• The Journal of Advanced Prosthodontics
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• 제3권2호
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• pp.57-62
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• 2011

MATERIALS AND METHODS. Ceramics have a long history in fixed prosthodontics for achieving optimal esthetics and various materials have been used to improve ceramic core strength. However, there is a lack of information on how color is affected by fabrication procedure. The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of zirconium oxide all-ceramic system (LavaTM) fabricated using CAD/CAM technology. MATERIALS AND METHODS. Thirty disc-shaped cores, 12 mm in diameter with a 1 mm thickness were fabricated from zirconium oxide based all ceramic systems ($Lava^{TM}$, 3M ESPE, St Paul, MN, USA) and divided into three groups (n = 10) according to veneering with dentin ceramic thicknesses: as 0.5, 1, or 1.5 mm. Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade, VITA Zahnfabrik, Bad $S{\ddot{a}}ckingen$, Germany) and data were expressed in CIELAB system coordinates. A repeated measures ANOVA and Bonferroni post hoc test were used to analyze the data (n = 10, ${\alpha}=.05$). RESULTS. $L^{\ast}a^{\ast}b^{\ast}$ values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (P<.001) and ceramic thickness (0.5, 1, or 1.5 mm) (P<.001). Significant interactions were present in $L^{\ast}a^{\ast}b^{\ast}$ values between the number of firings and ceramic thickness (P<.001). An increase in number of firings resulted in significant increase in $L^{\ast}$ values for both 0.5 mm and 1.5 mm thicknesses (P<.01, P=.013); however it decreased for 1 mm thickness (P<.01). The $a^{\ast}$ values increased for 1 mm and 1.5 mm thicknesses (P<.01), while it decreased for 0.5 mm specimens. The $b^{\ast}$ values increased significantly for all thicknesses (P<.01, P=.022). As the dentin ceramic thickness increased, significant reductions in $L^{\ast}$ values (P<.01) were recorded. There were significant increases in both $a^{\ast}$ and $b^{\ast}$ values (P<.01) as the dentin ceramic thickness increased. CONCLUSION. The number of firings and dentin ceramic thickness have a definite effect on the final color of all ceramic system tested. The mean ${\Delta}E$ value increased as the dentin ceramic thicknesses increased for zirconium-oxide based all ceramic specimens tested. However, the mean ${\Delta}E$ values were less than 3.7${\Delta}E$ units which is rated as a match in the oral environment.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.485-493
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• 2013

PURPOSE. To evaluate the effects of surface treatments on shear bond strength (SBS) between microwave and conventionally sintered zirconia core/veneers. MATERIALS AND METHODS. 96 disc shaped Noritake Alliance zirconia specimens were fabricated using YenaDent CAM unit and were divided in 2 groups with respect to microwave or conventional methods (n=48/group). Surface roughness (Ra) evaluation was made with a profilometer on randomly selected microwave (n=10) and conventionally sintered (n=10) cores. Specimens were then assessed into 4 subgroups according to surface treatments applied (n=12/group). Groups for microwave (M) and conventionally (C) sintered core specimens were as follows; $M_C$,$C_C$: untreated (control group), $M_1,C_1:Al_2O_3$ sandblasting, $M_2,C_2$:liner, $M_3,C_3:Al_2O_3$ sandblasting followed by liner. Veneer ceramic was fired on zirconia cores and specimens were thermocycled (6000 cycles between $5^{\circ}-55^{\circ}C$). All specimens were subjected to SBS test using a universal testing machine at 0.5 mm/min, failure were evaluated under an optical microscope. Data were statistically analyzed using Shapiro Wilk, Levene, Post-hoc Tukey HSD and Student's t tests, Two-Way-Variance- Analysis and One-Way-Variance-Analysis (${\alpha}$=.05). RESULTS. Conventionally sintered specimens ($1.06{\pm}0.32{\mu}m$) showed rougher surfaces compared to microwave sintered ones ($0.76{\pm}0.32{\mu}m$)(P=.046), however, no correlation was found between SBS and surface roughness (r=-0.109, P=.658). The statistical comparison of the shear bond strengths of $C_3$ and $C_1$ group (P=.015); $C_C$ and $M_C$ group (P=.004) and $C_3$ and $M_3$ group presented statistically higher (P=.005) values. While adhesive failure was not seen in any of the groups, cohesive and combined patterns were seen in all groups. CONCLUSION. Based on the results of this in-vitro study, $Al_2O_{3-}$ sandblasting followed by liner application on conventionally sintered zirconia cores may be preferred to enhance bond strength.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.479-484
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• 2013

