Microwave Polymerization Research Articles

Mechanical properties of conventional versus microwave-polymerized denture base acrylic resins

New denture base acrylic resins have been introduced that are specifically formulated for microwave polymerization. Microwave polymerization is a time-efficient procedure, but few studies have evaluated how these new acrylic resin formulations compare with conventionally processed acrylic resins. The purpose of this in vitro study was to compare the stiffness and strength of denture base acrylic resins formulated for microwave polymerization with conventionally processed acrylic resin. Rectangular beams were fabricated from 2 microwave-polymerized denture base acrylic resins, microwave-specific resin (Nature-Cryl MC), resin with the option of microwave polymerization (Diamond D), and a conventionally processed resin as a control (Lucitone 199). Specimens (n=10) were stored in water for 1 week and subjected to a 3-point bend test to determine the flexural modulus (stiffness) and flexural strength before (initial properties) or after 120 000 load cycles. The load cycles, conducted between 5 and 25N at 2Hz, simulated 6 months of mastication. Data were analyzed by using 2-way ANOVA, followed by pairwise comparisons (α=.05). The initial flexural modulus (mean ±standard deviation) was conventionally processed resin, 2.65 ±0.33GPa; microwave-specific resin, 3.01 ±0.20GPa; and microwave-option resin, 2.63 ±0.04GPa. After load cycling, the mean flexural modulus was conventionally processed resin, 2.34 ±0.32GPa; microwave-specific resin, 2.69 ±0.20GPa; and microwave-option resin, 1.96 ±0.11GPa. The initial flexural strength was conventionally processed resin, 77.6 ±11.0MPa; microwave-specific resin, 83.6 ±3.5MPa; and microwave-option resin, 78.9 ±2.6MPa. After load cycling, the mean flexural strength was conventionally processed resin, 68.7 ±9.0MPa; microwave-specific resin, 73.3 ±3.3MPa; and microwave-option resin, 65.5 ±3.5MPa. Resin and loading state significantly affected the stiffness and strength (P<.01); the interaction resin×state was not significant (P≥.558). Microwave-polymerized denture base acrylic resins were comparable in stiffness and strength with conventionally processed acrylic resin. All acrylic resins decreased in stiffness and strength after load cycling. The microwave-specific resin was significantly stiffer and stronger than the other denture base acrylic resins, initially and after 120 000 load cycles.

Polymerization Cycle and Occlusal Vertical Dimension of Complete Dentures: Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to assess the influence of the polymerization cycle on the occlusal vertical dimension (OVD) of complete dentures. This review was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The PICO (Population, Intervention, Comparison, Outcome) question evaluated was “Does the microwave polymerization cycle influence the occlusal vertical dimension of complete dentures when compared to conventional water bath polymerization?”. The literature search was conducted in the PubMed/MEDLINE, Web of Science, and Scopus databases for relevant articles published up to March 2023. In vitro studies involving OVD measurement from complete dentures polymerized with different polymerization methods were included. The risk of bias was analyzed using the Critical Appraisal Checklist for Quasi-Experimental Studies (non-randomized experimental studies) from the Joanna Briggs Institute (JBI). The meta-analysis was based on the inverse variance (IV) methods with mean difference (MD) for OVD evaluation between techniques. Five articles were included in the qualitative and quantitative analysis. A total of 222 complete dentures were evaluated. In the polymerization cycles, microwave cycles with 90 W to 810 W between 3-5 minutes and conventional water bath cycles between 9-12 hours (long cycles) and 3-4 hours (short cycles) were used. In a quantitative analysis of polymerization methods, no statistically significant difference was found between water bath and microwave techniques [p = 0.99; MD: -0.00; CI = -0,26-0,26]. The current meta-analysis can be concluded that both techniques can be used to polymerization of complete dentures without significant clinical changes in the OVD.

Effect of microwave polymerization on the thermomechanical and surface properties of ocular prosthetic acrylic resins.

