Acrylic Powder Research Articles

In Vitro Evaluation of the Inhibitory Activity of Thymoquinone in Combatting Candida albicans in Denture Stomatitis Prevention.

Candida albicans adhesion and proliferation on denture bases may lead to denture stomatitis, which is a common and recurrent problem in denture wearers. The goal of this study was to assess the inhibitory effect of thymoquinone incorporated in the polymethyl methacrylate denture base material against Candida albicans. Eighty acrylic resin specimens were fabricated and divided into eight groups (n = 10) according to thymoquinone concentrations of 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, and 5% of acrylic powder. Two methods were used to evaluate the effect of thymoquinone on Candida albicans: the slide count and the serial dilution test. A multivariate analysis of variance (MANOVA) and the post-hoc Tukey’s Honestly Significant Difference (HSD) test were performed to compare the difference of means between the observations taken at various intervals with baseline. The p value was statistically significant at ≤0.05. According to the slide count and the serial dilution test, the mean number of adhered Candida albicans in the control group was 5436.9 ± 266 and 4691.4 ± 176.8; however, this number dramatically decreased to 0 ± 0 and 32.4 ± 1.7 in group 8 (concentration 5%). These results suggest that the incorporation of thymoquinone into the acrylic resin denture base material might be effective in preventing Candida albicans adhesion.

Tensile strength and impact strength of color modified acrylic resin reinforced with titanium dioxide nanoparticles.

BackgroundPoor mechanical properties are among the main limitations of acrylic resins. Addition of titanium dioxide (TiO2) nanoparticles to acrylic resin has been shown to improve its mechanical properties with an adverse effect on its color. Thus, this study sought to assess the tensile and impact strength of a color modified heat cure acrylic resin reinforced with TiO2 nanoparticles.Material and MethodsIn this in vitroexperimental study, 1wt% TiO2 nanoparticles were added to SR Triplex Hot heat-cure acrylic resin powder and mixed. Pigments and color fibers were also added and 18 samples were fabricated of this paste for tensile and impact strength testing (n=9) according to ISO5271. Eighteen control samples were also fabricated from the acrylic powder without any modification. Independent t-test was used for data analysis (P< 0.05).ResultsThe mean tensile strength of the reinforced group was found to be significantly higher (difference of 11 MPa) than that of the control group (P=0.001). The mean impact strength of the reinforced group was 7 MPa higher than that of the control group and this difference was statistically significant as well (P=0.001).ConclusionsThe color modified acrylic resin reinforced with 1wt% TiO2 showed significantly higher tensile and impact strength compared to the conventional acrylic resin. Thus, TiO2 nanoparticles may be incorporated into color-modified acrylic resin powder to enhance its tensile and impact strength, given that they have no adverse effect on other properties. Key words:Tensile strength, acrylic resins, titanium dioxide, impact strength.

Influence of incorporation of ZrO2 nanoparticles on the repair strength of polymethyl methacrylate denture bases.

BackgroundRepeated fracture of the denture base is a common problem in prosthodontics, and it represents a nuisance and a time sink for the clinician. Therefore, the possibility of increasing repair strength using new reinforcement materials is of great interest to prosthodontists.Aim of the studyThis study aimed to evaluate the effects of incorporation of zirconia nanoparticles (nano-ZrO2) on the flexural strength and impact strength of repaired polymethyl methacrylate (PMMA) denture bases.Materials and methodsOne hundred eighty specimens of heat-polymerized acrylic resin were fabricated (90 for each test) and divided into three main groups: one control group (intact specimens) and two groups divided according to surface design (45° bevels and butt joints), in which specimens were prepared in pairs to create 2.5 mm gaps. Nano-ZrO2 was added to repair resin in 2.5 wt%, 5 wt%, and 7.5 wt% concentrations of acrylic powder. A three-point bending test was used to measure flexural strength, and a Charpy-type test was used to measure impact strength. Scanning electron microscopy was used to analyze the fracture surfaces and nano-ZrO2 distribution. The results were analyzed with a paired sample t-test and an unpaired t-test, with a P-value of ≤0.05 being significant.ResultsIncorporation of nano-ZrO2 into the repair resin significantly increased flexural strength (P<0.05). The highest value was found in the bevel group reinforced with 7.5% nano-ZrO2, whereas the lowest value was found in the butt group reinforced with 2.5% nano-ZrO2. The impact strength values of all repaired groups were significantly lower than those of the control group (P<0.05). Among repaired groups, the higher impact strength value was seen in the butt group reinforced with 2.5% nano-ZrO2. The bevel joint demonstrated mainly cohesive failure, whereas the butt joint demonstrated mainly adhesive failure.ConclusionIncorporation of nano-ZrO2 into the repair resin improved the flexural strength of repaired denture bases, whereas it decreased impact strength, especially with high nano-ZrO2 concentrations.

