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Izabela Barszczewska-rybarek - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Novel Urethane-Dimethacrylate Monomer Containing Two Quaternary Ammonium Groups for Applications in Dentistry
Proceedings of 1st International Electronic Conference on Applied Sciences, 2020Co-Authors: Marta W. Chrószcz, Izabela Barszczewska-rybarekAbstract:The development of dental composites having antibacterial properties is one of the current trends in the restorative dentistry. It is justified by the need for the secondary caries reduction that is the main reason for dental restoration failure. In this field, the growing interest is associated with the development of quaternary ammonium monomers. In this study, we synthesized a novel Urethane-Dimethacrylate monomer containing two quaternary ammonium groups, via the three steps synthesis route. The synthesis procedure involved the transesterification of methyl methacrylate with the use of N-methyldiethanolamine, N-alkylation with the use of 1-bromohexadecane, and synthesis of Urethane-Dimethacrylate resin with the use of 2,4,4-trimethylhexamethylene diisocyanate. 1H NMR, 13C NMR, and ATR-FT IR analysis confirmed the chemical structure of the intermediate products and the structure of new Urethane-Dimethacrylate monomer.
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Novel Urethane-Dimethacrylate Monomers and Compositions for Use as Matrices in Dental Restorative Materials.
International journal of molecular sciences, 2020Co-Authors: Izabela Barszczewska-rybarek, Marta W. Chrószcz, Grzegorz ChladekAbstract:In this study, novel Urethane-Dimethacrylate monomers were synthesized from 1,3-bis(1-isocyanato-1-methylethyl)benzene (MEBDI) and oligoethylene glycols monomethacrylates, containing one to three oxyethylene groups. They can potentially be utilized as matrices in dental restorative materials. The obtained monomers were used to prepare four new formulations. Two of them were solely composed of the MEBDI-based monomers. In a second pair, a monomer based on triethylene glycol monomethacrylate, used in 20 wt.%, was replaced with triethylene glycol Dimethacrylate (TEGDMA), a reactive diluent typically used in dental materials. For comparison purposes, two formulations, using typical dental Dimethacrylates (bisphenol A glycerolate Dimethacrylate (Bis-GMA), Urethane-Dimethacrylate (UDMA) and TEGDMA) were prepared. The monomers and mixtures were tested for the viscosity and density. The homopolymers and copolymers, obtained via photopolymerization, were tested for the degree of conversion, polymerization shrinkage, water sorption and solubility, hardness, flexural strength and modulus. The newly developed formulations achieved promising physico-chemical and mechanical characteristics so as to be suitable for applications as dental composite matrices. A combination of the MEBDI-based Urethane-Dimethacrylates with TEGDMA resulted in copolymers with a high degree of conversion, low polymerization shrinkage, low water sorption and water solubility, and good mechanical properties. These parameters showed an improvement in relation to currently used dental formulations.
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The role of molecular structure on impact resistance and bending strength of photocured Urethane-Dimethacrylate polymer networks
Polymer Bulletin, 2017Co-Authors: Izabela Barszczewska-rybarekAbstract:The objective of this study was to investigate the influence of molecular structure on impact resistance ( a _n) and bending strength ( σ ) of photocured Urethane-Dimethacrylate polymer networks. Urethane-Dimethacrylate (UDMA) monomers were synthesized through reaction of oligoethylene glycol monomethacrylate (OEGMMA) with diisocyanate (DI). OEGMMA varied within the length of the oligooxyethylene chain, which consisted of one to four oxyethylene units. DI varied in chemical character: aliphatic, cycloaliphatic or aromatic. The molecular structure of UDMA polymers was characterized by X-ray powder diffraction, which allowed the calculation of the d -spacing ( d ) and dimensions of microgel agglomerates ( D ). The measurements of the polymerization shrinkage were used for the determination of the degree of conversion (DC), whereas the concentration of double bonds was used as a measure of the crosslink density ( q ). It was found that all structural parameters depend on the UDMA chemical structure. The increasing length of the oligooxyethylene chains caused the decrease in d and q , in contrast to the increase in D and DC. The DI chemical character caused the increase in the DC and q accordingly: symmetrical cycloaliphatic or aromatic
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The novel semi-biodegradable interpenetrating polymer networks based on Urethane-Dimethacrylate and epoxy-polyester components as alternative biomaterials.
