• 공업화학
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• 제21권3호
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• pp.252-257
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• 2010

본 연구에서는 PMMA와 SMA의 블렌드에 몬모릴로나이트(PM) 또는 유기화제로 개질된 clay (Cloisite 25A 또는 15A)를 첨가하여 PMMA/SMA/clay 나노복합재료를 제조하였다. 이 나노복합재료에서 clay가 블렌드의 상용성에 주는 영향에 대해 SMA 중의 MA의 함량을 변화시키며 연구하였다. 나노복합재료 제조 시 용매로는 MEK와 chloroform을 이용하여 용매가 주는 영향에 대해서도 조사하였다. DSC 측정을 이용하여 유리전이온도와 유리전이온도의 폭을 분석한 결과 clay의 첨가로 인해 PMMA/SMA 블렌드의 상용성이 향상되는 것을 확인하였으며 특히 15A가 가장 상용성 증진에 효과적인 것으로 나타났다. 이 결과는 MA의 함량을 7, 14, 32, 43%로 변화시킨 모든 SMA의 경우에 대해 동일하였다. XRD와 TEM을 이용하여 고분자 내에서의 clay의 분산 상태를 관찰하였는데 역시 15A를 포함하는 나노복합재료에서 clay가 가장 효과적으로 분산되어 있음을 확인하였다.

• The Journal of Advanced Prosthodontics
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• 제4권1호
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• pp.1-6
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• 2012

PURPOSE. The aim of this study was to compare the flexural strength of polymethyl methacrylate (PMMA) and bis-acryl composite resin reinforced with polyethylene and glass fibers. MATERIALS AND METHODS. Three groups of rectangular test specimens (n = 15) of each of the two resin/fiber reinforcement were prepared for flexural strength test and unreinforced group served as the control. Specimens were loaded in a universal testing machine until fracture. The mean flexural strengths (MPa) was compared by one way ANOVA test, followed by Scheffe analysis, using a significance level of 0.05. Flexural strength between fiber-reinforced resin groups were compared by independent samples t-test. RESULTS. For control groups, the flexural strength for PMMA (215.53 MPa) was significantly lower than for bis-acryl composite resin (240.09 MPa). Glass fiber reinforcement produced significantly higher flexural strength for both PMMA (267.01 MPa) and bis-acryl composite resin (305.65 MPa), but the polyethylene fibers showed no significant difference (PMMA resin-218.55 MPa and bis-acryl composite resin-241.66 MPa). Among the reinforced groups, silane impregnated glass fibers showed highest flexural strength for bis-acryl composite resin (305.65 MPa). CONCLUSION. Of two fiber reinforcement methods evaluated, glass fiber reinforcement for the PMMA resin and bis-acryl composite resin materials produced highest flexural strength. Clinical implications. On the basis of this in-vitro study, the use of glass and polyethylene fibers may be an effective way to reinforce provisional restorative resins. When esthetics and space are of concern, glass fiber seems to be the most appropriate method for reinforcing provisional restorative resins.

• The Journal of Advanced Prosthodontics
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• 제6권3호
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• pp.207-214
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• 2014

PURPOSE. This study characterized the synthesis of a modified PMMA (Polymethyl methacrylate) denture acrylic loading platinum nanoparticles (PtN) and assessed its bacterial inhibitory efficacy to produce novel antimicrobial denture base material. MATERIALS AND METHODS. Polymerized PMMA denture acrylic disc ($20mm{\times}2mm$) specimens containing 0 (control), 10, 50, 100 and 200 mg/L of PtN were fabricated respectively. The obtained platinum-PMMA nanocomposite (PtNC) was characterized by TEM (transmission electron microscopy), SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), thermogravimetric and atomic absorption spectrophotometer analysis. In antimicrobial assay, specimens were placed on the cell culture plate, and $100{\mu}L$ of microbial suspensions of S. mutans (Streptococcus mutans) and S. sobrinus (Streptococcus sobrinus) were inoculated then incubated at $37^{\circ}C$ for 24 hours. The bacterial attachment was tested by FACS (fluorescence-activated cell sorting) analysis after staining with fluorescent probe. RESULTS. PtN were successfully loaded and uniformly immobilized into PMMA denture acrylic with a proper thermal stability and similar surface morphology as compared to control. PtNC expressed significant bacterial anti-adherent effect rather than bactericidal effect above 50 mg/L PtN loaded when compared to pristine PMMA (P=.01) with no or extremely small amounts of Pt ion eluted. CONCLUSION. This is the first report on the synthesis and its antibacterial activity of Pt-PMMA nanocomposite. PMMA denture acrylic loading PtN could be a possible intrinsic antimicrobial denture material with proper mechanical characteristics, meeting those specified for denture bases. For clinical application, future studies including biocompatibility, color stability and warranting the long-term effect were still required.

