• 한국정밀공학회지
• /
• 제28권4호
• /
• pp.474-481
• /
• 2011

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the finite element stress analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia crown were prepared. Each model contained cortical bone, trabecular bone, periodontal ligament, 4mm apical root canal filling, and post-and-core. A 50N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$ angle to the long axis of the tooth. And three parallel type post (zirconia, glass fiber and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. For the Result of the research, the model applied glass fiber to post material has lowest von Mises stress and it is suitable for material of post core systems.

• Restorative Dentistry and Endodontics
• /
• 제25권3호
• /
• pp.482-486
• /
• 2000

The purpose of the present study was first, to evaluate the relationship between composite surface conversion and surface discoloration, second, to know if there was difference in surface discoloration between celluloid-strip-finished composite surface and polished surface. In addition, the discoloration of composite surface was also evaluated with visual inspection or digital camera with high resolution monitor, Z100, Tetric Ceram, Spectrum, and Aelitfil were used. The composite surfaces were celluloid-strip finished (group 1), polished (group 2), celluloid-strip finished under nitrogen gas purging (group 3) or only light cured without finishing or polishing under nitrogen gas purging (group 4). The microhardness of each samples were also measured in each group. The samples of each group were also divided into 4 subgroup whether they were immediately placed in disclosing solution (0.2% Elythrosin, pH 7.0) (subgroup1), 1 day after light curing(subgroup 2), 3day after light curing(subgroup 3) or 7 day after light curing(subgroup 4). The computer controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$, $b^*$). The amounts of color difference were compared. The results were as follows; 1. There was no difference in discoloration between celluloid strip finished composite surface and polished surface. 2. The samples discolored more when they were placed in disclosing solution immediately after polymerization than other groups. 3. When the samples were light cured under nitrogen gas purging and without polishing process, they discolored more than other groups even though they showed higher micro hardness. 4. With visual inspection or digital camera, only a limited information was available in detecting composite surface discoloration.

• Restorative Dentistry and Endodontics
• /
• 제29권4호
• /
• pp.353-364
• /
• 2004

The purpose of this study was to compare and to evaluate the combination use of 5 kinds of dentin adhesive systems and 5 kinds of composite resins using micro-shear bond test. Five adhesive systems (Prime & Bond NT (PBN). Onecoat bond (OC), Excite (EX), Syntac (SY), Clearfil SE bond (CS)) and five composite resins (Spectrum (SP), Synergy Compact (SC), Tetric Ceram (TC), Clearfil AP-X (CA), Z100 (Z1)) were used for this study ($5{\;}{\times}{\;}5{\;}={\;}25group$, n =14/group). The slices of horizontally sectioned human tooth were bonded with each bonding system and each composite resin, and tested by a micro-shear bond strength test. These results were analyzed statistically. The mean micro-shear bond strength of dentin adhesive systems were in order of CS (22.642 MPa), SY (18.368 MPa), EX (14.599 MPa). OC (13.702 MPa). PBN (12.762 MPa). The mean bond strength of self-etching primer system group (CS, SY) in dentin was higher than that of self-priming adhesive system groups (PBN, EX, OC) significantly (P<0.05). The mean bond strength of composite resins was in order of SP (19.008 MPa), CA (17.532 MPa). SC (15.787 MPa), TC (15.068 MPa). Z1 (14.678 MPa). Micro-shear bond strength of SP was stronger than those of other composite resins significantly (P < 0.05). And those of TC and Z1 were weaker than other composite resins significantly (P < 0.05). No difference was found in micro-shear bond strength of composite resin in self-etching primer adhesive system groups (CS, SY) statistically. However, there was significant difference of micro-shear bond strength of composite resin groups in self-priming adhesive systems group (PBN, EX, OC). The combination of composite resin and dentin adhesive system recommended by manufacturer did not represent positive correlation. It didn't seem to be a significant factor.

• Restorative Dentistry and Endodontics
• /
• 제25권1호
• /
• pp.56-62
• /
• 2000

The purpose of this study was to assess the effects of restorative materials on the marginal leakage of wedge-shaped class V cavity. The study was performed in vitro in 25 defect-free permanent, extracted teeth. Wedge-shaped class V cavities were prepared and then the teeth were randomly selected and restored according to the following. Group A : restoration with Tetric Ceram(composite resin) Group B : restoration with Tetric flow(flowable resin) Group C : restoration with Compoglass after acid etching(compomer) Group D : restoration with Compoglass(compomer) Group E : restoration with Fuji II LC improved(resin-modified GIC) After thermocycling, the specimens were immersed in 5% basic fuchsin solution for 6 hours and sectioned longitudinally through the center of the restoration. The degree of marginal leakage was measured as the extent of dye penetration under the stereomicroscope. The data were analysed using one-way ANOVA. When significant differences found, multiple comparisons were made using Duncan's Multiple Range Test. The results were as follows: 1. The occlusal margins of all groups except for Fuji II LC improved showed lesser leakage than gingival margins and there was statistically significant difference(p<0.05). 2. At the occlusal margins, group A, B showed same marginal leakage scores, and others were decreased as group C, D, E in that order. There were statistically significant difference between group A, Band group D, E, group C and group E(p<0.05). 3. At the gingival margins, group B, C showed same marginal leakage scores, and others were decreased as group A, D, E in that order. But there was statistically significant difference between group B, C and group E(p<0.05). 4. In the Compoglass restoration, acid-etching technique was beneficial for marginal sealing ability at all of margins. But there was no statistically significant difference (p>0.05). In the restorations for wedge-shaped class V cavities, resin restoration with acid etching technique is recommended.

