• Restorative Dentistry and Endodontics
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• 제22권2호
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• pp.751-760
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• 1997

Resin-modified glass ionomers were introduced in 1988 to overcome the problems of moisture sensitivity and low early mechanical strengths of the conventional glass ionomers, and to maintain their dinical advantages. The purpose of this study was to evaluate the bi-axial fracture strength of four resinmodified glass-ionomers(Fuji II LC, Vitremer, Dyract, VariGlass), one resin composite material(Z-100), and one conventional glass-ionomer(Fuji II). Three specimens of each material and shade combination were made according to the manufacturers' instructions. Materials were condensed into metal mold with a diameter of 10mm and a thickness of 2.0mm and pressed between two glass plates. Resin-modified glass ionomers were polymerized using a Visilux II light curing unit by irradiating for 60 seconds from both sides, and conventional glass ionomer was cured chemically. After specimens were removed from the molds, surfaces were polished sequentially on wet sandpapers up to No. 600 silicone carbide paper. The specimens were thermocycled for 2,000 cycles between $5^{\circ}C$ and $55^{\circ}C$ distilled water. After thermocycling, bi-axial fracture strengths were measured using a compressive-tensile tester(Zwick 1456 Z020, Germany) with the cross head speed of 0.5mm/minute. The results were as follows: 1. Two factors of the kind and color of materials had a main effect on bi-axial fracture strength (p<0.01), and bi-axial fracture strength was influenced significantly by the kinds of materials (p<0.01). But there was no significant interaction between two variables of the kind and color of materials (p>0.05). 2. Comparing the mechanical properties of the materials, the elastic modulus of Z100 was higher than any other material, and there was no difference in the displacement at fracture among materials. The bi-axial fracture strength of Z100 was significantly higher than any other material, and that of resin-modified glass ionomers was significantly higher than that of conventional glass ionomer (p<0.05). 3. In the same material group, the color of material had little influence on the mechanical properties.

• 대한치과보철학회지
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• 제46권5호
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• pp.511-519
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• 2008

연구목적: 본 연구의 목적은 자가중합 또는 이중중합을 위한 활성제가 포함된 상아질 접착제에서 활성제의 사용 유무가 자가중합 복합레진과 상아질 접착제간의 전단결합강도에 미치는 영향을 평가하는 것이다. 연구 재료 및 방법: 실험을 위하여 우식 및 충전물이 없는 건전한 대구치 50개를 주문제작한 아크릴릭 레진블록에 포매한 후, 모델 트리머로 연마하여 평활한 상아질면을 만든 후, 600grit 실리콘 카바이드 페이퍼로 연마하고 증류수에 보관하였다. 50개의 시편을 10개씩 5개 군으로 나눈 후, 상아질 접착제를 제조사의 지시대로 도포한 후, 플라스틱 주형을 이용하여 자가중합 복합레진 (Luxacore)을 접착시켰다. 상아질 접착제는 One-Step (OS군), Prime&Bond NT, AdheSE를 이용하였는데 Prime&Bond NT와 AdheSE는 단독으로 사용한 군 (PB군, AS군)과 활성제를 같이 사용한 군 (PBA군, ASA군)으로 다시 나누었다. 증류수에 24시간 보관 후, 인스트론 만능시험기를 사용하여 시편에 1 mm/min의 전단속도로 하중을 가하여 시편이 분리되는 최대 하중을 측정한 뒤, 단위 면적 당 결합강도 (MPa)로 환산하여 One-way ANOVA를 이용하여 비교, 분석하고 5% 유의수준에서 Tukey HSD 검정을 이용하여 분석하였다. 결과: 각 군의 전단결합강도의 평균을 보면, OS군이 18.6 MPa로 가장 높았고 그 다음이 PBA군 (10.3 MPa)과 ASA군 (10.2 MPa)이었고, PB군과 AS군이 각각 5.9 MPa, 6.0 MPa로 가장 낮은 전단결합강도를 나타내었다. 결론: 본 실험을 통해 Prime&Bond NT와 AdheSE에서 활성제를 같이 사용한 경우, 활성제를 사용하지 않은 경우보다 전단결합강도가 높아짐을 알 수 있었지만, 활성제가 포함되어 있지 않은 One-Step보다는 낮은 수치였다.