Polymerization conditions affect the physical-mechanical properties of acrylic resins used for craniofacial prostheses. The aim of this study was to evaluate the effect of microwave polymerization on the thermomechanical properties and surface morphology of ocular prostheses fabricated with polymethyl methacrylate (PMMA). PMMA discs were polymerized with microwave energy and with conventional heat polymerization (CHP) method. Ocular prostheses were fabricated to determine whether there were changes according to the polymerization method. The surface morphology and roughness were observed under SEM and AFM. The Vickers Hardness number (VHN) and flexural strength were measured. Thermal properties were evaluated with TGA/DSC, and chemical composition with FTIR. The PMMA acrylic resin polymerized with microwave energy showed a smooth surface with some relief areas. In the internal surface of the ocular prosthesis with microwave energy the PMMA is more compact. The mean roughness values were higher and statistically significant with CHP (P <0.05), while the surface hardness and flexural strength were higher with microwave energy (P <0.05). There were no changes in the calorimetry with either method, TGA showed an exothermic peak around 120°C with CHP method. PMMA polymerized with microwave energy improved the mechanical and surface properties of the ocular prostheses.

Novel and Facile Synthesis of Biodegradable Plastic Films from Cornmeal by Using the Microwave Polymerization Technique

Millions of tons of plastic are produced annually, but a major portion of plastic waste remains unrecycled. The uncycled plastic ultimately becomes a major source of solid trash and releases a variety of chemicals into our environment which can adversely affect the human health and marine life. In this study, a novel approach has been opted to synthesize a biodegradable plastic by using the microwave polymerization technique. In this novel approach, raw material (cornmeal), plasticizer (glycerin), and additive (vinegar) have been combined together to fabricate biodegradable plastic films from the microwave polymerization method. A number of rheological properties such as shear stress (Pa), shear rate (1/s), strain, and viscosity (Pa.s) of newly synthesized plastic were studied. These properties confirmed the presence of a shear thinning effect in the biodegradable plastic films on the basis of flow behavior of cornmeal. In order to check the water uptake ability and biodegradability of the cornmeal-based plastic films, water uptake and biodegradation tests were carried out. The fabricated films were neat, thin, and chewable and demonstrate promising characteristics. Therefore, these synthesized films can potentially become a suitable candidate in the packaging industry.

Imprinted modified S-scheme heterojunction with high selectivity for inhibiting CdS photocorrosion by coating with poly-o-phenylenediamine

Imprinted modified poly-o-phenylenediamine (POPD)/CdS S-scheme heterojunction (IM-POPD/CdS) was synthesized by microwave polymerization method, which showed excellent CdS photocorrosion resistance and photocatalytic degradation performance towards danofloxacin mesylate (DFM). Interestingly, owing to the presence of imprinted cavities on IM-POPD/CdS, IM-POPD/CdS can selectively adsorb and degrade DFM. IM-POPD/CdS exhibited a good orientation degradation ability in different water environments. More importantly, due to the coating of the imprinted modified POPD layer and the consumption of h+ in the CdS valence band by e- on the POPD, the photocorrosion of CdS is greatly inhibited, and its secondary pollution is reduced. This study provides a new idea for photocorrosion resistant functional heterojunction materials and an exemplary way for the effective directional degradation of target pollutants.

Aqueous-phase synthesis of heterojunction molecular imprinted photocatalytic nanoreactor via stable interaction forces for improved selectivity and photocatalytic property

Common molecular imprinted photocatalysts are usually prepared in highly toxic organic solvent medium, which will be disturbed by water molecules and swelling differences when used for selective recognition in the aqueous phase. In this study, an ionic liquid (IL) was used as the functional monomer and functionalized P25@IL heterojunction molecular imprinted photocatalytic nanoreactor, referred to as imprinted P25@IL nanoreactor, were prepared via the aqueous-phase microwave polymerization strategy. Imidazole-based IL cations can provide π electron clouds, and side chains are easily functionalized and modified, resulting in strong interactions such as π-π and ion dipoles being formed between IL and levofloxacin hydrochloride (LEV), which can overcome the interference of water molecules and achieve better selective adsorption and degradation of LEV in aqueous medium. The selectivity coefficient of imprinted P25@IL nanoreactor relative to P25 and functionalized P25@IL heterojunction molecular non-imprinted photocatalyst (non-imprinted P25@IL photocatalyst) were 2.69 and 2.26, respectively. More importantly, with the formation of IL-P25 heterojunction and surface imprinted layer, the photocatalytic performance of imprinted P25@IL nanoreactor was 2.33 times higher than that of P25. Our findings offer a novel approach to the synthesis of water-soluble functional monomers and the aqueous-phase synthesis of molecular imprinted photocatalytic materials.