Acta of bioengineering and biomechanics, 2015Co-Authors: Izabela Barszczewska-rybarek, Katarzyna Jaszcz, Sebastian Jurczyk, Grzegorz ChladekAbstract:PURPOSE This paper presents the pilot study aimed at the development of new full interpenetrating polymer networks based on Urethane- Dimethacrylate and biodegradable epoxy-polyester as the proposition of new biomaterials with gradually emerging porosity. METHODS The Urethane-Dimethacrylate monomer was obtained from 4,4'-methylenebis(phenyl isocyanate) and tetraethylene glycol monomethacrylate. The redox-initiating system was employed for its radical polymerization. The epoxy-polyester was produced by oxidation of the polyester, synthesized from succinic anhydride and allyl glicydyl ether. It was cured in a step-growth process with biogenic, aliphatic amine - spermidine. The mixtures of both monomers with adequate curing agents were room temperature polymerized. The hardened materials were characterized for damping behavior and dynamic modulus, hardness, water sorption, the course of hydrolytic degradation as well as the morphology - before and during the degradation process. RESULTS The cured materials revealed the nonporous, dense morphology. In the hydrolytic environment, the epoxy-polyester network degraded and the porous Urethane-Dimethacrylate scaffold remained. The epoxy-polyester appeared to prevent the Urethane-Dimethacrylate from attaining a high degree of conversion, even if the polymerization rate and the molecular mobility of the latter one are higher than those of the epoxy-polyester. The most homogeneous material with the best physico-mechanical properties was obtained when the Urethane-Dimethacrylate content was smaller than the epoxy-polyester content, respectively 25 and 50 wt%. CONCLUSIONS The system presented in this work could be useful in tissue engineering, where at the beginning of the tissue regeneration process it would meet the implant mechanical properties and then would deliver its porosity, facilitating the tissue regeneration process.
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Characterization of Urethane-Dimethacrylate derivatives as alternative monomers for the restorative composite matrix
Dental materials : official publication of the Academy of Dental Materials, 2014Co-Authors: Izabela Barszczewska-rybarekAbstract:Abstract Objective The aim was accomplished by a comparative analysis of the physicochemical properties of Urethane-Dimethacrylate (UDMA) monomers and their homopolymers with regard to the properties of basic Dimethacrylates used presently in dentistry. The homologous series of UDMA were obtained from four oligoethylene glycols monomethacrylates (HEMA, DEGMMA, TEGMMA and TTEGMMA) and six diisocyanates (HMDI, TMDI, IPDI, CHMDI, TDI and MDI). Methods Photopolymerization was light-initiated with the camphorquinone/tertiary amine system. Monomers were tested for viscosity and density. Flexural strength, flexural modulus, hardness, water sorption and polymerization shrinkage of the polymers were studied. The glass transition temperature and the degree of conversion were also discussed. Results HEMA/IPDI appeared to be the most promising alternative monomer. The monomer exhibited a lower viscosity and achieved higher degree of conversion, the polymer had lower water sorption as well as higher modulus, glass temperature and hardness than Bis-GMA. The polymer of DEGMMA/CHMDI exhibited lower polymerization shrinkage, lower water sorption and higher hardness, however it exhibited lower modulus when compared to HEMA/TMDI. The remaining monomers obtained from HEMA were solids. Monomers with longer TEGMMA and TTEGMMA units polymerized to rubbery networks with high water sorption. The viscosity of all studied UDMA monomers was too high to be used as reactive diluents. Significance The systematic, comparative analysis of the homologous UDMA monomers and corresponding homopolymers along with their physico-mechanical properties are essential for optimizing the design process of new components desirable in dental formulations. Some of the studied UDMA monomers may be simple and effective alternative Dimethacrylate comonomers.