Comparative Study of Different Materials for Occlusal Matrix Technique in Posterior Teeth

Posterior composite restorations are difficult to contour and polish due to their occlusal anatomy and opposing occlusion. Our study describes a technique for duplicating occlusal surface anatomy, using different dental materials that are able to copy anatomic details. The aim of the study was to evaluate the efficiency of occlusal matrix technique, by comparing technical ease of different dental materials. The study was conducted on extracted teeth which had intact occlusal surfaces or initial carious lesions at this level. An impression of the occlusal surface was made prior to cavity preparation, with four different dental materials: a flow composite, a dual-cure resin cement, a temporary acrylic resin (powder and liquid) and a temporary crown and bridge two-component material in a Unidose®. When the last layer of composite has been placed, the occlusal matrix was forced into the uncured composite to replicate the original occlusal surface, instead of performing manual curing and shaping as in the standard approach. Time needed for complete finishing the case, the hardness of each occlusal matrix and the final morphology obtained were evaluated. The main benefits of the occlusal matrix technique are the technical ease of use due to its simplicity and its high accuracy in reconstructing occlusal morphology. Although the shortest time needed for occlusal matrix preparation was for the dual-cure resin cement, the best oclusssal matrix was obtained with the temporary acrylic resin (powder and liquid).

Antimicrobial properties of poly (methyl methacrylate) acrylic resins incorporated with silicon dioxide and titanium dioxide nanoparticles on cariogenic bacteria

Aim:To assess the effects of adding nano-titanium dioxide (nano-TiO2) and nano-silicon dioxide (nano-SiO2) and their mixture to poly (methyl methacrylate) (PMMA) to induce antimicrobial activity in acrylic resins.Materials and Methods:Acrylic specimens in size of 20 mm × 20 mm × 1 mm of 0.5% and 1% of nano-TiO2 (21 nm) and nano-SiO2 (20 nm) and their mixture (TiO2/SiO2 nanoparticles) (1:1 w/w) were prepared from the mixture of acrylic liquid containing nanoparticles and acrylic powder. To obtain 0.5% and 1% concentration, 0.02 g and 0.04 g of the nanoparticles was added to each milliliter of the acrylic monomer, respectively. Antimicrobial properties of six specimens of these preparations, as prepared, were assessed against planktonic Lactobacillus acidophilus and Streptococcus mutans at 0, 15, 30, 45, 60, 75, and 90 min follow-up by broth dilution assay. The specimens of each group were divided into three subgroups: Dark, daylight, or ultraviolet A (UVA). The percent of bacterial reduction is found out from the counts taken at each time point.Statistical Analysis:Data were analyzed using one-way analysis of variance and Tukey's post hoc analysis.Results:Exposure to PMMA containing the nanoparticles reduced the bacterial count by 3.2–99%, depending on the nanoparticles, bacterial types, and light conditions. Planktonic cultures of S. mutans and L. acidophilus exposed to PMMA containing 1% of TiO2/SiO2 nanoparticles showed a significant decrease (P < 0.001) (98% and 99%, respectively) in a time-dependent manner under UVA. The S. mutans and L. acidophilus counts did not significantly decrease in PMMA containing 0.5% nano-TiO2 and PMMA containing 0.5% nano-SiO2 in the dark. No statistically significant reduction (P > 0.05) was observed in the counts of S. mutans and L. acidophilus in PMMA without the nanoparticles exposed to UVA.Conclusions:PMMA resins incorporated with TiO2/SiO2 nanoparticles showed strong antimicrobial activity against the cariogenic bacteria.

OS0411 硬化過程の紫外線硬化樹脂に生じる流動

The flow and temperature of ultraviolet (UV) curable resin during curing were measured, and it was investigated whether the flow of the resin is related to the heat generated by the chemical reaction in the resin. The specimen consisted of a mold and UV curing resin in liquid form with acrylic powder. The mold consisted of glass, KBr and acrylic plates. The specimen was irradiated from below with UV rays. The flow and temperature were simultaneously measured using particle image velocimetry (PIV) and thermographic techniques, respectively. Results indicated that the flow of the resin in the initial stage of curing was due to the shrinkage of the resin, and that after the initial stage was mainly due to thermal convection in the resin generated by the chemical reaction.

