• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.816-820
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• 2007

Novel new red-light emitting perylene fluoroionophore N,N'-dipropyl-1,7-bis(calix[4]azacrown-5-crown-5)- 3,4,9,10-perylene tetracarboxy diimide (3) was prepared by reacting N,N'-dipropyl-1,7-dibromo-3,4,9,10- perylene tetracarboxy diimide (1) with calix[4]azacrown-5-crown-5. Also the alternating copolymer (4) with similar repeating unit was prepared reacting by calix[4]bisazacrown-5 with 1. Metal ion binding by 3 and 4 leads to a blue-shift of absorption band and emission spectra. When ionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions, polymeric ionophores displayed large fluorescence decreasing effects with K+, Ag+ and Ba2+, which was rationalized by photo-induced charge transfer (PCT).

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.85-96
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• 1994

In this study, 24 curved resin blocks were prepared by one of the following four methods: 1) Conventional technique using K-flexo files 2) Step-back technique using K-flexo files 3) Crown-down technique using K-flexo files 4) Canal Master instrumentation using Canal Master Resin blocks were sectioned, photographed, and evaluated the mean centering ratio and the mean area of dentin removed before and after the instrumentation. The results were as follows : I. the mean centering ratio 1. In the level 1 and level 3, there was no significant difference in the mean centering ratio. 2. In the level 2, Step-back technique showed the worst mean centering ratio among the tested groups(p<0.001) and there was no significant difference between the other three groups. 3. In the level 4, Canal Master instrumentation and Step-back technique showed better mean centering ratio than the other two techniques(p<0.001) and there was no significant difference between the two techniques. II. the mean area of dentin removed 1. In the level l and level 3, there was no significant difference in the mean area of dentin removed. 2. In the level 2, Canal Master instrumentation removed less dentin than the other three techniques(P<0.01). 3. In the level 4, Crown-down technique removed less dentin than the other three techniques(P<0.05).

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.431-436
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• 2015

PURPOSE. The aim of this study was to evaluate occlusal contacts generated by 3 different biogeneric design modes (individual (BI), copy (BC), reference (BR)) of CEREC software and to assess the designs subjectively. MATERIALS AND METHODS. Ten pairs of maxillary and mandibular casts were obtained from full dentate individuals. Gypsum cast contacts were quantified with articulating paper and digital impressions were taken. Then, all ceramic crown preparation was performed on the left first molar teeth and digital impressions of prepared teeth were made. BI, BC, and BR crowns were designed. Occlusal images of designs including occlusal contacts were superimposed on the gypsum cast images and corresponding contacts were determined. Three designs were evaluated by the students. RESULTS. The results of the study revealed that there was significant difference among the number of contacts of gypsum cast and digital models (P<.05). The comparison of the percentage of virtual contacts of three crown designs which were identical to the contacts of original gypsum cast revealed that BI and BR designs showed significantly higher percentages of identical contacts compared with BC design (P<.05). Subjective assessment revealed that students generally found BI designs and BR designs natural regarding naturalness of fissure morphology and cusp shape and cusp tip position. For general occlusal morphology, student groups generally found BI design "too strong" or "perfect", BC design "too weak", and BR design "perfect". CONCLUSION. On a prepared tooth, three different biogeneric design modes of a CAD/CAM software reveals different crown designs regarding occlusal contacts and morphology.

• 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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• 제49권1호
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• pp.22-28
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• 2011

연구 목적: 지르코니아 보철물을 위한 치아 형성이 실제 임상에서 어떻게 이루어지는지에 대해 조사하고 향후 치아 형성에 대한 교육 자료 및 추가 연구의 기초 자료로 활용하고자 한다. 연구 재료 및 방법: 지르코니아 치관 제작을 위해 milling center에 보내진 모형을 조사하여 Lava CAD/CAM System으로 스캔 한 후 'ImageJ' 프로그램 상에서 측정하여, 이를 비교 분석하였다. 각 치아마다 근원심면과 협설면에서의 축면 경사각을 측정하였다. 또한, 견치를 제외한 전치에서 절단연 0.4 mm 하방 부위의 bucco-lingual diameter 측정하였다. 결과 및 결론: 실험군 내에서 지르코니아 전부도재관을 위한 지대치의 축면 경사각은 $18.67^{\circ}$로 문헌에서 추천하는 각도 보다 크게 나타났다. 지르코니아 완전도재관의 지대치 형성 시 축면 경사각은 협설과 근원심면, 악궁 내 위치에 따라 차이가 있었다. Peak 0.4의 평균값은 1.18 mm로 밀링버의 최소직경을 고려한 요구조건인 0.8 mm 보다 큰 값으로 나타났다. 그러나 선각 부위 rounding 에 관한 추가적인 연구가 필요할 것으로 생각된다.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.79-84
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• 2018