Gilbert Bannach - One of the best experts on this subject based on the ideXlab platform.
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A deep investigation into the thermal degradation of Urethane Dimethacrylate polymer
Journal of Thermal Analysis and Calorimetry, 2021Co-Authors: Rafael Turra Alarcon, Caroline Gaglieri, Giovanny Carvalho Santos, Juan Carlos Roldao, Aroldo Geraldo Magdalena, Luiz Carlos Silva-filho, Gilbert BannachAbstract:This work investigates in depth the thermal degradation process of a polymer of Urethane Dimethacrylate (UDMA). UDMA monomer has been widely used in dental restorations and biomaterials. The use of density functional theory (DFT) calculations provided the bases for understanding the structure and reactivity of the UDMA monomer. Simultaneous thermogravimetry–differential thermal analysis, Photovisual Differential Scanning Calorimetry, and mid-infrared spectroscopy (MIR) were used to examine the depolymerization and degradation process. Non-isothermal kinetics made it possible to determine the best fit ( n -dimensional nucleation according to Avrami–Erofeev followed by two competitive processes: n th order with autocatalysis by-product and reaction of nth order). Furthermore, the UDMA-P lifetime (5%) was calculated to show a degradation time of 3 years at 100.0 °C. Notwithstanding, techniques such as MIR and nuclear magnetic resonance ^13C, ^1H linked to DFT calculations helped to elucidate the cleavage positions and possible degradation by-products of UDMA degradation.
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Effect of metal oxide fillers in Urethane Dimethacrylate polymer with glycerol obtained by photopolymerization synthesis
Journal of Polymer Research, 2020Co-Authors: Ana Beatriz Benites, Rafael Turra Alarcon, Caroline Gaglieri, Katie J. Lamb, Gilbert BannachAbstract:Urethane Dimethacrylate (UDMA) is a monomer widely used in photopolymerization reactions to produce biomaterials, due to its advantageous properties such as mechanical resistance and relatively low viscosity. However, this monomer is expensive. Reducing the quantity of UDMA monomer required to obtain the final polymer, without losing its main properties, is essential not just in terms of costs but also green chemistry principles. It has been demonstrated that glycerol inclusion into the polymeric matrix during polymerization is one way to achieve this goal. Thus, this work proposes the insertion of glycerol and metal oxide fillers (Al2O3, TiO2, Nb2O5, La2O3 and ZrO2) in the photopolymerization of Urethane Dimethacrylate, with the aim to study how these effects the degree of conversion, as well as the thermal properties of the final polymer. The thermal properties were evaluated using simultaneous thermogravimetry–differential thermal analysis (TG–DTA) and differential scanning calorimetry (DSC). The degree of conversion/rate of polymerization was calculated using mid-infrared spectroscopy (MIR). The polymers filled with Al2O3, TiO2, Nb2O5 and La2O3 exhibited good conversion values of 87.42, 78.47, 77.64 and 75.51%, respectively. For all polymers synthesized, no significant changes were observed in their thermal stability. Lastly, it is suggested that the incorporation of the oxides in the monomeric mixture correlate to the degree of conversion, with scanning electronic microscopy (SEM) analysis suggesting oxide dispersion interferes with the morphology of the polymer.
Michaël Sadoun - One of the best experts on this subject based on the ideXlab platform.
