جستجوی مقالات مرتبط با کلیدواژه « composite » در نشریات گروه « پزشکی »

Composite resins undergo changes in properties due to various oral irritations over time. This study analyzed the effect of semi-nutritious liquids on the shear bond strength of repaired composite with universal bonding

This laboratory experiment used 80 samples of rectangular cubes made of Z250 composite. The samples were subjected to Thermocycling in an incubator and divided into four experi-mental groups, one control group, and stored in different solutions for seven days. After the aging process, the samples were roughened, bonding was applied, and a composite cylinder was placed on the previous composite. The bond strength was then calculated with an Instron device, and the data were analyzed using one-way ANOVA and Bonferroni's post hoc test (α=0.05).

Maximum average of bond strength in semi-nutrient liquids was recorded in descending order 25.53MPa for saliva , distilled water (20.24MPa), ethanol (18.04 MPa), citric acid (16.24 MPa), and Hep-tane (9.83 MPa), respectively.

Artificial saliva yielded the highest average bond strength, while distilled water, ethanol, citric acid, and heptane resulted in decreasing bond strength.

In recent years, bleaching materials have been used in many clinics, which may have different effects on natural teeth and composite restorations (omnichroma). The aim of this study is to determine the spectrophotometric effect of external bleaching on natural tooth structure and composite restoration.

In this study, cavities were first created on 26 extracted teeth, and then, omnichroma composite restorations were completed for all these teeth. The color of each tooth sample was evaluated with a colorimeter device. Measurements were obtained before the application of the bleaching agent for initial lightness (L0), after the bleaching agent's first application (L1), and after the second application of the bleaching agent (L2). Total color change difference (ΔE) values between the restorations and natural tooth during first (ΔE1) and second (ΔE2) treatment intervals were compared.

This study found that, as lightness values between natural tooth and composite were compared, there are changes of lightness value; L1 (p=0.000) and L2 (p=0.006) showed that there is a significant difference in lightness value (L) between natural tooth and composite restoration during the first and second treatments. However, the comparisons of total color change (ΔE) found no substantial differences between the composite restoration and natural tooth structure during the first and second treatment intervals ΔE1 (p=0.479) and ΔE2 (p=0.821).

According to the results of this study, the value of ΔE decreased significantly from L0 to L2 bleaching treatments. As the tooth becomes brighter, it is clear that there is less of a color difference between the omnichroma restoration and the tooth structure.

3D printing is a novel approach in the pharmaceutical field, but its usage has not been fully established. This method can promote drug therapy and overcome some traditional treatment challenges in different ways that are discussed in this paper. “One-size-fits-all”, Large-scale production, and less patient and physician acceptability are some limitations that we will encounter in traditional therapy. Three-dimensional printing of pharmaceutical products is a versatile technology that needs specific attention. Droplet-based, extrusion-based, and laser-assisted 3D printers are three main techniques that can be used in this field. The limitations and advantages of this method have been discussed, highlighting potential innovative pathways towards the possibility of drug carriers’ usage in ink formulas. The administration pathway of drug-loaded composites is another critical issue in drug treatment strategies that have been discussed here. Oral drug delivery as a convenient method of systemic drug administration with significant patient preference is introduced as the most prevalent pathway that has been studied about 3D printed medicines. Finally, essential ethics and future directions of 3D printing in the pharmaceutical and healthcare industries are outlined.

Statement of the Problem:

 Tooth-colored composites are used to repair caries lesions and other dental defects, particularly in anterior regions in children. Although a wide range of composites is using, little attention has been paid to the important indicators such as biological profiles or products released from these materials.

The current study aimed to compare the histocompatibility and cytotoxicity of light-curing resin used to repair children's teeth with different brands (3M, DenFil, and Opallis) in curing times of 20 and 40 seconds in human oral fibroblast cells (HGF1).

 In this in vitro study, Three types of flow composites (3M, Opallis, and DenFil), all at A2 shade, were used. The composites were at 4×2mm with separate exposure times of 20 and 40 seconds. MTT test was used to determine the cytotoxicity of composites on oral fibroblast cells. This test is based on the conversion of tetrazolium bromide to a purple compound known as formazan that its color intensity can be evaluated using the ELISA. The higher intensity of the color reveals the higher survival rate of the mitochondria, which indicates less toxicity. One-way variance analysis and unpaired t-test were used to compare the cytotoxicity of each brand in two conditions of 20 and 40 seconds of curing. Statistical significance was considered when p< 0.05.

3M and Opallis composites were significantly reduced vitality of cells compared to control group in both 20s and 40s curing status. While DenFil brand did not show marked cytotoxicity. In each brand, there are no significant deference between 20s and 40s curing times.

Histocompatibility depends on the type of composite resin. In the current study, DenFil brand showed the highest histocompatibility, followed by 3M and Opallis.

