• 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.

• 대한치과보철학회지
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• 제41권4호
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• pp.405-420
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• 2003

Purpose : The purpose of this study was to compare the fracture resistance of the IPS Empress ceramic crown with 1.0mm width rounded shoulder, which is usually recommended in all ceramic crown. and 0.5mm width chamfer finish lines on the maxillary central incisor. Material and method : After 15 metal dies were made for each group, the IPS Empress all ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan) on the metal die. The cemented crowns were mounted on the positioning jig and the universal testing machine(Zwick Z020, Zwick Co. Germany)was used to measure the fracture strength with loading on the incisal edge. And also, three-dimensional finite element stress analysis was used to measure the stress distribution with the various types of the finish lines(1.0mm width rounded shoulder, 0.5mm width chamfer), the loading site(incisal edge, incisal $\frac{1}{3}$) and the type of loading(concentration loading, distribution loading). Results and conclusion : 1. In the fracture resistance experiment according to the finish line, the mean fracture strength of rounded shoulder(876N) and the mean fracture strength of chamfer(882N) did not skew any significant difference between each other(p>0.05). 2. The stress distribution of all ceramic crown in three dimensional finite element analysis showed concentration aspect at loading point and cervical area or labial surface. 3. In metal die, there were no differences in stress distribution between finish lines, but in natural teeth model, chamfer finish line showed higher stress than rounded shoulder finish line. 4. When force was loaded on the incisal edge the stress was concentrated on the incisal edge and the cervical area of labial surface. When force was loaded on the incisal $\frac{1}{3}$, the stress concentrated on the cervical area of labial surface and the cingulum area. 5. Generally, natural teeth model showed higher and various stress than the metal die.

• 구강회복응용과학지
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• 제19권3호
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• pp.219-237
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• 2003

he purpose of this study was to compare the fracture resistance of the IPS Empress ceramic crown with 1.0mm width rounded shoulder, which is usually recommended in all ceramic crown, and 0.5mm width chamfer finish lines on the maxillary first premolar. 30 sound maxillary first premolars were selected and then storaged in 5% NaOCl and saline. 15 teeth were performed preparation for each group(1.0mm rounded shoulder, 0.5mm chamfer). After 30 stone dies were made for each group, the IPS Empress ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan) on the natural teeth. The cemented crowns were mounted on the positioning jig and the universal testing machine(Zwick Z020, Zwick Co., Germany)was used to measure the fracture strength, with stress loading on the occlusal surface between buccal and lingual cusp. And also, three-dimensional finite element model was used to measure the stress distribution with two types of the finish lines(1.0mm rounded shoulder, 0.5mm chamfer) and two loading conditions(both buccal and lingual cusp inclination, lingual cusp inclination only). The result of the this study were as follows. In the fracture resistance experiment according to the finish line, the mean fracture strength of rounded shoulder(842N) showed higher value than that of the chamfer(590N) (p<0.05). In the three dimensional finite element analysis of all ceramic crown, metal die and natural teeth model did not show any differences in stress distribution between finish lines. Generally, when force was loaded on the occlusal inclination of buccal and lingual cusp, the stress was concentrated on the loading point and the central groove of occlusal surface. When force was loaded only on the occlusal inclination of lingual cusp, the stress was concentrated on the lingual finish line and loading point.

• 대한치과보철학회지
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• 제52권4호
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• pp.305-311
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• 2014