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Optimum pressure for the high-pressure polymerization of Urethane Dimethacrylate
Dental materials : official publication of the Academy of Dental Materials, 2015Co-Authors: Anh Chi Phan, Pascal Béhin, Grégory Stoclet, N. Dorin Ruse, Jean-françois Nguyen, Michaël SadounAbstract:Abstract Objectives The aim of this study, part of our research to improve properties of resin composite blocks suitable for CAD/CAM and to better understand underlying mechanisms associated with high-temperature/high-pressure (HT/HP) polymerization, was to determine an optimum polymerization pressure of Urethane Dimethacrylate (UDMA) in the presence of an initiator (0.5% benzoyl peroxide) by determining the degree of conversion (DC) and viscoelastic properties of polymers obtained at 90 °C under varying HP. Methods DC and viscoelastic properties of 16 UDMA polymers, two controls (thermo-cured and thermo-cured followed by post-cure relaxation) and 14 experimental groups (HP polymers, in the range of 50–350 MPa, in 50 MPa increments, without and with post-cure relaxation) were determined via near infrared spectroscopic analysis and dynamic mechanical analysis, respectively. Results The results have shown that HP UDMA polymers have DC superior to that of the control group. With regards to E′ and E″, the results have shown no significant difference between control and HP polymers. The damping factor, tan δ, decreased with increasing pressure, while E ′ rub and Tg increased. Polymerization at 150 MPa or higher resulted in significantly higher E ′ rub and Tg. Significance The results of this study suggested that HP polymerization at 90 °C of UDMA reduced the number of defects and the free volume, leading to a more homogeneous polymer network. The results have also suggested that 200 MPa is an optimum polymerization pressure, resulting in polymers with significantly higher DC, E ′ rub , and Tg, while maintaining adequate damping capacity (tan δ).
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Dynamic mechanical analysis of high pressure polymerized Urethane Dimethacrylate.
Dental materials : official publication of the Academy of Dental Materials, 2014Co-Authors: Pascal Béhin, Grégory Stoclet, N. Dorin Ruse, Michaël SadounAbstract:Abstract Objectives The aim of this study was to compare the viscoelastic properties of high pressure (HP) polymerized Urethane Dimethacrylate (UDMA) with those of control, ambient pressure thermo-polymerized and photo-polymerized, UDMA and to assess the effect of varying polymerization parameters (protocol, temperature, and initiator) on the viscoelastic properties of HP polymerized UDMA. Methods The viscoelastic properties of the two control polymers, polymerized under atmospheric pressure, and four experimental polymers, polymerized under HP, were determined via dynamic mechanical analysis (DMA), in three point bending configuration. Atomic force microscopy (AFM) was used to characterize fractured polymer surface morphologies. Results The results showed that: HP-polymerization lead to a polymer with significantly higher T g and E ′ rub , indicative of a higher crosslink density; modifying the polymerization protocol resulted in a significant increase in tan δ ; increasing the polymerization temperature lead to a significant decrease in E ′ rub and T g ; and that the polymer with no initiator had the lowest E ′, E ″, T g , and E ′ rub and the highest tan δ , suggesting that under this conditions a polymer with significantly reduced crosslink density had been obtained. A characteristic nodular appearance was seen for the two control polymers under AFM, while a modified surface morphology was present in the case of HP polymerized materials. Significance The DMA results suggest that polymerization under HP resulted in polymers with an increased crosslink density and that the higher polymerization temperature or the lack of initiator was detrimental to the viscoelastic properties determined. Changes in polymer network morphology were identified by AFM characterization.
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high temperature high pressure polymerized Urethane Dimethacrylate mechanical properties and monomer release
Dental Materials, 2014Co-Authors: Anh Chi Phan, Jean-françois Nguyen, Mie-leng Tang, Dorin N Ruse, Michaël SadounAbstract:Abstract Objective This study was conducted to determine selected mechanical/physical properties of and monomer release from high-temperature high-pressure (HT/HP) polymerized Urethane Dimethacrylate (UDMA). Methods Flexural strength (σf), hardness, fracture toughness (KIC), and density (ρ) were determined for five UDMA resin blocks produced via different polymerization protocols. High performance liquid chromatography (HPLC) was used to determine monomer release from the five polymers. One way ANOVA, Scheffe multiple means comparisons (α = 0.05), and Weibull statistics (for σf) were used to analyze the results. Results The results showed that HT/HP polymerization resulted in a significant (p Significance The results of this study suggest that HT/HP polymerization affects the network structure and leads to UDMA polymers with improved mechanical/physical properties and with dramatically reduced monomer release. The low elution of monomers from HT/HP and HP polymerized materials suggests the achievement of a higher degree of conversion and a lesser degree of inhomogeneity with regards to microgel domains. The results, however, cannot fully explain the dramatic increase in mechanical/physical properties reported previously for RCB, improvements that may be due to a better filler-matrix interaction afforded by HT/HP polymerization.