Effects of edible coatings, including sodium alginate (Alg), pullulan (Pul) and carboxymethyl cellulose (CMC) with bitter orange peel extract (BOE), on the chemical, microbial and texture qualities of chicken fillets during storage in refrigerator was investigated.

Samples treated with biopolymer coatings with BOE included significantly lower free fatty acids, peroxide value, total volatile basic nitrogen content and microbial count during cold storage, compared to fillets treated with pure BOE, biopolymer composites (no BOE) and controls.

Effectiveness of the coatings on bacterial population was as follows Alg/Pul/BOE > Pul/CMC/BOE > Alg/CMC/BOE > BOE > Alg/Pul > Alg/CMC > Pul/CMC > control. Coating fillet samples with pure BEO showed greater inhibitory activities against microbial spoilage, compared with composite coatings with no extracts.

Treatment efficiency as of antimicrobial agents and maintenance of physicochemical characteristics were as follows Alg/Pul/BOE > Pul/CMC/BOE > Alg/CMC/BOE. Based on the current findings, these composite coatings can be promising options to improve the quality of fresh foods during shelf-life.

In light of severe and growing shortages of clean water and the rising environmental pollution in many countries, seawater desalination has been an effective method to produce freshwater. Cationic membranes have enabled environmental scientists to effectively remove toxic heavy metals from wastewater and to regenerate freshwater.

We used a novel method, involving electro- and physico-chemical membranes to successfully remove toxic heavy metal ions (copper & chromium) from wastewater samples. Specifically, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, surface wettability, flux, selectivity and electrical resistance measurements were applied to conduct this study.

The obtained results illustrated relatively uniform foaming of the modified membranes. Also, electron microscopic images indicated almost even distribution of the particles. The dada indicated that applying polydopamine layer and incorporating nanofibers in monomer solution caused surface hydrophilic enhancement. Also, increased carbon nanofibers loading ratio to 0.07% raised the ionic flux. The data also showed a higher capacity in the modified membranes for the removal of copper and chromium ions from the wastewater samples. Although the surface modified membranes displayed a higher flux and lower permselectivity to some extents, utilizing nanoparticles led to a steady trend of ion elimination. Generally, carbon nanofibers incorporation to the membrane surface modified samples up to 0.1% weight, resulting in nearly a constant areal electrical resistance.

The novel method developed by this study is an excellent candidate with high potential for the removal of toxic heavy metal ions from wastewater samples.

Statement of the Problem:

 Sealants are placed to prevent carious lesion initiation and to arrest caries progression by providing a physical barrier that inhibits microorganisms and food particles from collecting in pit and fissures .The two most common materials used for sealing pits and fissures are resins and glass-ionomers. Ionoseal is a light curing GI composite cement.The aim of this study was to compare the microtensile bond strength and microleakage of Ionoseal with different surface pretreatment.

This in vitro ,an experimental study was conducted on 95 sound human premolar in 5 groups(in each group 5 teeth for microtensile test and 14 teeth for microleakage test).A :35% phosphoric acid + total etch adhesive + Ionoseal ,B :universal adhesive + Ionoseal ,C: 35% phosphoric acid + Ionoseal,D: Ionoseal, E: 35% phosphoric acid + Embrace fissure sealant. On the prepared buccal enamel of each tooth, a 5 mm block of the sealing material was created and underwent thermocycling .By serially cutting, specimens about1×1mm in cross section were obtained and loaded in tensile (0.5 mm/min) until failure occurred .For microleakage test,sealing material was placed into the prepared occlusal fissures and teeth were thermocycled and then immersed in methylene blue 5% .An incision was made buccolingually. The dye penetration rate was measured based on Williams and winter criteria under stereomicroscope.

Mean microtensile bond strength was significantly different between groups (P

Hydroxyapatite (HAP) is a natural calcium apatite mineral. Hydroxyapatite has many applications in the field of biomedicine and drug delivery systems. Titanium dioxide (TiO2) is becoming increasingly important because of its potential use in new medical treatments. In this study, titania-hydroxyapatite composite nanoparticles were evaluated as a potential drug carrier for ibuprofen.

Titania-hydroxyapatite composite nanoparticles (titania-HAP) with two different titania weight ratios (30 and 70 wt%) were prepared and loaded with ibuprofen (IBU) as a pain reliever drug. The composites were studied as potential carriers of ibuprofen by X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) analyzes, energy dispersive X-ray spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA). Cytotoxicity of nanocomposites was investigated in vitro on osteosarcoma cell line by MTT assay. 

The functional groups were investigated by FTIR. Size and morphology of samples were evaluated by FESEM and TEM. Chemical composition and phase formation were confirmed by EDX and XRD patterns. Based on the results of MTT assay, no significant effect was observed on MG-63 cell lines. TGA was used to determine the amount of ibuprofen loaded on the composites.

