Heat Of Polymerization Research Articles

Boosting of photocatalytic degradation of Malachite green dye on facile synthesized highly active Ca@TiO2@g-C3N4 photocatalyst: Photocatalytic mechanism and kinetics

The Ca@TiO2@g-C3N4 nanocomposite was synthesized using non-precious components via heat polymerization followed by an ultrasonic power technique. The nanocomposite was extensively characterized. The X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) investigations unequivocally demonstrated the successful synthesis of the Ca@TiO2@g-C3N4 nanostructures. By account of its small particle size of 6.1081 nm, narrow band gap energy of 2.82 eV, and visible light activity, it was able to photodegrade MG dye in an efficient manner, achieving a 99.9 % degradation rate. The photoluminescence measurement demonstrated efficient separation and transfer of charge carriers. The ternary photocatalyst’s activity can be attributed to the production of a S-scheme heterojunction at the interfaces of TiO2@g-C3N4, the generation of defects such as Ti3+ and Ovs through the surface interaction of Ca with TiO2, and the enlarged surface area of the photocatalyst. The ternary Ca@TiO2@g-C3N4 nanostructures demonstrated superior photodegradation of MG dye in comparison to pure g-C3N4 and binary TiO2@g-C3N4. A viable mechanism is also shown through active species trapping experiments using different scavengers, demonstrating that the photogenerated h+ and O2− are vital in the photodegradation reaction under visible light irradiation. Furthermore, the catalyst’s potential for industrial applications is enhanced by its utilization of inexpensive initial ingredients, straightforward synthesis process, and ability to harness solar light.

Comparison of the Antimicrobial Efficacy of Conventional Versus Chitosan Re-inforced Heat-Polymerized Polymethylmethacrylate Dental Material: An In Vitro Study.

Polymethylmethacrylate (PMMA) is widely used in the fabrication of dentures due to its aesthetic appeal and mechanical strength. However, PMMA's susceptibility to microbial colonization often leads to oral infections such as denture stomatitis. Enhancing the antimicrobial properties of denture materials is crucial for improving patient outcomes.Chitosan, a natural biopolymer, possesses inherent antimicrobial properties and could potentially enhance the microbial resistance of PMMA. This study has investigated thepotential of chitosan-reinforced heat-polymerized PMMA denture material to reduce microbial colonization. The aim of the study was to evaluate and assess the anti-bacterial and antifungal properties of chitosan-reinforced heat-polymerized PMMA with conventional heat-polymerized PMMA Materials and methods:Chitosan-reinforced PMMA samples were fabricated with varying chitosan concentrations (0% control, 5%, 10%, and 15% by weight). The fabrication involved mixing chitosan powder with PMMA powder, adding monomer liquid, followed by mixing, packing, and curing using the conventional heat polymerization technique. The antimicrobial efficacy was assessed in vitro using two common oral pathogens: Streptococcus mutans and Candida albicans. Blood agar plates were used for S. mutans and Sabouraud agar plates were used for C. albicans. Each sample was placed on the respective agar plates inoculated with a standardized microbial suspension and incubated at 37°C for 24 hours. The number of colony-forming units (CFUs) was counted to quantify microbial growth. Statistical analyses, including linear regression analysis, one-way ANOVA test, and Pearson correlation were performed to evaluate the relationship between chitosan concentration and antimicrobial efficacy. The p-value was calculated to determine the statistical significance of the results. The chitosan-reinforced PMMA samples showed significantly greater antimicrobial efficacy compared to the conventional PMMA samples. The CFU counts for both S. mutans and C. albicans decreased with increasing chitosan concentration. Linear regression analysis indicated a strong negative correlation between chitosan concentration and CFU counts, with Pearson correlation coefficients of -0.97 for S. mutans and -0.98 for C. albicans. ANOVA analysis revealed a statistically significant difference in antimicrobial efficacy across different chitosan concentrations (p < 0.001). Incorporating chitosan into heat-polymerized PMMA significantly enhances its antimicrobial properties against S. mutans and C. albicans. The antimicrobial efficacy improves with higher concentrations of chitosan, with the 15% chitosan-reinforced samples showing the most substantial reduction in microbial growth. These results suggest that chitosan-reinforced PMMA dentures could be a superior alternative to conventional PMMA dentures, potentially reducing denture-related infections and improving oral health outcomes for denture wearers.