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High-temperature high-pressure polymerized Urethane Dimethacrylate-mechanical properties and monomer release.
Dental materials : official publication of the Academy of Dental Materials, 2014Co-Authors: Anh Chi Phan, N. Dorin Ruse, Jean-françois Nguyen, Mie-leng Tang, Michaël SadounAbstract:Abstract Objective This study was conducted to determine selected mechanical/physical properties of and monomer release from high-temperature high-pressure (HT/HP) polymerized Urethane Dimethacrylate (UDMA). Methods Flexural strength ( σ f ), hardness, fracture toughness ( K IC ), and density ( ρ ) were determined for five UDMA resin blocks produced via different polymerization protocols. High performance liquid chromatography (HPLC) was used to determine monomer release from the five polymers. One way ANOVA, Scheffe multiple means comparisons ( α = 0.05), and Weibull statistics (for σ f ) were used to analyze the results. Results The results showed that HT/HP polymerization resulted in a significant ( p σ f and ρ , along with an increase in Weibull modulus. No significant differences were found in hardness and K IC between the two HT/HP polymerized materials. A significantly lower ( p Significance The results of this study suggest that HT/HP polymerization affects the network structure and leads to UDMA polymers with improved mechanical/physical properties and with dramatically reduced monomer release. The low elution of monomers from HT/HP and HP polymerized materials suggests the achievement of a higher degree of conversion and a lesser degree of inhomogeneity with regards to microgel domains. The results, however, cannot fully explain the dramatic increase in mechanical/physical properties reported previously for RCB, improvements that may be due to a better filler-matrix interaction afforded by HT/HP polymerization.
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Properties of experimental Urethane Dimethacrylate-based dental resin composite blocks obtained via thermo-polymerization under high pressure.
Dental materials : official publication of the Academy of Dental Materials, 2013Co-Authors: Jean-françois Nguyen, N. Dorin Ruse, Véronique Migonney, Michaël SadounAbstract:Abstract Objectives The aim of this study was to use high-pressure high-temperature (HP/HT) polymerization to produce Urethane Dimethacrylate (UDMA)–triethylene glycol Dimethacrylate (TEGDMA) based resin composite blocks (RCB) suitable for dental computer-aided design/manufacture (CAD/CAM) applications and to compare their physical/mechanical properties to those of a commercial dental RCB. The null hypotheses tested were: (1) there are no differences in the physical/mechanical properties between HP/HT polymerized UDMA-TEGDMA RCB and a commercial RCB; (2) volume fraction filler (Vf) does not affect the physical/mechanical properties of HP/HT polymerized RCB. Methods Four UDMA-based experimental RCB were manufactured under HP/HT conditions. A RCB manufactured under the same HP/HT conditions from a commercial resin composite (Z100) and its commercial counterpart CAD/CAM RCB (Paradigm MZ100) were used as controls. Flexural strength (σf), fracture toughness (KIC), and hardness were determined. The results were analyzed using one-way ANOVA, Scheffe multiple means comparisons (α = 0.05), and Weibull statistics (for σf). Scanning electron microscopy was used to characterize fractured surfaces. Results All HP/HT polymerized RCB had superior σf, KIC, and Weibull modulus compared to the commercial dental RCB. The experimental RCB had similar or superior properties compared to HP/HT polymerized Z100 RCB. Fewer and smaller porosities (not quantified) were apparent in HP/HT polymerized RCB. The experimental RCB that contained 65% Vf showed higher porosity, suggesting practical difficulties in filler incorporation beyond a certain Vf. Conclusions The results of this study suggested that RCB suitable for dental CAD/CAM applications could be obtained by HP/HT polymerization of resin composites based on pure UDMA.