Ibuprofen release was studied in neutral and acidic simulated media by ultraviolet–visible (UV-visible) spectroscopy and the results showed better sustained release of the drug in acidic medium. Titania-hydroxyapatite composite nanoparticle can have a good potential for medicinal applications.

In recent years, the dye industry has been rapidly developed. Dyes are one in all the foremost dangerous groups of chemical compounds found in industrial effluents, which are of considerable importance for reasons like reduced light permeability and therefore the subsequent disruption of the method of photosynthesis in water sources. This study was performed to remove dye using Fe-Co-V /Zeolite from synthetic wastewater. 

After chemical synthesis of the nanocomposite, its structure by spectroscopic techniques was studied. Experiments were performed Under different pH conditions (3-11), contact time (5-50 minutes), absorbent dose (0.5-0.6 g), stirring speed (240-60 rpm), and different concentrations.

The results showed that the optimal and final conditions affecting the removal of methyl orange dye in the most suitable conditions for 200 mL of solution with a concentration of 20 mg/L at pH equal to 3, contact time 20 Minute, adsorbent weight 0.2 g, jar speed 180 rpm and temperature 25 °C, which finally with the application of optimal data, at a concentration of 2.5 mg/L, the best efficiency was obtained. Examination of isotherm diagrams and isotherm coefficients showed that the adsorption process follows the Freundlich equation.

According to the obtained results and physical and chemical properties of the synthesized nanocomposite, it can be used to remove pollutants from the environment such as wastewater and gaseous pollutants from the air.

 The recovery of rare-earth elements (REEs) like toxic lanthanides from contaminated waters is vital because of their irreversible effects on humans and the environment.

 In the present research, a chitosan-imprinted nano zero-valent iron (CS@nZVI) nanocomposite was fabricated and utilized to the successful separation of Lanthanum as a model lanthanides.

 The morphological and structural properties of the composites were studied through BET, FTIR, SEM, TEM, and XRD techniques. The adsorption process was modeled and optimized by methodology of response surface (RSM). Then, its four important models were validated by data fitting. Afterward, they were affirmed using ANOVA test.

 According to the outputs of the models, the reduced model was obtained as an appropriate model. Based on RSM plots, the adsorption rate at preliminary pH is low and gets better with increasing the pH value. At lower pH, there is a high concentration of H+ ion with smaller ionic radii and higher adsorption possibility, which makes it difficult to adsorb lanthanum ions by creating a competition between the excess of protons in the solution and cationic metal ions. This competitive adsorption and saturation of adsorptive sites on the surface of CS@nZVI sorbent with hydrogen ions together with repulsion forces are responsible for the La (III) less sorption. The optimum CS@nZVI removal efficiency of La (III) was 88% under the following conditions: pH = 8, 1.2 g/L CS@nZVI dosage, 5 mg/L initial La (III) concentration, and 180 min shaking time. Based on uptake kinetic models, the pseudo-second-order model is optimum in describing the rate equation of the adsorption process.

 Successfully regeneration of CS@nZVI along with its good performance for Lanthanum separation provide a promising and feasible method in order to contaminated streams purification.

 Sufficient bond strength of composite restoration leads to its durability and survival; therefore, preparation of dentin surface for higher bond strength is essential.

Our aim is to assess the deproteinizing effect of 3% bromelain enzyme and compare it to 4% titanium tetrafluoride (TiF4) and 5% sodium hypochlorite (NaOCl) regarding the shear bond strength (SBS) of composite resin to dentin.

In this experimental study, 40 intact extracted human maxillary premolars were selected, and the occlusal surfaces of the teeth were sectioned at a depth of 2 mm from dentinoenamel junction. The teeth were divided into 4 groups (n=10). In Group 1, the teeth were etched with 37% phosphoric acid gel. In Group 2, the teeth were etched and deproteinized with 5% NaOCl. In Group 3, the teeth were etched and deproteinized with 4% TiF4. In Group 4, the teeth were etched and deproteinized with 3% bromelain enzyme. In each specimen, composites with 3 mm diameter and 2 mm height were prepared and cured. The test specimens were then stored in distilled water at room temperature for 7 days before conducting the SBS test (MPa). By universal testing machine at a crosshead speed of 1 mm/min, the results were analyzed using one-way ANOVA and Tukey test.

One-way ANOVA test demonstrated that pretreatment of dentin with a bromelain enzyme, TiF4 solution, or NaOCl was not statistically different regarding SBS to dentin (p= 0.790).

3% bromelain enzyme can be as effective as TiF4 and NaOCl and phosphoric acid 37% in terms of the SBS of composite resin to dentin.