Study on the dynamic heating polymerization of PA MXD6: From thermal analysis to efficient polymerization

Optimizing a practical polymerization strategy for poly(m-xylylene adipamide) (PA MXD6) requires regulating the high-temperature residence time and preventing the solidification of the reaction mixture. Dynamic heating strategies have shown promise in addressing this issue. However, conventional polycondensation kinetics are not optimal for characterizing nonisothermal processes due to continuous changes in the reactant state. This study employed thermal analysis as a continuous monitoring method to comprehensively investigate the effects of pressure, temperature, and diffusion on polymerization. The results indicate that high heating rates lead to faster reaction rates, as evidenced by the evolution of the kinetic parameters throughout the reaction process. Nevertheless, excessively high heating rates increase the solidification risk. To resolve this contradiction, a low-rate heating process with pressure was developed for efficient polymerization and scale-up, resulting in superior products. This study provides new insights into polyamide polymerization and offers practical guidelines for enhancing polymerization efficiency and process stability.

Efficient Visible‐Light‐Driven Aromatic Alcohol Oxidation Using PI‐TiO2 Composite Photocatalyst

AbstractSynthesizing fine chemicals and valuable pharmaceutical intermediates through selective catalytic oxidation of alcohols is indispensable and crucial. However, the conventional methods of alcohol oxidation have inevitable drawbacks, including harsh reaction conditions and environmental pollution. Thus, it is imperative to develop efficient catalytic oxidation systems for alcohols. Herein, we successfully synthesized a 15 wt %PI‐TiO2 composite by a one‐step solid‐state heating polymerization technique. This catalyst exhibits excellent responsiveness to visible light and demonstrates remarkable catalytic activity. Furthermore, TEMPO was introduced as a cocatalyst to construct a PI‐TiO2/TEMPO/O2 system for the catalytic oxidation of alcohols. In comparison to the individual effects of PI or TiO2, this system showcases improved catalytic activity and broader substrate applicability. As a result, the conversion efficiency of benzyl alcohol increases by 3.44 times and 2.26 times, respectively. This research not only introduces a novel approach for preparing visible light‐active PI‐TiO2 catalysts but also indicates the significance of establishing an efficient electron transfer process in alcohol catalytic oxidation.

Effects of Combinations of Hydrogen Peroxide and Vinegar in Different Ratios on the Surface Roughness of Heat-Cure Denture Base Acrylic Resin

Background: Complete dentures are at high risk of contamination, and their disinfection is imperative to prevent cross-contamination. Also, chemical disinfecting agents can effectively eliminate microorganisms. This study aimed to assess the effect of combinations of hydrogen peroxide (HP) and vinegar in different ratios on the surface roughness of heat-cure denture base acrylic resin. Methods: This in vitro, experimental study evaluated 40 heat-cure acrylic resin specimens that were flasked and heated at 70 ° C for 9 hours for heat polymerization. The acrylic specimens were cut into small cubic pieces measuring 20×20×3 mm using a cutting machine and polished with metallographic abrasive paper. The specimens were randomized into 4 groups of control (artificial saliva) and HP and vinegar in 1:1, 1:3, and 3:1 ratios (three experimental groups). Then, they were immersed in the respective solutions for 8 hours/day for one month. Their surface roughness (Ra) was measured before and after immersion by a profilometer. The data were analyzed using a one-way analysis of variance (α=0.05). Results: The immersion of acrylic specimens in HP+vinegar in 1:1 and 1:3 ratios did not cause a significant change in their surface roughness (P&gt;0.05). However, the surface roughness significantly decreased after immersion in HP+vinegar in a 3:1 ratio (P=0.032). Despite the reduction in the surface roughness of specimens in the 3:1 group, the difference in surface roughness was not significant among the four groups after immersion (P&gt;0.05). Conclusion: Combinations of HP and vinegar in different ratios appear to be suitable for cleaning removable dentures due to their insignificant effects on the surface roughness of acrylic resin.