• Restorative Dentistry and Endodontics
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• 제25권4호
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• pp.499-508
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• 2000

본 연구에서는 이종의 디지털 방사선사진술이 수복물의 방사선불투과성 비교에 적절하게 이용될 수 있는지의 여부를 평가하고, 이 기법을 이용하여 수종의 compomer 및 유동성 레진의 방사선불투과도를 측정, 비교하고자 하였다. Aluminum step wedge를 방사선사진촬영 하여 기 존의 transmission densitometer와 CD-Dent (phosphor scanning system) 및 RVG$^{(R)}$ (CCD system) 등 두 종류의 디지털 방사선사진술과의 광학밀도 상관관계를 평가하였고, 두께 2mm, 지름 5mm인 원형의 금속주형을 이용하여 Dyract$^{(R)}$ AP, Compoglass$^{(R)}$ 및 Dyract flow$^{(R)}$ 등 3종의 compomer와 Ultraseal-XT$^{(R)}$ plus$^{TM}$, Revolution$^{TM}$, Aeliteflo$^{TM}$ 및 Tetric-flow$^{(R)}$ 등 4종의 유동성 레진의 시편을 각각 5개씩 제작후 방사선불투과성을 측정하고 비교, 평가하여 다음과 같은 결과를 얻었다. 1. Aluminum step wedge를 사용한 광학밀도 측정곡선을 비교한 바, 통상적인 방사선사진술로 얻은 필름의 상에서 transmission densitometer로 방사선불투과도를 측정 한 곡선과 CD-Dent 및 RVG$^{(R)}$ 등 디지털 방사선사진술로 얻은 상에서 CADIA로 불투과도를 측정한 곡선들 사이에서 각각 매우 높은 역상관관계가 나타났다(${\gamma}$=-0.95, ${\gamma}$=-0.98 ; p<0.05). 2. 모든 수복채 공히 상아질과 유사하거나 높은 방사선불투과도를 나타내었고 (p<0.05), compomer인 Dyract$^{(R)}$ AP와 Compoglass$^{(R)}$, 그리고 유동성 레진인 Tetric-flow$^{(R)}$는 통상적인 방사선사진술 및 2종의 디지털 방사선사진술에서 공히 유동성 레진인 Revolution$^{TM}$과 Aeliteflo$^{TM}$, 그리고 상아질에 비해 유의하게 높은 방사선불투과도를 나타내었다 (p<0.05). 3. Compomer인 Dyract$^{(R)}$ AP와 Compoglass$^{(R)}$, 그리고 유동성 레진인 Tetric-flow$^{(R)}$는 통상적인 방사선사진술 및 CD-Dent 디지털 방사선사진술에서 공히 법랑질에 비해 높은 방사선불투과도를 나타내었고(p<0.05), compomer인 Dyract flow$^{(R)}$는 통상적인 방사선사진술에서만 법랑질에 비해 높은 방사선불투과도를 나타내었다(p<0.05).

• 대한치과보철학회지
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• 제47권2호
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• pp.164-173
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• 2009