Rapid Microwave Polymerization of Porous Nanocomposites with Piezoresistive Sensing Function.

In this paper, polydimethylsiloxane (PDMS) and multi-walled carbon nanotube (MWCNT) nanocomposites with piezoresistive sensing function were fabricated using microwave irradiation. The effects of precuring time on the mechanical and electrical properties of nanocomposites were investigated. The increased viscosity and possible nanofiller re-agglomeration during the precuring process caused decreased microwave absorption, resulting in extended curing times, and decreased porosity and electrical conductivity in the cured nanocomposites. The porosity generated during the microwave-curing process was investigated with a scanning electron microscope (SEM) and density measurements. Increased loadings of MWCNTs resulted in shortened curing times and an increased number of small well-dispersed closed-cell pores. The mechanical properties of the synthesized nanocomposites including stress–strain behaviors and Young’s Modulus were examined. Experimental results demonstrated that the synthesized nanocomposites with 2.5 wt. % MWCNTs achieved the highest piezoresistive sensitivity with an average gauge factor of 7.9 at 10% applied strain. The piezoresistive responses of these nanocomposites were characterized under compressive loads at various maximum strains, loading rates, and under viscoelastic stress relaxation conditions. The 2.5 wt. % nanocomposite was successfully used in an application as a skin-attachable compression sensor for human motion detection including squeezing a golf ball.

Selective photocatalytic degradation of tetracycline by metal-free heterojunction surface imprinted photocatalyst based on magnetic fly ash

The metal-free heterojunction surface imprinted photocatalyst based on magnetic fly ash (PPy@g-C3N4@MFA surface imprinted photocatalyst, PGM-SIP) was synthesized by microwave polymerization and surface imprinting technique. Additionally, the polypyrrole (PPy) and g-C3N4 can form metal-free heterojunction structure. More importantly, the PGM-SIP can selectivity recognize and degrade tetracycline due to the presence of plenty of three-dimensional imprinted cavities on PGM-SIP, and the selectivity coefficient of PGM-SIP relative to g-C3N4@MFA, PPy@g-C3N4@MFA and non-imprinted photocatalyst was 1.587, 1.756 and 2.580, respectively. Therefore, this work offered an exemplary strategy for selective photodegradation of target antibiotic.

The effect of stainable drinks followed by simulated brushing on the roughness and stainability of acrylic resins polymerized with different cycles

Statement of problemNo information is available on roughness and stainability of acrylic resins polymerized by experimental microwave cycles after immersion in stainable liquids and simulated brushing. PurposeThe purpose of this in vitro study was to evaluate the effect of stainable drinks and brushing on roughness and stainability of acrylic resins (Vipi Cril [CA] and Vipi Wave [MA]) polymerized with different cycles. Material and methodsCA and MA specimens (n=5; diameter, 20 mm; thickness, 3 mm) were made using 4 methods recommended by the manufacturer (water bath polymerization and microwave polymerization cycles) and experimental at 550 W or 650 W for 3 or 5 minutes (M550/3 and M650/5), respectively. After storage in distilled water at 37°C for 48 hours (T0), the specimens were stored in water, coffee, or red wine (37°C) for 36 days with simulated brushing (54 000 cycles, T1). Roughness (Ra) and stainability (ΔE/National Bureau of Standards) were measured at T0 and T1. Roughness and stainability data were analyzed by 3-way repeated measures and 2-way ANOVA, respectively, followed by the Bonferroni test (α=.05). ResultsAfter storing in coffee and brushing, CA showed the highest (M550/3=2.33 ±0.72 μm) and the lowest roughness (water bath polymerization=1.22 ±0.58 μm), whereas roughness of MA specimens processed by M650/5 increased (1.57 ±0.59 μm). Storing in wine and brushing increased roughness (1.75 ±0.32 μm) in the M550/3 group. No staining was observed on MA after brushing regardless of the polymerization cycle. All values were acceptable (ΔE≤3.3), except for MA (microwave polymerization), which showed National Bureau of Standards=4.49 (appreciable change) after storing in wine and brushing. ConclusionsA slight increase in material roughness was observed after staining and brushing. Only MA polymerized following manufacturer cycles showed relevant stainability after immersion in wine and brushing.