B and N Co-doped carbon dots for the ratiometric fluorescence detection of riboflavin and information security with room temperature phosphorescence

Matrix-free room temperature phosphorescence (RTP) materials have generated considerable interest in sensing, anti-counterfeiting and bioimaging due to long lifetime and large Stokes shift. However, spin-forbidden transition and non-radiative transition make RTP challenging to implement. In this work, matrix-free RTP carbon dots (CDs) co-doped with boron and nitrogen were prepared through the microwave-assisted strategy. The CDs realize RTP without any protective matrix. This may be attributed to the stable and rigid structure formed during the heating polymerization process, which can protect the triplet excited state from being quenched by oxygen and water in the air environment. The fluorescence and phosphorescence emission wavelength of the as-prepared CDs were observed at 532 nm and 596 nm with the excitation wavelength of 476 nm and 514 nm, respectively, showing a long afterglow lifetime of 735.3 ms. Nitrogen doping has a crucial effect on the luminescence of RTP, and the increase of nitrogen content facilitates the n-π* transition and improve the efficiency of intersystem crossing (ISC). Importantly, the ratiometric fluorescence method for determining riboflavin has been established based on the Förster resonance energy transfer (FRET) between the CDs (Donor) and riboflavin (Acceptor), with a linear relationship in the range of 9.52–85.71 μM and the limit of detection (LOD) of 19.9 nM. Additionally, the phosphorescent property of the CDs was exploited to demonstrate the potential applications in the field of information encryption.

Evaluation and Comparison of Impact Strength and Transverse Strength of Heat Polymerized Polymethylmethacrylate (PMMA) Denture Base Resin Repaired Using Heat Polymerizied PMMA Denture Base Resin, Auto-Polymerized PMMA Resin and A New Light Polymerizied Denture Resin: An In Vitro Study.

Repaired denture prosthesisdemands adequate transverse and impact strength. A new repairdenture base resin- "Lukafix" require to fulfil these criteria. This study evaluates and compares the transverse and impact strength of heat polymerizing, auto polymerizing and LUKAfix denture resin. 20 specimens were control(without repair), and other were test specimens which were fractured and repaired with heat polymerized PMMA resin, chemically polymerized PMMA resin and LUKAfix light polymerizing denture resin. Each group wasdivided in two subgroups. Subgroup A was subjected to transverse strength test and subgroup B to impact strength test. One way ANOVA was used to identify the mean difference among the four groups. Post-Hoc-Bonferroni was done to observe the difference between the groups. Maximum transverse strength was observed in specimens repaired with heat polymerized (48.33 ± 9.19) and least in LUKAfix denture resin (6.56 ± 1.15). Also, impact strength was maximum for heat polymerized (3.64 ± 0.41) followed by LUKAfix denture resin (2.34 ± 0.44). Repair with LUKAfix denture resin resulted inferior transverse and impact strength as compared to heat polymerized PMMA resin.

The Effect Of Surface Treatment And Thermocycling On Bond Strength Between Silicon Soft Denture Lining And Acrylic Resin Denture Base

Introduction: Silicon Soft Denture Liner (SDL) is often used along with heat polymerization acrylic resin (PMMA) as an obturator material because it can cover the undercut area in a broad defect for long term and painlessly. Despite that, silicon SDL and PMMA have different molecular structures so that they have a low bond strength. Long-term use can also affect the bond strength, so there is a need to increase the bond strength between PMMA and SDL. A method to increase the bond strength is surface treatment. This study is conducted to determine the effect of surface treatment and thermocycling on the bond strength of PMMA and Silicon SDL. Methods: The study used 40 samples (8 groups) divided into 4 groups based on the surface treatments, namely no surface treatment, sandblast, adhesive primer and combination, and further divided into two groups of thermocycling and without thermocycling treatment. The bond strength between PMMA and SDL was tested with tensile test by using Universal Testing Machine (UTM). Results: One-way ANOVA analysis showed there were significant differences of the bond strength among all groups (p &lt;0.05) where the adhesive primer showed the highest value in all treatment groups. Conclusion: There is an effect of surface treatment and thermocycling on the bond strength between the PMMA and SDL, where the adhesive primer as a surface treatment material shows the highest bond strength of all.