Irini D. Sideridou - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and study of physical properties of dental light-cured nanocomposites using different amounts of a Urethane Dimethacrylate trialkoxysilane coupling agent
Dental materials : official publication of the Academy of Dental Materials, 2011Co-Authors: Maria M. Karabela, Irini D. SideridouAbstract:a b s t r a c t Objective. The purpose of this work was the study of the effect of the amount of a Urethane Dimethacrylate silane (UDMS) coupling agent on physical properties of dental light-cured resin nanocomposites based on Bis-GMA/TEGDMA (50/50 wt/wt) matrix and Aerosil OX50 as filler. Methods. Silica nanoparticles (Aerosil OX 50) used as filler were silanized with 5 different amounts of UDMS 1.0, 2.5, 5.0, 7.5 and 10 wt% relative to silica. The silanizated silica nanoparticles were identified by FT-IR spectroscopy and thermogravimetric analysis (TGA). Then the silanized nanoparticles (60 wt%) were mixed with a Bis-GMA/TEGDMA (50/50 wt/wt) matrix. Degree of conversion of light cured composites was determined by FT-IR analysis. The static flexural strength and flexural modulus were measured using a three-point bending set up. The dynamic thermomechanical properties were determined by DMA analyzer. Measurements were taken in samples stored, immediately after curing, in water at 37 ◦ C for 24 h. Sorption, solubility and volumetric change were determined after storage of composites in water or ethanol/water of 75 vol% for 30 days. Thermogravimetric analysis of composites was performed in nitrogen atmosphere from 50 to 800 ◦C.
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Thermal degradation and isoconversional kinetic analysis of light-cured Dimethacrylate copolymers
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Dimitris S. Achilias, Maria M. Karabela, Irini D. SideridouAbstract:Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated Dimethacrylate (Bis-EMA) with triethylene glycol Dimethacrylate (TEGDMA), and Urethane Dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins. Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the formation of weak links inside the polymeric network.
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Reactivity of Benzoyl Peroxide/Amine System as an Initiator for the Free Radical Polymerization of Dental and Orthopaedic Dimethacrylate Monomers: Effect of the Amine and Monomer Chemical Structure
Macromolecules, 2006Co-Authors: Irini D. Sideridou, Dimitris S. Achilias, Olga KaravaAbstract:The free radical homopolymerization of Bis-phenol-A-bis(glycidyl methacrylate) (Bis-GMA), a Urethane Dimethacrylate (UDMA), and triethylene glycol Dimethacrylate (TEGDMA) induced by a benzoyl perox...
Bum-soon Lim - One of the best experts on this subject based on the ideXlab platform.
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Urethane Dimethacrylate Influences the Cariogenic Properties of Streptococcus Mutans
Materials (Basel Switzerland), 2021Co-Authors: Kyungsun Kim, Bum-soon Lim, Jeong Nam Kim, Sug-joon AhnAbstract:Concerns regarding unbound monomers in dental composites have increased with the increased usage of these materials. This study assessed the biological effects of Urethane Dimethacrylate (UDMA), a common monomer component of dental composite resins, on the cariogenic properties of Streptococcus mutans. Changes in the growth rate, biofilm formation, interaction with saliva, surface hydrophobicity, adhesion, glucan synthesis, sugar transport, glycolytic profiles, and oxidative- and acid-stress tolerances of S. mutans were evaluated after growing the cells in the presence and absence of UDMA. The results indicated that UDMA promotes the adhesion of S. mutans to the underlying surfaces and extracellular polysaccharide synthesis, leading to enhanced biofilm formation. Furthermore, UDMA reduced the acid tolerance of S. mutans, but enhanced its tolerance to oxidative stress, thus favoring the early stage of biofilm development. UDMA did not significantly affect the viability or planktonic growth of cells, but diminished the ability of S. mutans to metabolize carbohydrates and thus maintain the level of intracellular polysaccharides, although the tendency for sugar transport increased. Notably, UDMA did not significantly alter the interactions of bacterial cells with saliva. This study suggests that UDMA may potentially contribute to the development of secondary caries around UDMA-containing dental materials by prompting biofilm formation, enhancing oxidative tolerance, and modulating carbon flow.