Knoop microhardness of conventional and microwaved denture base acrylic resins.

Microwave polymerization reduces the time of acrylic resin processing, but it is important to select a proper cycle to avoid overheating, porosity, and impairment to the materials' properties. To evaluate the microhardness of conventional (Vipi Cril-VC) and microwaved (Vipi Wave-VW) acrylic resins after microwave polymerization cycles and the cycles recommended by the manufacturer. It was also evaluated the effect of thermocycling on the microhardness of these materials. Specimens (n = 10) were made: 1. WB (water-bath recommended for VC polymerization); 2. M630/25 (10 min at 270 W; 5 min at 0 W; 10 min at 360 W: recommended for VW polymerization); 3. M550/3 (3 min at 550 W); and 4. M650/5 (5 min at 650 W). After 48 h in distilled water at 37°C, specimens were subjected to Knoop test under 25 g during 5 s. The same specimens were submitted to thermocycling (5,000 cycles; 5°C and 55°C; 60 s) and the microhardness was again measured. The results were analyzed by repeated measures one-way analysis of variance/Bonferroni for each material (α = 0.05). For both materials, no difference was obtained for groups polymerized using the cycles recommended by the manufacturer (VC = 19.8 ± 0.9 KHN; VW = 21.0 ± 1.6 KHN) and M650/5 (VC = 19.9 ± 1.5 KHN; VW = 20.9 ± 0.8 KHN). After thermocycling, microhardness decreased in experimental cycles for VC (M550/3 = 17.0 ± 1.9 to 14.6 ± 1.2 KHN; M650/5 = 19.9 ± 1.5 to 17.8 ± 0.8 KHN) and in all microwave cycles for VW (M630/25 = 21.0 ± 1.6 to 18.3 ± 0.9 KHN; M550/3 = 17.5 ± 3.0 to 15.7 ± 2.0 KHN; M650/5 = 20.9 ± 0.8 to 18.2 ± 2.0 KHN) (P = 0.000). The lowest hardness was observed for both resins processed by M550/3 (P = 0.001). Both materials could be polymerized in microwave during 5 min showing hardness similar to the cycles recommended by the manufacturer. Thermocycling did not decrease the hardness of VC polymerized with both cycles recommended by the manufacturer and VW polymerized with the water-bath conventional cycle.

Porosity, water sorption and solubility of denture base acrylic resins polymerized conventionally or in microwave.

The proper selection of polymerization cycle is important to prevent overheating of the monomer that could cause degradation, porosity and, consequently, deleterious effects on the denture base properties.ObjectiveThis study evaluated the porosity, water sorption and solubility of acrylic resins (Vipi Cril-VC and Vipi Wave-VW) after conventional or microwave polymerization cycles.Material and MethodsSpecimens (n = 10) were made and cured: 1-WB = 65°C during 90 min + boiling during 90 min (VC cycle - control group); 2-M25 = 10 min at 270 W + 5 min at 0 W + 10 min at 360 W (VW cycle); 3-M3 = 3 min at 550 W; and 4-M5 = 5 min at 650 W. Afterward, they were polished and dried in a dessicator until a constant mass was reached. Specimens were then immersed in distilled water at 37°C and weighed regularly until a constant mass was achieved. For porosity, an additional weight was made with the specimen immediately immersed in distilled water. For water sorption and solubility, the specimens were dried again until equilibrium was reached. Data were submitted to 2 way-ANOVA and Tukey HSD (α=0.05).ResultsPorosity mean values below 1.52% with no significant difference among groups for both materials were observed. Resins showed water sorption and solubility values without a significant difference. However, there was a significant difference among groups for these both properties (P<0.013). The highest sorption (2.43%) and solubility (0.13%) values were obtained for WB and M3, respectively.ConclusionsThe conventional acrylic resin could be polymerized in a microwave since both the materials showed similar performance in the evaluated properties. Shorter microwave cycles could be used for both the materials without any detectable increase in volume porosity.