The Effect of Controlled Diabetic and Non-diabetic Saliva on Candida albicans Adherence to Heat Polymerized Acrylic Resin Discs

Background: Oral candidiasis is one of the most common infections in diabetic patients that may occur due to a decrease in salivary flow rate, alterations in the salivary composition, or both. This study aimed to investigate the effect of diabetic and non-diabetic saliva on Candida albicans adherence to the acrylic resin disc specimens, regardless of saliva volume. Methods: In this case-control study, the population consisted of 26 subjects in 2 groups (13 diabetic patients and 13 non-diabetic patients). In both groups, unstimulated whole saliva was collected. It was investigated for pH, salivary flow rate, and adhesion of C. albicans to polymethylmethacrylate disc. After preparing the polymethylmethacrylate discs, the samples were stored in diabetic saliva, non-diabetic saliva, and distilled water (negative control group) for 60 minutes at 37ºC. Then they were immersed in the yeast suspensions containing C. albicans and stained with gram stain. Yeast cells were counted using a light microscope. Results: The pH of unstimulated whole saliva in diabetic patients was significantly lower than in the control group. There was no significant difference between the flow rates of saliva in the two groups. Findings indicated that the adhesion of C. albicans to resin in diabetic saliva was higher than in non-diabetic saliva. Conclusion: This study showed the same amount of salivary flow rate in diabetic and non-diabetic individuals, lower pH, and higher Candida adherence to heat polymerization acrylic resin in the diabetic group.

Effects of Smokeless Tobacco on Color Stability and Surface Roughness of 3D-Printed, CAD/CAM-Milled, and Conventional Denture Base Materials: An In Vitro Study

Tobacco consumption in its different forms can affect the optical and surface properties of dental materials that are used in the oral cavity. Thus, the present study was conducted to evaluate the effects of two commercially available smokeless tobacco products on the color stability and surface roughness of denture base resins that were fabricated using three different techniques (CAD/CAM milling, 3D printing, and conventional heat polymerization). A total of 126 denture base resin specimens were fabricated using the three different manufacturing techniques (n = 42 each). Specimens from each group were further subdivided into three subgroups (n = 14 each) and immersed in three different immersion media (a khaini suspension, a tabbaq suspension, and artificial saliva). The differences in color and surface roughness were assessed according to data that were collected and statistically analyzed using SPSS version 24.0. The tabbaq smokeless tobacco was found to cause greatest changes in color and surface roughness; the effect was observed to be highest in the 3D-printed specimens followed by the conventional heat-polymerized and CAD/CAM milled specimens. The mean changes in color and surface roughness were the highest for the tabbaq smokeless tobacco followed by the khaini smokeless tobacco and the artificial saliva. Statistically significant (p-value < 0.05) differences were observed among all techniques and suspensions. We concluded that the mean changes in color and surface roughness were significantly higher for the 3D-printed dentures compared to the conventional heat-polymerized and CAD/CAM-milled dentures. Thus, the results of the present study strengthened the concept that tobacco in any form can lead to changes in the color and surface roughness of denture base materials.

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.

Investigation of the Interaction of Adipose-Derived Mesenchymal Stem Cells with ε-Polycaprolactone and Egg White Scaffolds

The development of three-dimensional (3D) cell culture models is becoming increasingly important due to their numerous advantages over conventional monolayer culture. This study aimed to examine the interaction of adipose tissue-derived mesenchymal stem cells (AD-MSCs) with scaffolds composed of ε-polycaprolactone (ε-PCL) and egg white. In our study, ε-PCL and egg white scaffolds were produced from their monomers by tin octoate catalyzed and heat polymerization, respectively. Characterization of ε-PCL was carried out by Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectrophotometry (FTIR), Proton Nuclear Magnetic Resonance (H-NMR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). AD-MSCs labeled with red fluorescent CellTracker CM-DiI were cultured on egg white and ε-PCL scaffolds for 12 days. Cell viability was determined using 3-(4.5-Dimethylthiazol-2yl)-2.5-diphenyltetrazolium bromide (MTT) and nitric oxide (NO) level was evaluated for toxicity. The results showed that the number of AD-MSCs in the egg white scaffold increased periodically for 12 days compared to the other groups. Although the number of AD-MSCs in the ε-PCL scaffold increased until day 6 of the culture, the number of cells started to decrease after day 6. These results were associated with the toxic effect of lactic acid release on cells resulting from the decomposition of ε-PCL scaffolds through catabolic reactions. Therefore, these results indicated that the egg white scaffold enhanced and maintained cell adhesion and cell viability more than the ε-Polycaprolactone scaffold and could be used as a scaffold in tissue engineering studies involving stem cells.