Evaluation of polymethyl methacrylate resin mechanical properties with incorporated halloysite nanotubes.

PURPOSEThis study inspects the effect of incorporating halloysite nanotubes (HNTs) into polymethyl methacrylate (PMMA) resin on its flexural strength, hardness, and Young's modulus.MATERIALS AND METHODSFour groups of acrylic resin powder were prepared. One group without HNTs was used as a control group and the other three groups contained 0.3, 0.6 and 0.9 wt% HNTs. For each one, flexural strength, Young's modulus and hardness values were measured. One-way ANOVA and Tukey's test were used for comparison (P<.05).RESULTS At lower concentration (0.3 wt%) of HNT, there was a significant increase of hardness values but no significant increase in both flexural strength and Young's modulus values of PMMA resin. In contrast, at higher concentration (0.6 and 0.9 wt%), there was a significant decrease in hardness values but no significant decrease in flexural strength and Young's modulus values compared to those of the control group.CONCLUSIONAddition of lower concentration of halloysite nanotubes to denture base materials could improve some of their mechanical properties. Improving the mechanical properties of acrylic resin base material could increase the patient satisfaction.

MECHANICAL PROPERTIES AND RELIABILITY OF GLASS-ALUMINIUM COMPOSITE AS INSERT MOLD

Plastic injection mold made of tool steel is generally utilized for large lots production. Running for small lots of product is a new trend of demand, so that the mold would be relatively expensive and not competitive. The aim of the present work is to find an alternative material and process for low cost injection mold that suitable for small lots. For these reasons, aluminum-glassacrylic particulate composite would be proposed as a material for manufacturing of low cost plastic injection mold. In this work, an insert mold as part of the injection molding was selected for the case study. Composite was examined to know its characteristics. The part with size of (80mm x 10mm x 10mm) and (30mm x30mm x30mm) made of particulate composite material was selected as specimen. Material of the specimen was aluminum powders (<297 μm), glass powders (<74 μm) and acrylic powders (<74 μm); the volume ratio is 1:1:1. Acrylic was used for binder when composite made by layer manufacturing method, using Selective Heater Melting (SHM) machine. The specimen was prepared into three steps: manufacturing of composite (green specimen) by SHM machine, heating green specimen to burn up the acrylic, and resin impregnation. There were 3 types of specimens: green specimen before heating at 700°C, green specimen after heating at 700°C, and green specimen after heating at 700°C that continued by resin impregnation. Tests was performed to investigate its bending strength, surface hardness, surface roughness, and dimensional error. The other composite (specimen) was insert mold, made by layer manufacturing method, using SHM machine. Case study was carried out by testing an insert mold to know the reliability of insert mold. Bending strengths of green specimen, before and after heating at 700°C, were 2.07 and 8.23 MPa, respectively; and after resin impregnation was 17.15 MPa. Dimensional errors in the direction of X, Y, and Z-axis for green specimen of (30mm x 30mm x30mm) before heating at 700°C were 8.65, 2.7, and 3.8 mm, respectively; and after heating at 700°C were 7.90, 1.10 and 0.90 mm, respectively. Surface roughness of green specimen before and after heating at 700°C were 46.12 and 33.48 μm, respectively; and after resin impregnation was 12.17 μm. Surface hardness of specimen after resin impregnation was 14.199 BHN. The amount of plastic parts that could be produced by insert mold was 120 and 126 pieces. Although mechanical strength of this composite was lower than that of tool steel that used for common plastic injection mold, but this composite material was less expensive and suitable for small lots production.

In vitro biomechanical testing of different configurations of acrylic external skeletal fixator constructs.