Hybridization of Al2O3 microspheres and acrylic ester resins as a synergistic absorbent for selective oil and organic solvent absorption

In this study, we have focused on the synthesis, characterization, and oil absorption properties of Al2O3 microspheres/acrylic ester resin (AER) hybrids. The Al2O3 microspheres are prepared by a combined hydrothermal and sintering processes, followed by surface modification with silane coupling agent (KH 570). The Al2O3 microspheres/AER hybrids with a rough surface are synthesized by a microwave polymerization route by using modified Al2O3 microspheres as modifiers. In this hybrid materials system, the Al2O3 microspheres with porous structures may provide fast oil absorption due to the low oils absorption energy and short diffusion lengths. The resin hybrids exhibited reversible oils and organic solvents adsorption with maximum absorption capacities up to 29.85 g/g. This study suggests potential environmental advantage in using metal oxide microspheres in improving the oil absorption properties of oil‐absorbing resins as absorbents for recovering oil and organic solvent from water.

Effect of Surface Treatments and Adhesive Materials on the Shear Bond Strength of Artificial Denture Teeth to Denture Base Resins

The purpose of the current study was intended to evaluate the effect of different surface modifications and different adhesive materials on the shear bond strength of artificial teeth to heat-polymerized and thermoplastic denture base materials using different repair techniques. Forty cross-linked artificial teeth used to construct different types of acrylic based denture prosthesis were selected to be bonded to two types of denture base materials, heat-polymerized acrylic resin denture base material, and thermoplastic acrylic resin denture base material. The specimens were divided into four subgroups according to the repair technique and adhesive material used. The base surfaces of all acrylic teeth then were moistened with monomer prior to bonding to the denture base specimens. Then, the specimens were tested using Universal Testing Machine for shear bond strength. The results were analyzed by using two-way analysis of variance (ANOVA) statistical analysis and multiple comparison tests, α ≤ 0.05. The effect of the types of denture base materials vs the surface conditioning methods displayed a statistically significant difference. This study concluded that monomer surface treatment of the bonded surface of artificial denture teeth and the use of cyanoacrylate adhesive followed by additional microwave polymerization displayed better shear bond strength when compared with other repair techniques. Artificial teeth debonding from their denture bases is a common complication in dental practice. The current study evaluates different repairing techniques. Within the limitation of this study, the use of cyanoacrylate adhesive in combination with microwave polymerization is one of the best techniques of repairing denture teeth debonding.

Facile microwave synthesis of a Z-scheme imprinted ZnFe2O4/Ag/PEDOT with the specific recognition ability towards improving photocatalytic activity and selectivity for tetracycline

The Z-scheme imprinted ZnFe2O4/Ag/PEDOT was synthesized by the microwave polymerization method and surface imprinting technique, which possessed good partial hollow spherical structure, good light response ability, good magnetic separation performance, good photocatalytic stability and reproducibility. More importantly, due to the introduction of Ag/PEDOT into the surface imprinted layer, Z-scheme structure was formed to enhance the photocatalytic activity based on Ag acted as the mediator, meanwhile, owing to the existence of the imprinted cavity in the surface imprinted layer, the selectivity had been significantly improved, in a word, the as-prepared Z-scheme imprinted ZnFe2O4/Ag/PEDOT achieved the goal for simultaneously improving the photocatalytic activity and selectivity. Z-scheme imprinted ZnFe2O4/Ag/PEDOT possessed the highest photodegradation rate (71.77%) for degradation of tetracycline under the simulated sunlight irradiation of 120 min, which was approximately 4.74 times to that of ZnFe2O4, 1.42 times to that of Ag/PEDOT and 1.31 times to that of non-imprinted ZnFe2O4/Ag/PEDOT, respectively. And the coefficient of selectivity of Z-scheme imprinted ZnFe2O4/Ag/PEDOT relative to ZnFe2O4, Ag/PEDOT, non-imprinted ZnFe2O4/Ag/PEDOT was 1.84, 1.82, 1.79 in the single antibiotic solution and 1.78, 1.75, 1.67 in the binary antibiotic solution, respectively. This work provided a new synthesis strategy for the imprinted photocatalysts and also provided a new idea for the treatment of specific pollutants in the water environment.