PURPOSE. All-ceramic restorations required extensive tooth preparation. The purpose of this in vitro study was to investigate a minimally invasive preparation and thickness of monolithic zirconia crowns, which would provide sufficient mechanical endurance and strength. MATERIALS AND METHODS. Crowns with thickness of 0.2 mm (group 0.2, n=32) or of 0.5 mm (group 0.5, n=32) were milled from zirconia and fixed with resin-based adhesives (groups 0.2A, 0.5A) or zinc phosphate cements (groups 0.2C, 0.5C). Half of the samples in each subgroup (n=8) underwent thermal cycling and mechanical loading (TCML)(TC: $5^{\circ}C$ and $55^{\circ}C$, $2{\times}3,000cycles$, 2 min/cycle; ML: 50 N, $1.2{\times}10^6cycles$), while the other samples were stored in water ($37^{\circ}C/24h$). Survival rates were compared (Kaplan-Maier). The specimens surviving TCML were loaded to fracture and the maximal fracture force was determined (ANOVA; Bonferroni; ${\alpha}=.05$). The fracture mode was analyzed. RESULTS. In both 0.5 groups, all crowns survived TCML, and the comparison of fracture strength among crowns with and without TCML showed no significant difference (P=.628). Four crowns in group 0.2A and all of the crowns in group 0.2C failed during TCML. The fracture strength after 24 hours of the cemented 0.2 mm-thick crowns was significantly lower than that of adhesive bonded crowns. All cemented crowns provided fracture in the crown, while about 80% of the adhesively bonded crowns fractured through crown and die. CONCLUSION. 0.5 mm thick monolithic crowns possessed sufficient strength to endure physiologic performance, regardless of the type of cementation. Fracture strength of the 0.2 mm cemented crowns was too low for clinical application.

• 대한치과보철학회지
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• 제39권3호
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• pp.260-272
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• 2001

All-ceramic restorations have had a more limited life expectancy than metal ceramic restorations because of their low strength. Their relatively lower strength and resistance to fracture have restricted the use of all-ceramic crowns to anterior applications where occlusal loads are lower. But there has been increasing interest in all-ceramic restorations because patients are primarily concerned with improved esthetics. Many efforts have been made to in prove the mechanical properties of dental ceramics. This study was designed to elucidate the influence of the luting agent on the strength of the Empress 2 crown (staining technique) cemented on human teeth. Seventy extracted human permanent molar teeth were chosen. Teeth were prepared for Empress 2 crowns with milling machine on a surveyor. A dental bur was placed in the mandrel that was positioned so that the long axis of the bur was perpendicular to the surveyor base. Dimensions of the Empress 2 crown preparation were $6^{\circ}$ taper on each side, $1.5{\pm}0.1mm$ shoulder margin, and 4mm crown height. The luting cements used in this study were as follow: 1. Uncemented 2. Zinc phosphate cements (Confi-Dental) 3. Conventional glass ionomer cement : Fuji 1 (GC) 4. Resin-modified glass ionomer cements : Fuji plus (GC) 5. Adhesive cements : Panavia F (Kuralay), Variolink II (Vivadent), Choice (Bisco). Fracture test using Instron. The crowns were loaded in compressive force to evaluate the effect of these cements on the breaking strength of these all-ceramic crowns. A steel ball with a diameter of 4mm was placed on the occlusal surface and load was applied to the steel ball by a cylindrical bolt with a crosshead speed of 0.5mm per minute until fracture occurred. The fractured surface was examined using Scanning Electron Microscopic Image (SEM) to discover the correlation between fracture strength and bonding capacity. Within the limitation of this in vitro study design, the results were as follows : 1. fomentations significantly increased the fracture resistance of Empress ceramic crowns compared to control. Uncemented (206.9 N): ZPC (812.9 N): Fuji 1 (879.5 N): Fuji Plus (937.7 N): Choice (1105.4 N): Variolink II (1221.1 N): Panavia F (1445.2 N). 2. Resin luting agent, treated by a silane bond enhancing agents, yielded a significant increase in fracture resistance. In some of the Panavia F group, a fracture extended into dentin. 3. According to SEM images of fractured Empress crowns, the stronger the bond at both interfaces(crown and die), the more fracture strength was acquired.