To evaluate the in vitro biomechanical properties of four different configurations of acrylic external skeletal fixator constructs. Simulated bone constructs were prepared using two segments of 20 mm ultra-high-density polyethylene rods with a gap of 5 mm. The full pins (1.5 mm) were passed through the proximal and distal segments of ultra-high-density polyethylene rods, in the same plane, parallel to each other in configuration U, and were crossed in the M1, M2 and C configurations at a 90° angle to each other. Configuration U was a single bilateral uniplanar construct, M1 was a double orthogonal bilateral construct, M2 was a double orthogonal bilateral construct with proximal and distal connecting articulations, and C was a double orthogonal bilateral construct with proximal and distal circumferential articulations. Temporary scaffolds of different external skeletal fixator configurations were constructed using commercially available polyvinyl chloride pipes (20 mm) connected and secured to the fixation pins at a fixed distance from the rods. Acrylic powder (polymer) mixed with liquid (monomer) was poured into the pipes and allowed to solidify to form the side bars and rings. The external skeletal fixator constructs were then subjected to axial compression, cranio-caudal three-point bending and torsion (n = 4 each) using a universal testing machine. Mechanical parameters, namely stress, strain, modulus of elasticity, stiffness and bending moment of fixator constructs, were determined from load-displacement curves. Configuration U was the weakest and configuration C was the strongest under all the testing modes. Under compression, the M1, M2 and C configurations were similar. Under bending, a significant difference was observed among the uniplanar, multiplanar and circular configurations with no difference between M1 and M2. However, under torsion, all the external skeletal fixator configurations differed significantly. The freeform external skeletal fixator using acrylic as a replacement for a metallic bar may be useful to treat bone fractures and luxations in small animals, as it is mechanically strong, lightweight, economical, and pins can be passed from any direction depending upon the clinical situation.

Effect of silver nitrate incorporation into heat polymerized acrylic resin on some mechanical properties

Background: Polymers are very rarely used in their form. These modifications are carried out in order to improve the properties of polymers.Recently silver have been used successfully as antimicrobial (medical and dental) biomaterials that can prevent caries and infection of implants Purposes: The aim of the present in vitro study is to evaluate the effect of addition of silver nitrate to acrylic resin in different concentrationsthrough several tests part of these are: The effect of this additive on impact strength, transverse strength, and tensile strength of AgNO3 – loaded resin, and to assess any effect of addition of silver nitrate on coloration of acrylic resin. Materials and methods: Different concentrations of silver nitrate (9.375, 15, 30, 60, 120, 150, 300, 600 and 900 ppm) were prepared from stock solution of 1000 ppm silver nitrate. The specimens were prepared in accordance with the manufacturer's instructions and the tested silver nitrate solution was added to the acrylic resin powder and monomer in a fixed volume (0.2ml). Controls devoid of silver nitrate were included. Results: Fourier transform infra-red confirmed that there was no chemical bond between the Poly methyl methacrylate and silver nitrate. There was insignificant increasing (P=0.05) in impact strength observed when compared with control group. In transverse strength test, significant reduction was show (P<0.001). While for tensile strength there was insignificant reduction with 9.375(P=0.05NS) and 15(P=0.42NS) ppm silver nitrate. However, it was significant above 15 ppm (P<0.001). Darkening of silver nitrate -loaded resins were shown to be started with concentration of silver nitrateof 300 ppm and above. Conclusions: The additions of silver nitrate to acrylic resins yield good color stability and mechanical properties, depending on the concentration of silver nitrate.

Synthesis and powder generation of powder coatings using supercritical carbon dioxide

This paper reports an integral continuous process of polymerization and micronization of powder coatings using supercritical CO2 as solvent. Combining different process steps into one single process, using ultra short production chains, can be one future use of supercritical fluids. This contribution is therefore an example of how such integral processes can be designed and how the development of new products can look like using supercritical fluids. An acrylic resin consisting of glycidyl methacrylate, methyl methacrylate and styrene was chosen as polymer system for use of thermosetting material for acrylic powder coating application. The reaction was performed in a tubular reactor. A monomer conversion of more than 96% was achieved with short reaction times of about 30min at a temperature of 135°C and at a pressure of 30MPa in a homogeneous CO2 phase. The resulting polymer has a number average molecular weight of about 2500g/mol with a narrow polydispersity index of 1.6. In this process, the synthesis step in compressed carbon dioxide was followed by a high pressure micronization using the well-known PGSS process. Thus, small particles of about 25μm were obtained. Simultaneously, residual monomers were removed from the polymer product with the escaping CO2-gas, achieving a high purity grade. The process is designed as a straight forward process combining synthesis, micronization and purification of a polymer without depressurization between the unit operations and demonstrates the benefits which supercritical fluid technologies offer for product and process development.