• 한국세라믹학회지
• /
• 제34권1호
• /
• pp.88-94
• /
• 1997

플라즈마 용사법(plasma spray method)으로 제작된 상용 가스 터빈 연소기의 finned segment의 열차폐용 코팅계, ZrO2-8wt%Y2O3 top coat/Ni-26Cr-5Al-0.5Y bond coat/Hastelloy X superalloy 기판에서 NiCrAlY bond coat의 산화 거동과 열피로 파괴에 대하여 조사하였다. 생성된 bond coat의 주산화물은 NiO, CrO2, Al2O3였다. ZrO2/bond coat계면에서 생성된 산화물의 분포는 고온에서의 사용 전에 이 계면 아래에 얇은 층의 Al2O3가없는 곳에서는 NiO 산화층 및에 Cr2O3와 Al2O3가 혼합된 형태를 나타내었다. 열피로에 의해 박리된 시편의 파면을 관찰한 결과, 파괴는 주로 ZrO2/산화층 계면보다 세라믹층내로 약간 치우쳐서 일어나지만, 산화층 내에서도 약간 일어남을 알 수 있었다.

• 대한치과보철학회지
• /
• 제44권3호
• /
• pp.333-342
• /
• 2006

Statement of problem. Although many studies have been carried out to investigate the correlation between the degree of conversion and the flexural strength of composite resins, there is minimal information in the literature attempting to compare degree of conversion, flexural strength and their correlation between restorative composite resins and flowable composite resins. Purpose. The purposes of this study were to measure the degree of conversion and flexural strength of composite resins with different rheological behavior and to correlate the two properties. Materials and methods. Four restorative (Vit-1-escence, Z-250, Tetric ceram, Esthet-X) and four flowable (Aeliteflo, Admiraflow, Permaflo, Revolution) light-curing composite resins were investigated. The degree of conversion(DC) was analyzed with Fourier transfer infra-red spectroscopy(FTIR) spectrum by a potassium bromide(KBr) pellet transmission method. The spectrum of the unpolymerized specimen had been measured before the specimen was irradiated for 60s with a visible light curing unit. The Poiymerized specimen was scanned for its in spectrum. The flexural strength(FS) was measured with 3-point bending test according to ISO 4049 after storage in water at $37^{\circ}C$ for 24 hours. The data were statistically analyzed by an independent sample t-test and one-way ANOVA at the significance level of 0.05. The dependence of flexural strength on the degree of conversion was also analyzed by regression analysis. Results. Mean DC and FS values ranged from 43% to 61% and from 84.7MPa to 156.7MPa respectively. DC values of the flowable composite resins were significantly higher than those of restorative composite resins (P < 0.05). The FS values of restorative composite resins were greater than those of flowable composite resins. No statistically significant correlation was observed between the DC and the FS tested in any of the composites. The dependence of FS on DC in restorative or flowable composite resins was not significant. Conclusion. It can be concluded that radical polymerization of the organic matrix is not a major factor in determining flexural strength of the commercially available composite resins.

• Restorative Dentistry and Endodontics
• /
• 제25권1호
• /
• pp.63-70
• /
• 2000

The properties of ideal retrograde filling materials include the ability to seal the root canal system in three dimensions and well tolerated by periradicular tissues. Biocompatibility testing has been done mainly with cytotoxicity tests using cell culture. Little attention has been paid to the potential adverse influence on the inflammatory and immune reaction in the periapical tissue. The purpose of this study was to investigate the effects of retrograde filling materials on human mononuclear cells in vitro. Freshly mixed and set specimens from six materials (Z100, Tetric Ceram, Fuji II, Fuji II LC, F2000, Compoglass Flow, and ZOE) were eluated with cell culture medium for 24 hours. Cytotoxic effects of these extracts were evaluated by determining cell viability and enzyme activity using MTT and lactate dehydrogenase (LD). The production of inflammatoy bone resorptive cytokine, TNF-${\alpha}$ was measured from human peripheral blood mononuclear cells (PBMC) exposed to the extracts by means of Endogen Human TNF-${\alpha}$ ELISA kit (Wobrun, MA, U.S.A.). Eluates and diluted (1 : 10) eluates with cell culture medium from freshly mixed Fuji IT had cytotoxic effects on mononuclear cells using MTT and LD. However, eluates from set Fuji II were not cytotoxic. Eluates form set ZOE exhibited cytotoxicity with LD test. TNF-${\alpha}$ levels were high in eluates from freshly mixed Fuji II and Z100. Diluted eluates from freshly mixed Z100 and F2000 stimulated the production of TNF-${\alpha}$. However, there were no significant difference in TNF-${\alpha}$ levels compared to controls. These results indicate that some materials could possibly stimulate bone resorption in the periapical tissue by means of the production of bone resorptive cytokine.