Enhancement of oil absorption properties of acrylic ester resin hybridized with well‐organized sea urchin‐like MnO2

Acrylic ester resin (AER) is a promising oil‐absorbing material for oils and organic solvents absorption because it exhibits high oil retention ability, good swelling properties, and reusability while also being inexpensive, large‐scale production, and environmentally benign. However, the AER is not fully utilized owing to its low oil absorption capacity and slow oil absorption rate. In this work, we combine porous structures of MnO2 and swelling properties of AER and design a novel route to fabricate sea urchin‐like MnO2/AER hybrids. In this route, the sea urchin‐like MnO2 was prepared by a facile hydrothermal method in acidic media. The sea urchin‐like MnO2/AER hybrids with different wt% were synthesized by a microwave polymerization route. The resin hybrids exhibited very rough surfaces, which are beneficial for organic molecules absorption and diffusion into the interiors of materials. The resin hybrids can remove oils and organic solvents from water with high selectivity and absorption capacity, and can absorb not only floating oil but also heavy organic solvents underwater. The maximum absorption capacity of resin hybrids was found at the MnO2 content of 3%, and maximum absorption capacity up to 32.5 times of their own weight, higher than that of the pure AER. The performances were mainly attributed to the unique porous structure of MnO2 and swelling properties of AER, indicating the potential application of such oil‐absorbing resins to introduce the porous inorganic materials for developing new oils and organic solvents absorbent for removal of organic pollutants from the wastewater. POLYM. COMPOS., 39:4041–4049, 2018. © 2017 Society of Plastics Engineers

Synthesis of MnO2/poly(n-butylacrylate-co-butyl methacrylate-co-methyl methacrylate) hybrid resins for efficient oils and organic solvents absorption

Oil-absorbing materials with three-dimensional network structure are being actively investigated due to their application in the treatment of oil spills and chemical leakage which result from their controllable porous structures and swelling properties. In this work, the oil-absorbing MnO2/poly(n-butylacrylate-co-butyl methacrylate-co-methyl methacrylate) resin composite (MnO2/p(BA-co-BMA-co-MMA)) was synthesized by using a combined hydrothermal method and microwave polymerization method, and was successfully applied to absorb oils and organic solvents. In this synthesis, the MnO2 hollow spheres were prepared via a simple hydrothermal method and modified by γ-methacryloxypropyl trimethoxysilane (KH-570) under microwave irradiation. Then, the MnO2/p(BA-co-BMA-co-MMA) hybrid resin with good oil absorption capacity and excellent recyclability were synthesized through suspension polymerization by a microwave polymerization route. The as-prepared samples were characterized by Fourier transmission infrared spectroscopy (FT-IR), X-ray diffraction (XRD), contact angle, scanning electron microscopy (SEM), etc. The as-prepared porous-structured MnO2 that are comprised of individual microrods possess self-organized shaggy, ball-shaped architectures with sizes ranging from 2 to 4 μm. In order to obtain the hydrophobic surfaces, the surfaces of MnO2 microspheres were chemically modified by KH-570 under microwave irradiation. And the surface of modified MnO2 show high repellency towards water with a water contact angle of 135°. Moreover, the absorption properties of the MnO2/p(BA-co-BMA-co-MMA) hybrid resins were tested in this work. The results indicated that the oil absorption properties were strongly influenced by the content of MnO2 hollow spheres. Furthermore, the MnO2/p(BA-co-BMA-co-MMA) hybrid resin has a maximum absorption capacities of 34.56 g*g−1, 31.82 g*g−1 and 25.89 g*g−1 for the absorption of chloroform, carbon tetrachloride and toluene respectively and could selectively remove oils from water which is promising for their potential applications in oil spill cleanup.