PURPOSE. The aim of this study was to evaluate the effects of additional acid etching and curing mechanism (light-curing or self-curing) of a composite resin on the dentin bond strength and compatibility of one-step self-etching adhesives. MATERIALS AND METHODS. Sixteen human permanent molars were randomly divided into eight groups according to the adhesives used (All-Bond Universal: ABU, Clearfil S3 Bond: CS3), additional acid etching (additional acid etching performed: EO, no additional acid etching performed: EX), and composite resins (Filtek Z-250: Z250, Clearfil FII New Bond: CFNB). Group 1: ABU-EO-Z250, Group 2: ABU-EO-CFNB, Group 3: ABU-EX-Z250, Group 4: ABU-EX-CFNB, Group 5: CS3-EO-Z250, Group 6: CS3-EO-CFNB, Group 7: CS3-EX-Z250, Group 8: CS3-EX-CFNB. After bonding procedures, composite resins were built up on dentin surfaces. After 24-hour water storage, the teeth were sectioned to make 10 specimens for each group. The microtensile bond strength test was performed using a microtensile testing machine. The failure mode of the fractured specimens was examined by means of an optical microscope at ${\times}20$ magnification. The data was analyzed using a one-way ANOVA and Scheffe's post-hoc test (${\alpha}$=.05). RESULTS. Additional etching groups showed significantly higher values than the no additional etching group when using All-Bond Universal. The light-cured composite resin groups showed significantly higher values than the self-cured composite resin groups in the Clearfil S3 Bond. CONCLUSION. The additional acid etching is beneficial for the dentin bond strength when using low acidic one-step self-etch adhesives, and low acidic one-step self-etch adhesives are compatible with self-cured composite resin. The acidity of the one-step self-etch adhesives is an influencing factor in terms of the dentin bonding strength and incompatibility with a self-cured composite resin.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.471-478
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• 2013

PURPOSE. The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS. Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring $4{\times}2{\times}2$ mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS. The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness ($48.16{\pm}3.02$ HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness ($27.40{\pm}3.98$ HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 ${\AA}$). CONCLUSION. After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

• 대한치과보철학회지
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• 제55권4호
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• pp.389-393
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• 2017

목적: 본 연구의 목적은 탄성력이 높게 개발된 레진의 굽힘 강도를 평가하고, resin wire splint (RWS)와 유연성을 비교 평가하는 것이다. 재료 및 방법: 세가지 레진 G-aenial flo (GA, GC), Superbond (SB, Sun medical), G-fix (GF, GC)의 세 점 굽힘 강도는 ISO4049/2000에 따라 진행하였다. GA, SB, GF를 이용한 세개의 RS군과 GA와 교정용 016" SS wire를 이용한 RWS군간의 치아 동요도 비교는 영구치 모형을 이용하였다. 상악좌측중절치에 3도의 동요를 부여하고, 치아의 수평적인 동요도를 splint 전후에 각 3회씩 periotest vale로 평가하였다. Splint 전후 periotest value는 splinting 효과로 환산하여 평가하였다. 통계적인 평가는 one-way ANOVA와 turkey HDS test를 이용하였다(${\alpha}=.05$). 결과: SB와 GF가 GA에 비해 낮은 굴곡강도를 보였으나, 세가지 RS군은 RWS에 비해 높은 splinting 효과를 나타내었다 (P < .05). 결론: 제한된 본 연구에서 사용된 재료와 상관없이 RS는 RWS에 비해 높은 견고성을 보였으며, 이는 탈구치아 치료를 위한 flexible splint에 부적합한 것으로 보인다.