목적: 다양한 원인으로 발생된 Abfraction 병소가 있는 치아를 금속도재관으로 수복 할 경우, 변연의 위치에 따라 예후가 다양해질 수 있다. 수복물의 장기적 성공을 검증하기 위해서는 응력분포의 분석이 필요하지만 금속도재관이 abfraction 병소의 적응증인 경우 금속도재관이 응력 분포에 미치는 영향을 밝히는 연구는 아직 없다. 본 연구의 목적은 abfraction 병소가 있는 치아를 수복하는 금속도재관이 바람직한 응력 분포를 나타낼 수 있는 조건을 알아 보고자 함이다. 재료 및 방법: 치아, 주위 조직과 금속 도재관의 외형을 반영한 2차원 유한 요소모델을 제작하고 144 N의 편심 교합력 하에서의 응력분포를 유한요소 분석법으로 분석하였다. 금속 도재관의 변연 위치를 쐐기모양의 결손부의 하연에(Group 0), 그리고 결손부의 하연보다 1 mm 하방(Group 1)과 2mm 하방(Group2)에 위치시켰다. 결과: Group 0에서 von Mises stress는 금속 도재관의 변연과 결손부의 첨부에 집중 되었고 협측 변연의 응력은 설측 부위로 분포되었다. Group 1과 Group 2에서의 응력분포양상은 비슷하게 나타났다. 응력은 결손부의 첨부에 집중되지만 협측과 설측의 응력띠는 서로 분리된 양상으로 나타났다. 결론: 금속도재관의 변연을 Abfraction 병소의 하연에 설정할 경우, 금속도재관은 Abfraction 병소의 첨부에 응력을 집중시킨다.

• 대한치과보철학회지
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• 제35권4호
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• pp.742-766
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• 1997

The purpose of this study was to determine the effect of finish line design, amount of incisal reduction, and loading condition on the stress distribution in anterior all-ceramic crowns. Three-dimensional finite element models of an incisor all-ceramic crown with 3 different finish line designs : 1) shoulder with sharp line angle 2) shoulder with rounded line angle 3) chamfer : and 2 different incisal reductions : 2mm and 4mm were developed. 300 N force with the direction of 45 degree to the long axis of the tooth was applied at 3 different positions : A) incisal 1/3, B) incisal edge, C) cervical 1/5. Stresses developed in ceramic and cement were analyzed using three-dimensional finite element method. The results were as follows : 1. Stresses were concentrated in the margin region, which were primarily compressive in the labial and tensile in the lingual. 2. Stresses were larger in the area near line angle than on the crown surface of the margin region. In case of shoulder with sharp line angle, stresses were highly concentrated in the porcelain near line angle. 3. At the interface between porcelain and cement and at the porcelain above the margin on crown surface, stresses were the highest in chamfer, and decreased in shoulder with sharp line angle and shoulder with rounded line angle, respectively. 4. At the interface between cement and abutment on crown surface, stresses were the highest in shoulder with sharp line angle, and decreased in shoulder with rounded line angle and chamfer, respectively. 5. The amount of incisal reduction had little influence on the stress distribution in all-ceramic crowns. 6. When load was applied at the incisal edge, higher stresses were developed in the margin region and the incisal edge than under the other loading conditions. 7. When load was applied at the cervical 1/5, stresses were very low as a whole.

• The Journal of Advanced Prosthodontics
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• 제3권2호
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• pp.69-75
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• 2011

This study assessed the effect of preparation design on marginal adaptation and also compared the sensitivity and specificity of clinical evaluation techniques for marginal accuracy of cast restorations to stereomicroscopy. MATERIALS AND METHODS. Three Ivorine molar teeth of different designs were prepared. (A)-A complete crown preparation with buccal shoulder and beveled finish line. (B)-A complete crown preparation with chamfer finish line. (C)-A three-quarter crown preparation with proximal boxes and beveled finish line. Twenty four castings were prepared with eight castings for each design respectively. Each casting underwent examination with an explorer, disclosing media, and a stereomicroscope. Stereomicroscopy at a value less than or equal to 30 microns was used as a gold standard to evaluate the significance of different designs on marginal adaptation. Chi-square tests of independence and Kruskal-Wallis were used to evaluate the effect of preparation design and compare the agreement between examination methods for detection of marginal gap size of greater than or equal to 30 microns (${\alpha}$=.05). Sensitivity and specificity for explorer and disclosing media as compared to stereomicroscope was calculated using statistical formula given by Park. RESULTS. The preparation design did not significantly affect overall marginal adaptation. Examination by explorer and disclosing media at $30 \;{mu}m$ revealed 39% and 10.06% sensitivity and 91% and 82% specificity respectively. CONCLUSION. Preparation designs examined in this study did not significantly affect the marginal adaptation of the castings. Commonly used clinical evaluation techniques using explorer and disclosing media appeared to be inadequate for assessment of marginal accuracy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.771-774
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• 2000