Comparison of the flexural strength of polymethyl methacrylate resin reinforced with multiwalled carbon nanotubes and processed by conventional water bath technique and microwave polymerization.

Purpose:This in vitro study was done to compare the flexural strength of polymethyl methacrylate resin reinforced with multiwalled carbon nanotubes (MWCNTs) and processed by conventional water bath technique and using microwave energy.Materials and Methods:A total of 180 acrylic resin specimens measuring 65 mm × 10 mm × 2.5 mm were fabricated, with conventional water bath groups and microwave group having ninety specimens each. Ninety specimens were divided into thirty specimens as control and subgroups containing 0.025% MWCNTs and 0.050% MWCNTs with thirty specimens each. The specimens were tested for flexural strength by three-point bending test on universal testing machine. The statistical analysis was done using Student's t-test and one-way analysis of variance, and the intercomparison between each group was done using Tukey's post hoc analysis.Results:The mean flexural strength of specimens cured by water bath technique was 95.563 MPa and microwave technique was 118.416 MPa. Control Group B possesses highly significant increase in flexural strength than Control Group A with P < 0.01. Unpaired Student's t-test showed that Subgroup B1 and Subgroup B2 possess highly significant increase in flexural strength than Subgroup A1and Subgroup A2.Conclusion:Heat polymerized denture base resin with and without reinforcement of MWCNTs and polymerized by microwave technique possess higher flexural strength than heat polymerized fiber reinforced denture resin polymerized by water bath technique. MWCNTs could be used as an effective reinforcement material for denture base resin polymerized by either water bath technique or microwave energy.

Allergic effects of the residual monomer used in denture base acrylic resins.

Denture base resins are extensively used in dentistry for a variety of purposes. These materials can be classified as chemical, heat, light, and microwave polymerization materials depending upon the factor which starts the polymerization reaction. Their applications include use during denture base construction, relining existing dentures, and for fabrication of orthodontic removable appliances. There have been increased concerns regarding the safe clinical application of these materials as their biodegradation in the oral environment leads to harmful effects. Along with local side effects, the materials have certain occupational hazards, and numerous studies can be found in the literature mentioning those. The purpose of this article is to outline the cytotoxic consequences of denture base acrylic resins and clinical recommendations for their use.

Effect of conventional water-bath and experimental microwave polymerization cycles on the flexural properties of denture base acrylic resins.

The effect of polymerization cycles on flexural properties of conventional (Vipi Cril(®)-VC) or microwave-processed (Vipi Wave(®)-VW) denture base acrylic resins was evaluated. Specimens (n=10) were submitted to the cycles: WB=65ºC for 1 h+1 h boiling water (VC cycle); M630/25=10 min at 270 W+5 min at 0 W+10 min at 360 W (VW cycle); M650/5=5 min at 650 W; M700/4=4 min at 700 W; and M550/3=3 min at 550 W. Specimens were submitted to a three-point bending test at 5 mm/min until fracture. Flexural strength (MPa) and elastic modulus (GPa) data were analyzed by 2-way ANOVA/Tukey HSD (α=0.05). Overall, VC showed higher values than VW. The results obtained with microwave polymerization did not differ from those obtained with water-bath for both acrylic resins. The results observed when polymerization cycles using medium power and shorter time were used did not differ from those when manufacturer's recommended microwave cycle was applied. Conventional VC might be microwave-processed without compromising its flexural properties.

Synthesis of Mn2O3/poly(styrene-co-butyl methacrylate) resin composites and their oil-absorbing properties

This paper reports the synthesis of Mn2O3/poly(styrene-co-butyl methacrylate) resin composites by using a combined biotemplate technology and microwave polymerization method, as well as their application in oil absorption.