• 대한치과보철학회지
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• 제57권1호
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• pp.18-23
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• 2019

구순구개열의 존재로 인한 음식물 비강이동, 상악 열성장에 의한 교차교합, 발음, 심미 문제를 해결하기 위해서 상악 구개열 근처 잔존치를 이중관으로 수복하고 구치부위는 구강형성(mouth preparation)을 이용한 고리 유지형 국소의치를 연합하여 사용하였다. 구개열로 인한 점막 지지의 소실을 이중관으로 보충해 줄 수 있고, 지대치의 발치시 수리가 쉬운 장점도 있다. 본 증례는 상악에 몇 개의 남은 치아와 구순구개열을 가진 55세 여자 환자에서 이중관과 고리 유지형 국소의치를 동시에 사용하여 구강비강 결손을 수복한 경우로 이중관과 고리 유지형 국소의치를 연합하여 사용하였다. 그 결과 구순구개열 환자에서의 구강비강연결을 차단할 수 있고, 교차교합을 용이하게 수정할 수 있었다. 또한 이중관 지대치의 이용과 구치부의 고리 유지형 국소의치를 이용하여 환자의 심미와 발음을 개선할 수 있었다.

• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.354-362
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• 2016

PURPOSE. The trueness and precision of acquired images of intraoral digital scanners could be influenced by restoration type, preparation outline form, scanning technology and the application of power. The aim of this study is to perform the comparative evaluation of the 3-dimensional reproducibility of intraoral scanners (IOSs). MATERIALS AND METHODS. The phantom containing five prepared teeth was scanned by the reference scanner (Dental Wings) and 5 test IOSs (E4D dentist, Fastscan, iTero, Trios and Zfx Intrascan). The acquired images of the scanner groups were compared with the image from the reference scanner (trueness) and within each scanner groups (precision). Statistical analysis was performed using independent two-samples t-test and analysis of variance (${\alpha}=.05$). RESULTS. The average deviations of trueness and precision of Fastscan, iTero and Trios were significantly lower than the other scanners. According to the restoration type, significantly higher trueness was observed in crown and inlay than in bridge. However, no significant difference was observed among four sites of preparation outline form. If compared by the characteristics of IOS, high trueness was observed in the group adopting the active triangulation and using powder. However, there was no significant difference between the still image acquisition and video acquisition groups. CONCLUSION. Except for two intraoral scanners, Fastscan, iTero and Trios displayed comparable levels of trueness and precision values in tested phantom model. Difference in trueness was observed depending on the restoration type, the preparation outline form and characteristics of IOS, which should be taken into consideration when the intraoral scanning data are utilized.

• The Journal of Advanced Prosthodontics
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• 제7권3호
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• pp.183-190
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• 2015

PURPOSE. This study evaluated the fracture load of customized zirconia abutments with titanium insert according to preparation depths, with or without 5-year artificial aging. MATERIALS AND METHODS. Thirty-six identical lithium disilicate crowns (IPS e.max press) were fabricated to replace a maxillary right central incisor and cemented to the customized zirconia abutment with titanium insert on a $4.5{\times}10$ mm titanium fixture. Abutments were fabricated with 3 preparation depths (0.5 mm, 0.7 mm, and 0.9 mm). Half of the samples were then processed using thermocycling (temperature: $5-55^{\circ}C$, dwelling time: 120s) and chewing simulation (1,200,000 cycles, 49 N load). All specimens were classified into 6 groups depending on the preparation depth and artificial aging (non-artificial aging groups: N5, N7, N9; artificial aging groups: A5, A7, A9). Static load was applied at 135 degrees to the implant axis in a universal testing machine. Statistical analyses of the results were performed using 1-way ANOVA, 2-way ANOVA, independent t-test and multiple linear regression. RESULTS. The fracture loads were $539.28{\pm}63.11$ N (N5), $406.56{\pm}28.94$ N (N7), $366.66{\pm}30.19$ N (N9), $392.61{\pm}50.57$ N (A5), $317.94{\pm}30.05$ N (A7), and $292.74{\pm}37.15$ N (A9). The fracture load of group N5 was significantly higher than those of group N7 and N9 (P<.017). Consequently, the fracture load of group A5 was also significantly higher than those of group A7 and A9 (P<.05). After artificial aging, the fracture load was significantly decreased in all groups with various preparation depths (P<.05). CONCLUSION. The fracture load of a single anterior implant restored with lithium disilicate crown on zirconia abutment with titanium insert differed depending on the preparation depths. After 5-year artificial aging, the fracture loads of all preparation groups decreased significantly.