연구 목적: 심미적 장점을 지닌 지르코니아 지대주와 금속 지대주 사이에 반복 하중 전, 후의 풀림 회전력을 비교하여 지대주 재질에 따른 나사 안정성에 차이가 있는지를 비교 분석해 보고자 하는 것이다. 연구 재료 및 방법: 실험군은 크게 외측 연결 구조(US II, Osstem Implant, Korea)와 내측 연결 구조(GS II, Osstem Implant, Korea)의 임플란트 시스템을 두 군으로 나누었다. 각각의 군에서 지르코니아 지대주군와 금속 지대주군으로 나누어 실험하였다. 각군당5개씩의 시편을 제작하였다. 임플란트 고정체를 별도 제작된 지그에 고정시킨다. 디지털 토크게이지를 이용하여 30 Ncm의 조임 회전력을 가하고 10분 후 동일 조임 회전력을 한번 더 적용하였다. 다음 각 지대주 나사의 초기 풀림 회전력을 디지털 토크게이지로 측정하였다. 동일 시편을 다시 30 Ncm의 조임 회전력을 가하여 체결한 후, 유압식 동적 재료시험기(Instron, USA)에 임플란트 매식체를 치과용 임플란트 피로시험에 관한 ISO/FPIS 14801:2003(E)규정을 참고하여 고정시켰다. 최소 하중은 10 N, 최대 하중은 250 N의 sine형 반복 하중을 $30^{\circ}$의 경사각도로, 하중 주기는 14 Hz로, 100만 회의 반복 하중을 적용한 후 풀림 회전력을 측정하였다. 결과: 1. 모든 시스템에서 지대주 나사의 풀림 회전력이 조임 회전력 보다 감소하였으나, 나사 풀림 현상은 나타나지 않았다. 2. 반복 하중 전과 후의 나사 풀림 회전력은 두 임플란트 시스템 모두에서 지르코니아 지대주가 금속 지대주보다 더 컸다(P<.05). 3. 반복 하중에 따른 풀림 회전력 상실률은 두 임플란트 시스템 모두에서 지르코니아 지대주와 금속 지대주가 차이가 없는 것으로 나타났다(P>.05). 4. 금속 지대주에서 반복 하중에 따른 풀림 회전력 상실률은 내측 연결 형태의 GS II 시스템이 외측 연결형태의 US II 시스템보다 작았다(P<.05). 5. 지르코니아 지대주에서는 반복 하중에 따른 풀림 회전력 상실률은 두 임플란트 시스템 간에 차이가 없는 것으로 나타났다(P>.05). 결론: 본 실험을 통해 100만회 반복 하중 하에서 지르코니아 지대주가 금속 지대주에 비해 나사 결합부 안정성이 더 크다는 결론을 내릴 수 있다.

• Restorative Dentistry and Endodontics
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• 제37권3호
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• pp.155-159
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• 2012

Objectives: To investigate the effect of dentin moisture degree and air-drying time on dentin-bond strength of two different one-step self-etching adhesive systems. Materials and Methods: Twenty-four human third molars were used for microtensile bond strength testing of G-Bond and Clearfil $S^3$ Bond. The dentin surface was either blot-dried or air-dried before applying these adhesive agents. After application of the adhesive agent, three different air drying times were evaluated: 1, 5, and 10 sec. Composite resin was build up to 4 mm thickness and light cured for 40 sec with 2 separate layers. Then the tooth was sectioned and trimmed to measure the microtensile bond strength using a universal testing machine. The measured bond strengths were analyzed with three-way ANOVA and regression analysis was done (p = 0.05). Results: All three factors, materials, dentin wetness and air drying time, showed significant effect on the microtensile bond strength. Clearfil $S^3$ Bond, dry dentin surface and 10 sec air drying time showed higher bond strength. Conclusions: Within the limitation of this experiment, air drying time after the application of the one-step self-etching adhesive agent was the most significant factor affecting the bond strength, followed by the material difference and dentin moisture before applying the adhesive agent.

• Restorative Dentistry and Endodontics
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• 제41권3호
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• pp.196-201
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• 2016

Objectives: The aim of this in vitro study was to evaluate the effect of incorporating three different nanobiomaterials into bleaching material on microhardness of bleached enamel. Materials and Methods: The crowns of 24 extracted sound human molars were sectioned. Sixty enamel specimens ($2{\times}3{\times}4 mm$) were selected and divided into five groups (n = 12): Group 1 received no bleaching procedure (control); Group 2 underwent bleaching with a 40% hydrogen peroxide (HP) gel; Groups 3, 4, and 5 were bleached with a 40% HP gel modified by incorporation of bioactive glass (BAG), amorphous calcium phosphate (ACP) and hydroxyapatite (HA), respectively. The enamel microhardness was evaluated. The differences in Knoop microhardness data of each group were analyzed by one-way ANOVA, followed by post hoc Tukey tests. Results: Significant differences were observed between the study groups. The enamel microhardness changes in Groups 1, 3, 4, and 5 were significantly lower than that of Group 2 (p < 0.001). Conclusions: Within the limitations of this study, it can be concluded that incorporation of each one of the three tested biomaterials as remineralizing agents might be effective in decreasing enamel microhardness changes subsequent to in-office bleaching.