• 한국전산유체공학회지
• /
• 제18권3호
• /
• pp.67-71
• /
• 2013

Recently, the rapid development of the semiconductor industry induces the prompt technical progress in the area of device integration and the application of large diameter wafers for the price competitiveness. As a result of the usage of large wafers in the semiconductor industry, the silicon carbide components which have layers of silicon carbide on graphite or RBSC substrates is getting widely used due to the advantages of SiC such as high hardness and strength, chemical and ionic resistant to all the environments superior than other ceramic materials. For the uniform and homogeneous deposition of silicon carbide on these huge components, it needs to know about the gas flow in the CVD reactor, not only for the delicate adjustment of the process variables but more essentially for the cost reduction for the shape change of specimens and their holders on the stage of reactor. In this research, the CFD simulation is challenged for the prediction of the inner distribution of the gas velocity. Chemical reaction simulation is used to predict the distribution of concentration of the reacting gas with the rotating velocity of the stage. With the increase of the rotating speed, more uniform distribution of the reacting gas on the surface of the stage was obtained.

• 대한소아치과학회지
• /
• 제35권3호
• /
• pp.418-426
• /
• 2008

본 연구에서는 구강 환경과 유사한 조건에서 불소방출성을 보이는 콤포짓트 레진계 수복재의 내구성과 불소방출성을 조사하기 위해 4 종의 콤포머와 1 종의 불소방출성 콤포짓트 레진을 실험재료로 선택하고 $5^{\circ}C$와 $55^{\circ}C$ 수중에서의 열순환 처리 후의 인장강도, 열순환 처리 후 칫솔에 대한 작용력 1.5N으로 100,000회 칫솔질을 시행하였을 때의 표면조도 및 불소치약 칫솔질 후 $37^{\circ}C$ 수중에서의 불소이온 용출 양상을 조사한 결과 다음과 같은 결론을 얻었다. 1. 인장강도는 TC($Tetric^{(R)}$ Ceram)군에서 32.3 MPa, CF(Compoglass F)군에서 16.8 MPa이고, TC군과 DF($Dyract^{(R)}$ flow)군 및 CF군에서 유의한 차이를 보였다(P<0.05). 2. 칫솔질 마모시험 후의 표면조도 Ra는 TC군에서 0.287, FT(F2000)군에서 1.516이고, FT군과 나머지 시험군 사이에 유의한 차이를 보였다(P<0.05). 3. 칫솔질 마모시험 후의 표면에서는 필러의 돌출과 탈락 양상이 관찰되었다. 4. 불소치약 Perio Alpine Herb로 칫솔질 한 후 콤포머는 초기에 높은 용출을 보인 후 시간이 경과하면서 용출량이 감소하는 양상을 보였지만, 불소방출성 콤포짓트 레진의 TC군에서는 초기단계부터 낮으면서도 지속적인 용출을 보였다. 5. 불소치약 Perio Alpine Herb로 칫솔질 한 후 1시간이 경과하였을 때의 불소이온 용출량은 CF군에서 $2.064{\mu}g/cm^2$, TC 군에서 $0.1119{\mu}g/cm^2$이고, CF군의 용출량이 나머지 시험군에 비해 유의하게 높은 값을 보였다(P<0.05).

• Restorative Dentistry and Endodontics
• /
• 제46권3호
• /
• pp.39.1-39.12
• /
• 2021

Objectives: This study analyzed the physical-chemical behavior of 2 bulk fill resin composites (BFCs; Filtek Bulk Fill [FBF], and Tetric-N-Ceram Bulk Fill [TBF]) used in 2- and 4-mm increments and compared them with a conventional resin composite (Filtek Z250). Materials and Methods: Flexural strength and elastic modulus were evaluated by using a 3-point bending test. Knoop hardness was measured at depth areas 0-1, 1-2, 2-3, and 3-4 mm. The translucency parameter was measured using an optical spectrophotometer. Real-time polymerization kinetics was analyzed using Fourier transform infrared spectroscopy. Results: Flexural strength was similar among the materials, while TBF showed lower elastic modulus (Z250: 6.6 ± 1.3, FBF: 6.4 ± 0.9, TBF: 4.3 ± 1.3). The hardness of Z250 was similar only between 0-1 mm and 1-2 mm. Both BFCs had similar hardness until 2-3 mm, and showed significant decreases at 3-4 mm (FBF: 33.45 ± 1.95 at 0-1 mm to 23.19 ± 4.32 at 3-4 mm, TBF: 23.17 ± 2.51 at 0-1 mm to 15.11 ± 1.94 at 3-4 mm). The BFCs showed higher translucency than Z250. The polymerization kinetics of all the materials were similar at 2-mm increments. At 4-mm, only TBF had a similar degree of conversion compared with 2 mm. Conclusions: The BFCs tested had similar performance compared to the conventional composite when used in up to 2-mm increments. When the increment was thicker, the BFCs were properly polymerized only up to 3 mm.