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Dynamic Mechanical Properties of a Visible Light Curable Urethane Dimethacrylate Based Dental Resin
Polymer Journal, 2003Co-Authors: Jong Keun Lee, Ji Young Kim, Bum-soon LimAbstract:The purpose of this study was to evaluate dynamic mechanical properties of Urethane Dimethacrylate (UDMA) and triethylene glycol Dimethacrylate (TEGDMA) based dental resin. Dynamic mechanical properties of a visible light (λ=400–500 nm) curable UDMA/TEGDMA (70:30 in wt%) resin were investigated for specimens uncured, light-cured for 40s, and heated to 175°C subsequent to the irradiation for 40s. Differential scanning calorimetry (DSC) was also employed as a complementary technique. For the light-cured specimen, two abrupt drops in the log storage modulus (E’) and two peaks in the tanδ vs. temperature curve corresponding to the glass transition were observed. The storage modulus was slightly increased with increasing temperature between the two modulus drops. The DSC experiment showed that the light-cured specimen contains residual living groups trapped by the fast reaction, which lead to further reaction during post-cure heat treatment. This further thermal reaction is considered to be responsible for the modulus increase. After heating to 175°C above the DSC exothermic peak, most of the residual groups in the light-cured specimen were found to be reacted, showing a single decrease in modulus and a single peak in the tan δ curve, and no exotherm in the DSC curve. With the aid of DSC data, the further thermal cure reaction with increasing temperature may occur within the glass transition region. The occurrence of the thermal reaction gives rise to the inaccuracy in determining the glass transition temperature (Tg).
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Determination of Residual Monomers in Dental Pit and Fissure Sealants Using Food/Oral Simulating Fluids
2000Co-Authors: Hyun-jung Moon, Bum-soon Lim, Yong-keun Lee, Cheol-we KimAbstract:Bum-Soon Lim, Yong-Keun Lee, and Cheol-We KimDepartment of Dental Biomaterials and Dental Research Institute, College of Dentistry,Seoul National University, Seoul 110-749, KoreaReceived August 14, 2000Specimens were cured by using a 1 mm (thickness) ×5 mm (diameter) teflon mold, and were immersed in ar-tificial saliva and in 75% ethanol for 1, 7, 14, 21 and 28 days in order to quantify and to identify toxic compo-nents and to determine any degradation byproducts of Bis-GMA that might be released from five commerciallyavailable resin-based dental sealants. In artificial saliva, the only released component was triethylene glycoldimethacylate (TEGDMA). In 75% ethanol, TEGDMA, 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (Bis-GMA) and Urethane Dimethacrylate (UDMA) were released highly at the initial stage, in-dicating that the amount of component released is not linearly correlated with the immersion time. The amountof released TEGDMA was found to be much higher in 75% ethanol than in artificial saliva. Importantly,bisphenol-A (BPA) was detected from all the uncured sealants tested, suggesting that all the sealants tested con-tain BPA as a contaminant. Introduction2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (Bis-GMA), Urethane Dimethacrylate (UDMA), tri-ethylene glycol dimethacylate (TEGDMA), benzoyl per-oxide and methyl methacrylate are the major components ofresin-based dental materials.