• 대한치과보철학회지
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• 제58권4호
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• pp.282-289
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• 2020

목적:본 연구의 목표는 다른 유형의 엔도크라운(endocrown) 와동 형태를 세 가지 다른 구강스캐너로 디지털 인상을 채득하였을 때의 정확성을 평가하는 것이다. 재료 및 방법: 두 개의 인체 하악 대구치를 협측벽이 있는 것(Class 2)과 협측벽이 없는(Class 3), 두 가지 엔도크라운 지대주 디자인으로 치아형성 하였다. 와동 디자인 2종을 레퍼런스로 탁상용 스캐너(E3, 3shape)와 세 개의 다른 구강스캐너, Trios 3 (3shape, TRI group), Cerec Omnicam (Dentsply Sirona, CER group), i500 (Medit Corp., I5 group)로 스캔하였다. 표준 테셀레이션 언어(.stl) 데이터 세트를 얻어, 계측 소프트웨어에서 불러들였다. 각 구강스캐너로 획득한 반복된 스캔 데이터 사이의 편차에 기초하여 정밀도(precision)를 평가하였다. 기준 데이터와 반복하여 얻은 구강스캔 사이의 편차로서 진도(trueness)를 평가 하였다. 상호작용을 탐지하기 위해 데이터는 일변량 분산분석(ANOVA)을 사용하여 통계적으로 분석하였고, 실험군의 비교 분석을 위해 데이터는 .05의 유의 수준에서 일원 분산분석 및 사후 Tukey 테스트로 분석하였다. 결과: I5 군의 두 와동 형태에 대한 편차값은 진도의 측면에서 다른 구강스캐너 군에 비해 낮았다. 두 와동 디자인 모두에서 TRI 군은 다른 구강스캐너군 보다 우수한 정밀도를 보였다. 결론: 구강스캐너의 다양한 기술과 다양한 엔도크라운 치아형성 디자인이 디지털 스캔의 정확도에 영향을 미쳤다.

• 한국조리학회지
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• 제23권2호
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• pp.11-22
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• 2017

이 연구는 포지셔닝 전략에 관한 연구로서 프랜차이즈 분식점 브랜드의 경쟁관계를 분석하고, 고객의 욕구를 충족시켜주는 선택속성이 무엇인지 파악하여 효율적인 포지셔닝 전략을 수립함으로 발전적인 마케팅 방향을 제시하였다. 요인분석을 통하여 고객들이 인지하는 프랜차이즈 분식점들의 선택속성은 총 25의 문항들은 총 3개의 요인으로(음식의 품질, 직원들의 서비스, 물리적 환경)으로 범주화 되었다. 이용동기에 집단 간 유의미한 차이가 있는지를 알아보기 위하여 일원배치분석(ANOVA)를 실시하여 Duncan을 통하여 사후분석하였고, 다차원척도법(MDS)을 통하여 브랜드 유사성, 선택속성과 브랜드 선호도를 검증하였다. 아딸은 음식, 서비스, 물리적 환경 속성에서 평균보다 높은 점수를 받았으며, 봉구스 밥버거는 서비스와 물리적 환경, 고봉민 김밥은 음식과 물리적 환경속성이 평균보다 높았다. 김밥천국은 음식, 서비스, 물리적 환경의 세 요인 모두에서 평균보다 낮게 나타났다. 본 연구의 결과는 5개의 프랜차이즈 분식점에 대한 유용한 경쟁관계를 나타내는 포지셔닝 맵과 실용적인 제안을 제공하였다.