• 대한소아치과학회지
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• 제25권2호
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• pp.259-267
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• 1998

For more than two decades, many investigators have tried a variety of methods for delivering antimicrobial agents to the oral cavity with the objective of eliminating mutans streptococci. In the belief that the effectiveness of chemotherapy might be improved by a more effective delivery system, the intention of the present study was to exploit a new drug delivery system delivering chlorhexidine to the oral cavity. The vehicle delivering chlorhexidine tested in this study was self-curing acrylic resin(polymethyl methacrylate). The powder of the acrylic resin was polymerized with the 5 different liquid preparations, in which $Chlorzoin^{(R)}$ was mixed with five different monomer/Chlorzoin ratios immediately prior to the polymerization, in a stainless steel mold ($40mm{\times}40mm{\times}2mm$). A total of 50 cured resin specimens were divided into 5 groups according to the different monomer preparations. Every specimen was soaked in an airtight container filled with distilled water (100 ml) and then kept in an incubator at $37^{\circ}C$. The solutions (0.8 ml) were collected from the container at every 24 hours, and the amount of released chlorhexidine in the solutions was measured in an ultraviolet spectrophotometer at 250nm. The container was refilled with distilled water every after measurement. This procedure was repeated for 14 days. It was found that chlorhexidine was continuously released from all of the 50 specimens during the experimental period. And it was noted that the pattern of chlorhexidine release was a type of sustained-release preparation, that is, the amount of the released chlorhexidine at the first day in all 5 groups was high (p<0.0001), and then the release was decreased during the rest of the experimental period (p<0.001).

• 한국농공학회논문집
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• 제60권1호
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• pp.101-110
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• 2018

This study experimentally investigated the compressive and flexyral strength development characteristics of polymer concrete using four different type polymeric resins such as unsaturated polyester, vinyl ester, epoxy, and PMMA (polymethyl methacrylate) as binders. The test results show that the average compressive strength of those four different polymer concretes was 88.70 MPa, the average flexural strength was 20.30 MPa. Those test results show that compressive and flexural strengths of polymer concrete were much stronger than compressive and flexural strengths of ordinary Portland cement concrete. In addition, the relative gains of the compressive strength development at the age of 24 hrs compared to the age of 168 hrs were 68.6~88.3 %. Also, the relative gains of the flexural strength development at the age of 24 hrs compared to the age of 168 hrs were 73.8~93.4 %. These test results show that compressive and flexural strengths of each polymer concrete tested in this study were developed at the early age. Moreover, the prediction equations of compressive and flexural strength developments regarding the age were determined. The determined prediction equations could be applied to forecast the compressive and flexural strength developments of polymer concrete investigated in this study because those prediction equations have the high coefficients of correlation. Last, the relations between the compressive strength and the flexural strength of polymer concrete were determined and the flexural/compressive strength ratios were from 1/4 to 1/5. These results show that polymer concretes investigated in this study were appropriate as a flexural member of a concrete structure because the flexural/compressive strength ratios of polymer concrete were much higher than the flexural/compressive strength ratios of Portland cement concrete.

• 대한치과보철학회지
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• 제39권3호
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• pp.282-296
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• 2001

The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light curing resin and autopolymerizing polymethyl methacrylate resin custom tray material was investigated. Custom trays were fabricated from a master cast that had three index points marked on both inner and outer vestibules and then poured in yellow stone. The distance between the reproduced index points were measured to be ${\pm}0.001mm$ with a measuring microscope and the algebraic norms calculated for each tray material. No differences were found in the algebraic norms of inner and outer dimensions for upper tray impressions by ANOVA(p>0.05). However, T-test revealed that there were differences between upper and lower impressions and Tukey's hsd test revealed that in lower tray impressions, the Palatray in inner, the Lightplast in outer dimensions respectively were different from other materials. The index points reproduced on the casts compared with the master cast, were closer together for upper tray impressions. All four tray materials produced acceptable casts, 1. Algebraic norms of inner and outer dimensions of the test casts for upper trays were not statistically different irrespective of materials.(P>0.05) 2. T-test showed that there were differences between means with upper and lower trays especially in outer dimension.(P>0.05) 3. But, algebraic norms of inner and outer dimensions of the test casts for lower trays were statistically different between materials. 4. Palatray XL in inner, Lightplast-platten in outer dimensions respectively for lower trays were different from other materials, but, the nearest to the original model.

• 대한치과보철학회지
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• 제45권6호
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• pp.724-734
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• 2007

Statement of problem. Translucency and masking effect of provisional crown and fixed partial denture materials is an important esthetic consideration. But, provisional resin materials differ substantially in their ability to mask underlying colors. Purpose. The purpose of this study was to evaluate the translucency differences of provisional resin materials at various thicknesses and the correlation between the translucency and the masking efficiency. Material and methods. Two polymethyl methacrylate resins (Jet Tooth Shade, Alike) and three resin composites (Protemp 3 Garant, Luxatemp and Revotek LC) were used. Specimens (n=6) were fabricated from each material in 0.3, 0.5, 0.8, 1.0, 1.5, 2.0 and 3.0 mm thickness. The CIELAB parameters of each specimens were measured using a spectrophotometer. The translucency parameter (TP) values and the masking effect $({\Delta}ME^*{_{ab}})$ values were computed and all data were statistically analyzed by one-way ANOVA and the multiple comparisons Scheffe test. The correlation between the thickness and the TP values and the correlation between the thickness and the ${\Delta}ME^*{_{ab}}$ values were also evaluated by correlation analysis and regression analysis. Results. The TP values and the ${\Delta}ME^*{_{ab}}$ values were significantly related to the thickness in all specimens. The TP values were more sensitive to the change of thickness than the ${\Delta}ME^*{_{ab}}$ values. The order of the translucency by brand was different from the order of the masking effect by brand in all thickness groups. Conclusion. Within the limitations of this study, the translucency and masking effect of the provisional resin materials investigated were significantly related to their thickness. The masking effect of provisional resin was correlated with the translucency parameter, but the order of the masking effect by brand was different from the order of the translucency parameter.