The effect of adding zirconium dioxide nanoparticle to acrylic denture base on porosity and candida albicans adhesion

Acrylic resin is the most common fabricated material for denture bases. ZrO2 nanoparticles can be used as filler to strengthen the physical properties and inhibit the adhesion of acrylic resins. This study aimed to examine the growth of Candida albicans and porosity in reinforced acrylic resin with Zirconium Dioxide (ZrO2) nanoparticles at 2.5% and 5% a concentration targeted for denture bases application. A laboratory experiment study included twenty-seven disc-shaped samples which were divided into three groups: group I acrylic resin without ZrO2 nanoparticles (control), group II acrylic resin with 2.5% ZrO2 nanoparticles, and group III with 5% ZrO2 nanoparticle acrylic resin. Samples were collected by heat polymerization while porosity observations were done using primo zeizs starr (Nikon YS100) microscope at 100x magnification. Dilution test was implemented to assess Candida albican growth. One-way ANOVA and Post Hoc LSD test statistical analysis were performed to evaluate the data (p&lt;0.05). The results indicated that the mean porosity values in the control group of 2.5% and 5% were 37.4 ± 3.5, 15.8 ± 3.3, 8.0 ± 2.0 respectively while the attachment of C. albicans was 0.832 ± 0.083, 0.536 ± 0.098, 0.218 ± 0.083. One-way ANOVA confirmed a significant effect (p&lt;0.05). Similarly, Post Hoc LSD test reported significant difference (p&lt;0.05). The results showed that acrylic resin reinforced with ZrO2 nanoparticles for heat-polymerized denture base effectively reduced porosity and C. albicans adhesion. Five percent of ZrO2 nanoparticle concentration presented greater porosity reduction compared to 2.5% ZrO2 and non-reinforced acrylic resin. Acrylic resin reinforced with ZrO2 nanoparticles in 2.5% and 5% concentration is fungistatic.

Hydrazine modified g-C3N4 with enhanced photocatalytic activity for degradation of indigo carmine

Polymeric graphitic carbon nitride (g-C3N4) was obtained from urea and modified by heat polymerization at 550 °C in the presence of hydrazine as a modifier agent. The influence of in-situ generated NH3 by hydrazine decomposition at different contents (0.5, 1, 1.5, and 2 mL) on the physicochemical properties and surface properties (water contact angle and point of zero charge) of the g-C3N4 were investigated. The modified g-C3N4 were analyzed by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, Fourier Transform Infrared, water contact angle, surface area, and the point of zero charge. The in-situ generated NH3 induced an evolution from nano-flakes to lamellar plate morphology depending on stacked interplanar. The influence of surface properties on the photocatalytic response of the unmodified and modified g-C3N4 was tested in the photodegradation of indigo carmine dye at pH = 3.5 and 6.5 solutions under blue LEDs light. The photostability of the samples was tested after 4 cycles of reaction. The properties (surface area (SA); water contact angle (WCA), and optical gap) influence the photocatalytic response, which was summarized in a single parameter defined as SA/(WCA*gap). The maximum value of this product match with results obtained for the most active photocatalyst (U-Hz1).