Does Addition of Silver Nanoparticles to Denture Base Resin Increase Its Thermal Conductivity

Objective: Studies have demonstrates that physical properties of denture base affect patient satisfaction and acceptance. Thermal conductivity is among the most important properties of denture base influencing the sense of taste and gingival health. The conventionally used acrylic resin has a low coefficient of thermal conductivity. This study aimed to improve the thermal conductivity of acrylic resin by adding small concentrations of nanosilver.Methods: In this laboratory experimental study, 0.2wt% and 2wt% silver nanoparticles measuring 10-100 nm were mixed with the conventional denture base acrylic powder. Cylindrical samples were fabricated and thermal conductivity was measured. One-way ANOVA and Scheffe’s post-hoc test were used to compare the mean thermal conductivity of different groups. Data were analyzed using SPSS 15 and p<0.05 was considered statistically significant.Results: The thermal conductivity of resins reinforced with nanosilver was significantly higher than that of the conventional resin. By increasing the amount of nanoparticles in the acrylic powder, thermal conductivity further increased.Conclusion: Addition of small amounts of nanosilver to denture base acrylic resin increases its thermal conductivity.

Property modification of chloroprene rubber by addition of ultra-fine acrylic rubber powder

The role of ultra-fine pre-vulcanised acrylic rubber powder (ACMP) in properties of chloroprene rubber (CR) was studied. ACMP was incorporated into CR at various loadings and the properties of the ACMP filled CR were investigated. Owing to the high thermoplastic nature of the ACMP, better processability is obtained with increasing ACMP loading. Even though the presence of ACMP gives negative effect on cure rate and state of cure, both modulus and hardness of the vulcanisates increase continuously with increasing ACMP loading. The tensile strength is also improved with increasing ACMP loading up to 20 phr. Nevertheless, elasticity and abrasion resistance of the vulcanisates are impaired as the concentration of ACMP is increased. This is mainly attributed to the combination of dilution effect and reduced crosslink density. Since ACMP is fully saturated and highly polar, the incorporation of ACMP into CR gives rise to enhanced aging and oil resistance of the vulcanisates.

An Autoclave Effect on the Powder of Poly Methylmethacrylate

Background: Although most of the physical and mechanical properties of denture base resin polymerized by the conventional heat polymerization have been studied, the effect of autoclave processing on these properties has not been fully determined. The effect of autoclave on acrylic powder has not studied before. Materials and methods: Vertex was the heat – cured acrylic denture base material included in this study. A total of 90 specimens were prepared, the specimens were grouped into three control groups of Vertex acrylic resin which(group A) as curing by conventional water- bath technique (74oC for 90 minutes, then boil for 30 minutes, (group B) which curing by water- bath (100°C for 30 minutes), and (group C)which curing by autoclave (120 °C under 1.4 bar for 45 minutes). The other three groups of Vertex acrylic resin after treatment of powder by autoclave in 132 °C for 4 hours, and then grouped into (A1,B1 andC1) which curing as previously. To study the effect of treatment of powder of acrylic resin byautoclave and the effect of autoclave processing. Three tests were conducted surface roughness (profilometer tester), transverse strength (Instron universal testing machine), and surface hardness (Shore D). The results were analyzed to Descriptive Statistics and ANOVA test. Results: There were no significant differences in surface roughness in all studying groups. There was a highly significant difference in transverse strength test results between studying groups. There was a significant difference in surface hardness test results between studying groups. Conclusions: The treatment of powder of acrylic resin by autoclave had no significant differences in surface roughness, but had a highly significant Difference in transverse strength in all test results, and a significant difference in hardness surface test in group B1. The autoclave processing technique might also be a good alternative to the conventional water- bath processing technique.

Influence of Glass Fiber wt% and Silanization on Mechanical Flexural Strength of Reinforced Acrylics

The aim is to evaluate the flexural strength of acrylic resin bars depending on the addiction of glass fibers with or without previous 3-methacryloxypropyl-trimethoxysilane (silane) application. Short fibers (3 mm) were treated and added to an acrylic resin powder, being further mixed with acrylic liquid to create bars (25 × 2 × 2 mm) of 11 experimental groups (N = 10), according to the interaction of experimental factors: weight % of glass fibers: (0.5; 1; 3; 4; 6 and 7) and silane application (with silane (S) or without silane (N)). Flexural strength and scanning microscopy evaluation were performed (SEM). Data (MPa) were submitted to ANOVA and Tukey (α = 5%). A significant difference between groups was observed (p = 0.001): S7%(128.85 ± 35.76)a, S6% (119.31 ± 11.97)ab, S4% (116.98 ± 25.23)ab, N4% (107.85 ± 24.88)abc, S1% (96.29 ± 20.65)bc, S0.5% (89.29 ± 7.33)cd, S3% (89.0 ± 11.27)cd, N3% (86.79 ± 17.63)cd, N1% (85.43 ± 16.44)cd, Control (73.29 ± 25.0)de, N0.5% (59.58 ± 19.46)e. For N groups, it was not possible to include more than 4%wt fibers. SEM showed better fiber-resin interaction for S groups, and fractures around fibers on N groups. Previous silane application enables the addiction of greater quantity of glass fibers and better interaction with the acrylic resin resulting in higher flexural strength. Without silane, fibers seem to act as initial crack points due to poor interaction.