RP techniques have inherent disadvantages caused by their working principles: stair-stepped surface of parts due to layer-by-layer stacking of layers, low build speed caused by line-by-line solidification to finish one layer, and post processing to improve surface finish, etc. The objective of this study is to propose a new RP technique, variable deposition manufacturing (VDM), which can make up for the disadvantages of the existing RP techniques, and to develop an apparatus to implement the technique. The proposed process can greatly reduce the building time and improve the surface finish of parts generated. The experiments are carried out to obtain the range of temperature of molten material to maintain its fluidity and to investigate the effect of gas cooling on the preservation of the slopes. Based on the results, some simple shapes such as a line-shape. an S-shape, and a circle-shape were fabricated from Ethylene Vinyl Acetatecopolymer (EVA). In order to examine the applicability of VDM to more general shapes, a tensile specimen and a yo-yo shape were manufactured by the proposed RP method using EVA material as the first trial approach. The present basic study has shown the possibility of a practicable utilization of the proposed VDM process to prototyping of a general three-dimensional shape.

• 대한치과보철학회지
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• 제36권6호
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• pp.789-805
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• 1998

The purpose of this study was to compare the microleakage of the IPS Empress ceramic crown according to 1) margin types such as rounded shoulder and bevel, 2) margin locations such as enamel and dentine, 3) resin cement types such as Variolink and Bistite. For this study, 80 extracted premolar teeth were used. After 10 experimental dies were prepared for each group, the IPS Empress ceramic crowns were fabricated on the dies and cemented with one of two types of resin cement. After 1,000 cycles of thermal changes were given with the thermocycling unit, each specimen was sectioned with a low speed diamond saw in both the buccolingual and the mesiodistal direction. The microleakage was then measured with a stereo microscope. The obtained results were as follows : 1. Every experimental group showed microleakage. The microleakage of the crowns which had a rounded shoulder on enamel cemented with Variolink was the lowest of all. The resulting rank of the mean microleakage was rounded shoulder on enamel using Variolink(0.601mm), rounded shoulder on enamel using Bistite (0.794mm), bevel on enamel using Variolink (0.826mm), rounded shoulder on dentine using Variolink(1.054mm), bevel on enamel using Bistite(1.087mm), rounded shoulder on dentine using Bistite(1.176mm), bevel on dentine using Variolink(1.258mm), and bevel on dentine using Bistite(1.467mm). 2. The statistically significant differences in the microleakage were found in 4 cases: rounded shoulder on enamel using Variolink and bevel on dentine using Variolink, rounded shoulder on enamel using Variolink and bevel on dentine using Bistite, rounded shoulder on enamel using Bistite and bevel on dentine using Bistite, bevel on enamel using Variolink and bevel on dentine using Bistite. 3. The microleakage of rounded shoulder finish line was lower than that of bevel finish line. The statistically significant differences were found with respect to the type of finish lines. 4. The microleakage of the finish line on enamel was lower than that of finish line on dentine. The statistically significant differences were found with respect to the location of the finish lines. 5. The microleakage of the Variolink cement was lower than that of the Bistite cement. The statistically significant differences were found with respect to the resin cements.

• 대한치주과학회:학술대회논문집
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• 대한치주과학회 2004년도 제44회 종합학술대회 연제초록
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• pp.18-18
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• 2004

• 한국표면공학회지
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• 제32권3호
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• pp.208-210
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• 1999

A new additive for semi-brightness finish in nickel electroplating, having a quarternary ammonium salt structure, has been developed in this study. The effectiveness of the new additive was tested in laboratory-scale eletroplating tests as well as in a full-scale factory plating line. An examination of the plated surface showed that the new additive is as good as the one produced by the most commonly used additive in the nickel plating industry. The plated surface was examined by SEM, EPMA, and Reflectance Spectroscopy, and was found to be compatible to the one obtained with commercial additives. The new additive has a shelf life comparable with those of other commercially available additives. The additive developed in this study has an excellent potential to be used commercially.