CAD-CAM denture teeth made on cast metal removable partial denture frameworks

Once the fit of the cast metal framework on a removable partial denture (RPD) has been verified, the manufacturer’s prefabricated denture teeth are typically secured on the cast metal framework to prepare for a wax evaluation. Although prefabricated denture teeth are available in different tooth forms and sizes, they require modification to fit an edentulous space. In arches with severe space discrepancy, it may be inefficient and time-consuming to make modifications to prefabricated denture teeth. The technique described uses digital technology to fabricate custom denture teeth on a cast metal framework and establish harmonious occlusion. An edentulous space with more than a single tooth replacement is designed as a splinted fixed partial denture with a connector. The designed teeth are milled in the double-cross-linked polymer to prepare for a wax evaluation, and once verified, the RPD is processed by using heat polymerization. Modifications are made to the milled denture teeth after wax elimination to reduce the likelihood of acrylic resin bond failure.

Effect of Low Nanodiamond Concentrations and Polymerization Techniques on Physical Properties and Antifungal Activities of Denture Base Resin.

Background: Denture base resin has some drawbacks. This study investigated the impact of nanodiamonds (ND) and autoclave polymerization on the surface characteristics, translucency, and Candida albicans adherence in polymethyl methacrylate (PMMA) denture base resin after thermocycling. Methods: Heat-polymerized PMMA discs (15 × 2 mm) with a total sample size n = 160 were studied. Specimens were categorized into two main groups (N = 80): conventional water-bath-polymerized PMMA (CP/PMMA) and autoclave-polymerized PMMA (AP/PMMA). Each group was subdivided according to the ND concentration into four groups (n = 20): unmodified PMMA as a control, and 0.1%, 0.25%, and 0.5% ND–PMMA. Scanning electron microscopy (SEM) was used to inspect the morphology of the ND and the ND–PMMA mixtures before heat polymerization. The specimens were exposed to thermal cycling (5000 cycles at 5 and 55 °C), then surface roughness was measured with a non-contact optical interferometric profilometer, contact angle with an automated goniometer, and translucency using a spectrophotometer. Colony-forming units (CFU) were used to determine the adherence of Candida albicans cells to the specimens. ANOVA and Tukey post hoc tests for pairwise comparison were utilized for the statistical analysis (α = 0.05). Results: Surface roughness was significantly reduced with ND addition to CP/PMMA (p ˂ 0.001), while the reduction was not statistically significant in AP/PMMA (p = 0.831). The addition of ND significantly reduced the contact angle, translucency, and Candida albicans count of CP/PMMA and AP/PMMA (p ˂ 0.001). The incorporation of ND in conjunction with autoclave polymerization of PMMA showed significant reduction in all tested properties (surface roughness, contact angle and Candida albicans adherence) except translucency (p = 0.726). Conclusions: ND addition to PMMA and autoclave polymerization improved the surface properties with respect to antifungal activities, while the translucency was adversely affected.

Antifungal effectiveness of soursop (Annonamuricata Linn) leaves extract againts Candida albicans on heat cured acrylic

Objective: The use of removable dentures can cause chronic inflammation, namely denture stomatitis, caused by Candida al-bicans; with a prevalence of 15-70%. Soursop (Annonamuricata Linn) leaf extract contains alkaloids, tanin, flavonoids, and sa-ponins that act as antifungals. This study is intended to evaluate whether soursop leaf extract solution can effectively reduce the number of C.albicans colonies in heat polymerized acrylic resins. Method: With true experimental pre-post test with control group design, 25 resin plates were divided into 5 groups, 3 groups were tested with soursop leaf extract (10%, 15% and 25%), while Fittydent® and aquadest were the control groups. Samples are contaminated with C.albicans suspension and incubated; calculated before immersion 8 hours, then put in Saboroud's brouth and recalculated. Result: Wilcoxon test showed significant differences in all groups, except the aquadest group. The Mann-Whitney test compared a decrease in the number of C.albicans colonies between groups, showed significant differences between treatment groups, except between the extract group of 25% and fittydent control®. Conclusion: Soursop leaf extract solution lowers the number of C.albicans colonies in heat polymeri-zation acrylic with the most effective concentration of 25%.