• 한국정밀공학회지
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• 제28권1호
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• pp.80-88
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• 2011

The dental high-speed air turbine handpiece is one of the most popular devices that have been widely used as the main means of cutting tooth structure and restorative material in dentistry. In consideration of usage and marketability of the dental handpiece, it is obviously worthy of investigating it. The goal of this paper is to establish the relationship between the air turbine speed and the supply route inside the handpiece. To do this, the Computational Fluid Dynamics(CFD) tool, Fine$^{TM}$/Turbo is used and the optimal supply route position is suggested from the simulation results. In addition, as an attempt for domestic product, the reverse engineering process of a high speed dental handpiece by 3D X-Ray CT equipment and wire cutting is presented for the Mark II model in NSK. In doing so, the 3D modeling of the handpiece parts is carried out with CATIA V5, and the interference between parts is examined. Finally, the result of performance test for the prototype produced in this research is presented.

• Restorative Dentistry and Endodontics
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• 제9권1호
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• pp.127-132
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• 1983

The purpose of this study was to examine the sealing ability of the vitapex, when used with gutta-percha cone, as a root canal filling material. Fourty five canals from extracted human maxillary and mandibular teeth were randomly selected and instrumented in a conventional method with k-file. After instrumentation and dry the canal with paper points, the canals were divided into three groups and fifteen canals in each group were filled with the following materials; Vitapex, Vitapex in combination with gutta-percha cone, and Gutta-percha cone and Zinc-oxide Eugenol Cement. All the specimens were immersed in 2% methylenblue dye solution and the depth of dye penetration into the canals were evaluated by macroscope at the intervals of 1 day, 2days and 7days. The following results were obtained; 1. All the materials experimented showed varying degrees of dye penetration. 2. The canals filled with Vitapex and Vitapex in combination with gutta perch a cone revealed sudden increase of dye penetration with time passage compared to the canals obturated with Gutta-percha cone and Zinc-oxide eugenol cement. 3. In the canals filled with Vitapex, the mean dye penetration was 1.6mm at 1day, but the specimen exposed to the dye for 7days showed mean dye penetration of 9.2mm. 4. In the canals obturated with Vitapex and gutta-percha cone, the mean dye penetration was 2mm at 1day, 2.2mm at 2days, and 8mm at 7days.

• Restorative Dentistry and Endodontics
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• 제13권1호
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• pp.23-38
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• 1988

In order to investigate the material formed by application of fluoride on human dentin, exposed dentin of tooth cervix and sound dentin powder was treated by several fluoride solutions. The former was observed by scanning electron microscope and the latter was analysed by x-ray diffractometer and infrared spectrophotometer. The results obtained were as follows: 1. Application with NaF, $SnF_2$ and $Na_2PO_3F$ on exposed dentin of tooth cervix formed mineralized materials covered. 2. The amount of mineralized materials increased with time intervals of applying the fluorides. 3. The density of mineralized materials was highest in $Na_2PO_3F$ treatment group, and NaF treatment group was higher than $SnF_2$ treatment group. 4. $SnF_2$ remained in covering of mineralized materials. 5. Application with NaF and $Na_2PO_3F$ formed mineralized materials characterized apatitic crystals. 6. The crystallinity of mineralized materials was higher prominently in $Na_2PO_3F$ treatment group.

• Restorative Dentistry and Endodontics
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• 제16권2호
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• pp.118-125
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• 1991

Eighty - eight recently extracted teeth were used to evaluate the leakage characteristics of the following retrofilling materials; amalgam, zinc oxide eugenol cement, glass - ionomer cement, and cermet glass - ionomer cement. Root canals were prepared with step - back method and obturated with gutta percha and zinc oxide eugenol sealer. Root apex were resected 2 mm from apex and class I cavities were prepared with 2 mm or 4 mm depth. The cavities were filled with above materials. After application of varnish on all surface except resected surface, the roots were placed in 1 % methylene blue solution for 6 days. After longitudinal polishing to expose cental parts of filled materials, penetrated depths of dye were measured. The results were as follws. 1. As retrofilling material, glass ionomer cement filling groups showed less leakage than the other groups except zinc oxide eugenol cement filling group(p<0.01). 2. Amalgam filling groups had greater leakage than zinc oxide eugenol cement filling group(p<0.01). 3. 4 mm depth of retrofilled cavity had no effect on leakage characteristics compared with 2 mm depth cavity(p>0.05). 4. Glass ionomer cement and cermet glass ionomer cement filling groups showed less apical leakage than amalgam filling groups. But there was no statistical significance(p>0.05). 5. There was no difference in apical leakage between glass ionomer cement filling groups and cermet glass ionomer cement filling groups(p>0.05).