• 한국보육지원학회지
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• 제5권2호
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• pp.1-20
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• 2009

본 연구에서는 예비유아교사의 창의적 인성과 교사효능감의 상관관계에 대해 알아보고자 하였다. 연구대상은 보육실습과 교육실습의 경험이 있는 경기지역에 소재한 S대학, Y대학 유아교육과 3학년 학생 165명이었다. 측정도구로는 하주현의 창의적 인성검사와 김순남에 의해 수정된 TEBI(Teaching Eefficacy Belief Instrument)교사효능감 검사를 사용하였다. 수집한 자료는 일원변량분석, schaffer 사후검증, 적률상관계수, 중다회귀분석을 이용하여 분석하였다. 본 연구의 결과는 다음과 같다. 첫째, 예비유아교사의 배경변인(성적, 연령, 임원활동)에 따른 창의적 인성의 차이는 유의하지 않았다. 둘째, 예비유아교사의 배경변인에 따른 교사효능감의 차이에서 '연령'은 교사효능감과 정적인 상관관계를 보였으며 특히 개인 교사효능감에 유의한 차이가 있었다. 셋째, 창의적 인성 점수가 높은 예비유아교사들이 교사효능감도 대체로 높았으며 특히 개인 교사효능감에서 더욱 유의미한 상관관계를 나타냈다. 예비유아교사의 교사효능감을 예언해주는 창의적 인성 요인은 자기 확신, 상상, 개방성'인 것으로 나타났다. 연구결과를 토대로, 예비유아교사의 창의적 인성과 일반 교사효능감의 관계를 인식하고 이를 촉진하는 교육과정 운영방안에 대해 논의하였다.

• 구강회복응용과학지
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• 제19권4호
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• pp.269-279
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• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.

• 대한치과보철학회지
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• 제49권1호
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• pp.49-56
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• 2011

연구 목적: 최근 지르코니아가 전부도재관의 코어로 많이 사용되고 있다. 지르코니아와 레진 시멘트의 결합 강도를 높이기 위한 기계적, 화학적인 표면 처리 방법들이 연구되고 있다. 이 연구에서 여러 표면 처리 방법에 따른 지르코니아와 레진 시멘트의 전단결합강도를 알아보고자 한다. 연구 재료 및 방법: 80개의 지르코니아 (Lava, 3M ESPE, St. Paul, MN, USA) 시편과 80개의 지르코니아/알루미나 복합체 (Zirace, Acucera Co Inc, Korea) 시편을 디스크형태로 제작하여 에폭시레진에 매립하였다. 이들을 각각 4개의 군으로 나누어 $50\;{\mu}m$ $Al_2O_3$ sandblasting, $110\;{\mu}m$ $Al_2O_3$ sandblasting, $50\;{\mu}m$ $Al_2O_3$ sandblasting과 프라이머 (Z-PRIME Plus, Bisco Inc, Schaumburg, IL, USA) 사용, $110\;{\mu}m$ $Al_2O_3$ sandblasting과 프라이머 (Z-PRIME Plus) 사용 군으로 나누었다. 표면 처리한 지르코니아 표면에 2가지 레진 시멘 (Calibra, Panavia F)으로 접착하였다. 그 후 증류수 ($37^{\circ}C$)에 24시간 보관 후 전단 결합 강도 실험을 시행하였고, SEM을 사용하여 표면 처리한 표면과 전단강도 실험 후 파절양상을 관찰하였다. 결과: ANOVA분석에 따르면, 두 가지 종류의 시편 모두에서, 프라이머 (Z-PRIME Plus)를 사용하여 표면 처리한 군들이 전단 결합 강도가 높았다 (P < .05). 결론: 기계적 결합 강도와 함께 새로운 프라이머를 사용하는 것이 지르코니아와 레진 시멘트의 접착 강도를 증가시킨다.