• 한국세라믹학회지
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• 제53권6호
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• pp.604-609
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• 2016

This study reports on wet-foam stability with respect to porous ceramics from a particle-stabilized colloidal suspension that is achieved through the addition of polymethyl methacrylate (PMMA) using a wet process. To stabilize the wet foam, an initial colloidal suspension of $Al_2O_3$ was partially hydrophobized by the surfactant propyl gallate (2 wt.%) and $SiO_2$ was added as a stabilizer. The influence of the PMMA content on the bubble size, pore size, and pore distribution in terms of the contact angle, surface tension, adsorption free energy, and Laplace pressure are described in this paper. The results show a wet-foam stability of more than 83%, which corresponds to a particle free energy of $2.7{\times}10^{-12}J$ and a pressure difference of 61.1 mPa for colloidal particles with 20 wt.% of PMMA beads. It was possible to control the uniform distribution of the open/closed pores by increasing the PMMA content and by adding thick struts, leading to the achievement of a higher-stability wet foam for use in porous ceramics.

• Smart Structures and Systems
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• 제17권2호
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• pp.297-311
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• 2016

Based on the distributed fiber optic sensing (DFOS) technique, plastic optical fibers (POFs) are attractive candidates to measure deformations of geotechnical structures because they can withstand large strains before rupture. Understanding the mechanical interaction between an embedded POF and the surrounding soil or rock is a necessary step towards establishing an effective POF-based sensing system for geotechnical monitoring. This paper describes a first attempt to evaluate the feasibility of POF-based soil deformation monitoring considering the POF-soil interfacial properties. A series of pullout tests were performed under various confining pressures (CPs) on a jacketed polymethyl methacrylate (PMMA) POF embedded in soil specimens. The test results were interpreted using a fiber-soil interaction model, and were compared with previous test data of silica optical fibers (SOFs). The results showed that the range of CP in this study did not induce plastic deformation of the POF; therefore, the POF-soil and the SOF-soil interfaces had similar behavior. CP was found to play an important role in controlling the fiber-soil interfacial bond and the fiber measurement range. Moreover, an expression was formulated to determine whether a POF would undergo plastic deformation when measuring soil deformation. The plasticity of POF may influence the reliability of measurements, especially for monitored geo-structures whose deformation would alternately increase and decrease. Taken together, these results indicate that in terms of the interfacial parameters studied here the POF is feasible for monitoring soil deformation as long as the plastic deformation issue is carefully addressed.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.110-117
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• 2013

PURPOSE. Polymethyl methacrylate (PMMA) is the most commonly used denture base material despite typically low in strength. The purpose of this study was to improve the physical properties of the PMMA based denture base resins (QC-20, Dentsply Ltd., Addlestone, UK; Stellon, AD International Ltd, Dentsply, Switzerland; Acron MC; GC Lab Technologies Inc., Alsip, Japan) by copolymerization mechanism. MATERIALS AND METHODS. Control group specimens were prepared according to the manufacturer recommendations. In the copolymer groups; resins were prepared with 5%, 10%, 15% and 20% acrylamide (AAm) (Merck, Hohenbrunn, Germany) content according to the moleculer weight ratio, respectively. Chemical structure was characterized by a Bruker Vertex-70 Fourier transform infrared spectroscopy (FTIR) (Bruker Optics Inc., Ettlingen, Germany). Hardness was determined using an universal hardness tester (Struers Duramin, Struers A/S, Ballerup, Denmark) equipped with a Vickers diamond penetrator. The glass transition temperature ($T_g$) of control and copolymers were evaluated by Perkin Elmer Diamond DSC (Perkin Elmer, Massachusetts,USA). Statistical analyses were carried out using the statistical package SPSS for Windows, version 15.0 (SPSS, Chicago, IL, USA). The results were tested regarding the normality of distribution with the Shapiro Wilk test. Data were analyzed using ANOVA with post-hoc Tukey test (P<.01). RESULTS. The copolymer synthesis was confirmed by FTIR spectroscopy. Glass transition temperature of the copolymer groups were higher than the control groups of the resins. The 10%, 15% and 20% copolymer groups of Stellon presented significantly higher than the control group in terms of hardness. 15% and 20% copolymer groups of Acron MC showed significantly higher hardness values when compared to the control group of the resin. Acrylamide addition did not affect the hardness of the QC-20 resin significantly. CONCLUSION. Within the limitation of this study, it can be concluded that copolymerization of PMMA with AAm increased the hardness value and glass transition temperature of PMMA denture base resins.