Disinfection Effect of 10% Ricinus Communis Oil on Candida Albicans Counts of Heat Polymerized Acrylic Resin

Dentures is used to replace tooth loss. The most used denture base material is acrylic resin. The biological properties of acrylic resins give microorganisms the ability to colonize. Certain type of microorganism often found at the dentures base is Candida albicans. Denture’s disinfection is usually used to reduce Candida albicans. One of natural source that now is being widely researched is Ricinus communis oil. The purpose of this study was to analyze disinfection effect of Ricinus communis oil 10% on Candida albicans counts on heat polymerized acrylic resin. This research is an experimental laboratory study with a post-test only design. Samples was heat polymerization acrylic resin plates measuring 10 x 10 x 1 mm were made in the Department of Prosthodontic Faculty of Dentistry, Universitas Sumatera Utara with 10 plates for each for 10% Ricinus communis oil group and 0.2% chlorhexidine gluconate group (control). The Candida albicans colonies count was carried out in the Microbiology Laboratory, Faculty of Mathematics and Natural Sciences, Universitas Sumatera Utara using colony counter. The data obtained was statistically count with the Kruskal-Wallis Test. The result showed the decrease in Candida albicans count with the highest value in the 10% Ricinus communis oil group is 9 x 100 CFU/ml and the highest value in the 0.2% chlorhexidine gluconate group is 0 x 100 CFU/ml. The Kruskal-Wallis test showed significant results with p value of 0.0001 (p &lt;0.05) indicating there was a disinfection effect of 10% Ricinus communis oil and 0.2% chlorhexidine gluconate on Candida albicans count of heat polymerized acrylic resin. The study concluded that 10% Ricinus communis oil effective at decreasing Candida albicans count.

Catalase-like quantum dots of l-lysine polymerization as free radical scavengers for hypoxic brain injury

Hypoxemia as one of the most common symptoms of traumatic brain injury (TBI) can significantly exacerbate the development of secondary damage, which further contributes to generating large numbers of neurotoxic factors such as reactive oxygen and nitrogen species (RONS), pro-inflammatory cytokine and chemokine. Here, we developed a kind of quantum dots as catalase-mimic and multiple free radical scavengers by means of the microwave heating polymerization of l-lysine. Hydrogen peroxide as overproduced radicals can be decomposed to supply oxygen, contributing to improving the hypoxic condition in brain. Simultaneously, other traditional RONS such as O2−, OH, NO and ONOO− can be eliminated by the quantum dots. The total ROS level is back to normal after the quantum dots treatment, promoting the H2O2/LPS-stimulated cell survival in vitro. Oxidative stress induced by hypoxic brain injury is restored by the quantum dots intravenous injection, leading to the protection of neural cells in vivo. Additionally, the quantum dots can improve the spatial learning and memory of TBI mice by water maze test. This work provides a new perspective for the therapy of hypoxic brain injury.

Estimation of IZOD impact strength between different concentrations of chitosan-reinforced denture base resins.

Poly-methyl methacrylate (PMMA) is an universally acceptable denture base material. Efforts are made to increase the applications with the addition of new constituents. Chitosan has established antifungal properties. The mechanical properties of Chitosan-denture base composite is less evaluated in the literature. This study estimates the differences in impact strength of material for different concentrations of chitosan-reinforced denture base resins. The study estimated the differences in IZOD impact strength of denture base resin reinforced with 0%, 5%, 10% and 15% of chitosan by weight. The acrylic samples were fabricated in according to ISO 180 regulations. The study had four test groups (n = 10). ACh0 was the control group with no reinforcements. ACh5, ACh10 and ACh15 had chitosan reinforcement of 5%, 10% and 15% by weight. The samples were processed by conventional heat polymerization cycle and tested in IZOD impact testing machine. The data were recorded and statistically analyzed with Kruskal-Wallis test. The mean impact strength was high in ACh5 (4.25 ± 1.05 kJ/m2) compared to ACh0 (2.88 ± 0.60 kJ/m2), ACh10 (3.63 ± 0.40 kJ/m2), ACh15 (3.38±0.60 KJ/m2). Statistically significant differences between the test groups was determined by Kruskal-Wallis and post hoc Bonferroni test (Chi-square = 12.843, P = .005, df = 3). The impact strength of denture base resin increased with 5% chitosan compared with other percentage of chitosan. No statistical significant relationship was observed between the groups.