasp. The means of tensile load required to dislodge each of the different clasps were compared statistically using the ANOVA test and multiple range test (Duncan test). The results were as follows. 1. The amount of tensile load of the wrought wire clasp was significantly different from the cast round or half round clasp (p<0.05). 2. The more amount of the undercut, the more tensile load was needed to dislodge the clasps. There were significant differences among them (p<0.05). 3. The molar showed higher tensile load than the premolar, and there was significant difference (p<0.05). 4. The means of tensile load according to clasp types showed significant differences at the molar between wrought wire clasp and cast clasp (p<0.05), but did not at the premolar.

• The Journal of Advanced Prosthodontics
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• 제11권2호
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• pp.138-146
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• 2019

PURPOSE. Comparing the accuracy of casts produced from digital workflow to that of casts produced from conventional techniques. MATERIALS AND METHODS. Whole arch alginate (ALG) and polyvinyl siloxane (PVS) impressions were taken with stock trays and custom trays, respectively. The ALG impressions were poured with type III dental stone, while the PVS impressions were poured with type IV dental stone. For the digital workflow, IOS impressions were taken and physical casts were produced by 3D printing. In addition, 3D printed casts were produced from images obtained from a laboratory scanner (LS). For each technique, a total of 10 casts were produced. The accuracies of the whole arch and separated teeth were virtually quantified. RESULTS. Whole arch cast accuracy was more superior for PVS followed by LS, ALG, and IOS. The PVS and ALG groups were inferior in the areas more susceptible to impression material distortion, such as fossae and undercut regions. The LS casts appeared to have generalized errors of minor magnitude influencing primarily the posterior teeth. The IOS casts were considerably more affected at the posterior region. On the contrary, the IOS and LS casts were more superior for single tooth accuracy followed by PVS and ALG. CONCLUSION. For whole arch accuracy, casts produced from IOS were inferior to those produced from PVS and ALG. The inferior outcome of IOS appears to be related to the span of scanning. For single tooth accuracy, IOS showed superior accuracy compared to conventional impressions.

• 대한치과교정학회지
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• 제27권1호
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• pp.157-171
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• 1997

TiN ion-plating이 교정용 브라켓의 접착강도에 미치는 영향을 알아보기 위하여 세 종류의 서로 다른 기저면형태를 가지는 스테인레스 스틸제의 브라켓을 선택하고, TiN ion-plating 된 브라켓과 ion-plating 되지 않은 브라켓을 치아에 접착시켰을 때 초기 및 장기접착강도, 접착계면의 주사전자현미경 관찰, 파단면의 주사전자현미경 관찰을 비교 분석하여 다음과 같은 결론을 얻었다. ${\cdot}$ TiN ion-plating을 하지 않은 경우 24 시간 후의 접착강도는 Micro-Loc형이 $5.89{\pm}1.77MPa$, Foil Mesh형이 $4.27{\pm}1.12MPa$, Undercut형이 $2.64{\pm}0.58MPa$로 Micro-Loc형 이 가장 높았고, 그 다음이 Foil Mesh형 그리고 Undercut 형의 순으로 나타났다(P<0.05). ${\cdot}$ TiN ion-plating시 24시간 투의 접착강도는 Micro-Loc형이 $6.26{\pm}1.51MPa$, Foil Mesh형이 $7.45{\pm}2.01MPa$, Undercut형 이 $2.93{\pm}0.84 MPa$로 ion-plating 하지 않은 경우와 달리 Foil Mesh형이 Micro-Loc형보다 오히려 높게 나타났고, Undercut형이 역시 가장 낮은 접착강도를 나타내었다(P<0.05). Ion-plating 유무에 따른 24시간 후의 접착강도는 3가지형 모두에서 ion-plating시 증가하였으나 Foil Mesh형에서만 유의한 증가가 있었다(P<0.001). ${\cdot}$ 장기침적시 ion-plaling의 유무에 관계없이 전반적으로 초기(1일)접착강도보다 증가하였으며 접착력의 안정성을 나타내었다. ${\cdot}$ 접착계면의 주사전자현미경 관찰 결과 브라켓 기저면의 형태나 ion-plating 유무에 관계 없이 레진이 브라켓 기저면으로 잘 퍼져들어가 브라켓과 치아와의 사이에 견고한 접착면을 나타내었고, 장기침적의 경우도 같은 양상을 나타내었다. ${\cdot}$ 파단면의 주사전자현미경 관찰에서는 다양한 파괴 양상이 나타났다.

• 한국생산제조학회지
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• 제21권2호
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• pp.283-289
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• 2012

Cam rack pinion (CRP) system which consists of cam rack and roller pinion transforms the rotation motion into linear one. The roller pinion has the plurality of rollers and meshes with its conjugated cam rack. The exact tooth profile of the cam rack and the non-undercut condition to satisfy the required performance have been proposed by introducing the profile shift coefficient. The load stress factors are investigated by varying the shape design parameters to predict the gear surface fatigue limit which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.