Influence of Zinc Content on Anti-Corrosion Performance of Zinc-Rich Coatings

The zinc-rich coating prevents steel from corrosion by sacrificing electrochemical cathode anode protection, but the zinc content is the most important parameter. In this paper, the zinc-rich coatings made with the amino resin, acrylic resin, complex solvents, auxiliary agents and high purity zinc powder. The coatings were applied onto steel substrate and then placed in neutral salt spray for 3000 h in order to study the anti-corrosion performance. The results showed that the anti-corrosion performance was promoted with the zinc content increasing. When the zinc content was higher than 86 wt. %, the anti-corrosion performance can be reached 3000 h. The anticorrosion mechanisms were studied by polarization curves and scanning electron microscope (SEM).

10401 紫外線硬化樹脂の硬化過程における流動と応力の同時測定(OS1-1【実験力学とその応用(1)】)

This study deals with the simultaneous measurement of the flow and stress of ultraviolet (UV) curable resin illuminated at UV ray. The flow is observed as particle trajectory patterns obtained using a particle tracking velocimetry technique, and stress as isochromatics, principal-stress directions and shear 45° obtained using a photoelastic technique, respectively; The specimens consist of glass plates, acrylic plates and UV curable resin in liquid form with acrylic powder. The specimens are illuminated with UV rays downwards from the upper side of the specimens, and the visual and photoelastic images of the resin in curing process are captured at a constant time interval using a digital and CCD cameras, respectively. Results indicated that the stresses in the resin during the curing, process depended on the degree of contact between the mold and the cured part of the resin and were almost independent on the flow of the uncured resin.

Effect of aerosol loading on breakthrough characteristics of activated charcoal cartridges

Charcoal cartridges are commonly employed to provide protection against a wide range of organic vapors at workplace owing to their excellent adsorption. In practical situations, not only organic vapors but also aerosol particles may exist in the workplace atmosphere. Focusing on aerosol particles, this study aimed to evaluate the effect of aerosol loading on both sorption capacity and breakthrough time of activated charcoal. Polydisperse corn oil aerosols with a mode of 0.2μm and monodisperse acrylic powder of 0.15 and 10μm were generated to load the test activated charcoal separately for conducting vapor sorption experiments. For liquid aerosol loading tests, the sorption capacities reduced by 14%, 38% and 46% and the 10% breakthrough times were shorten by 14%, 28% and 75% after loading 0.06, 0.14 and 0.25g of corn oil aerosols per gram charcoal, respectively. For charcoal loaded with solid aerosols, the sorption capacity remained unchanged whereas the 10% breakthrough times were reduced by 26%, 27% and 35% after loading 0.019, 0.027 and 0.029g of 0.15-μm acrylic powder per gram charcoal, and by 5%, 43% and 44% after loading 0.074, 0.13 and 0.18g of 10-μm acrylic aerosols per gram charcoal, respectively. It was concluded that the breakthrough characteristics were affected by aerosol loading and the sorption capacity of activated charcoal can only be reduced by the loading of liquid aerosols. For the use of gas respirators with activated charcoal cartridges, it should be noted that the service life of the charcoal cartridges could be shortened due to aerosol loading in a work environment, from the perspective of respiratory protection.

Assessment of zirconium oxide nano-fillers incorporation and silanation on impact, tensile strength and color alteration of heat polymerized acrylic resin

The mechanical strength and color stability of poly methylmethacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to assess impact, tensile strength and color stability of heat polymerized denture base after addition of salinated and non-salinated zirconium oxide (ZrO2) nano- fillers. Materials and methods: zirconium oxide nanofillers were incorporated into (PMMA) denture base by free radical bulk polymerization. The nano-particales were Silanated by coating with a layer of trimethoxysil ypropylmethacrylate (TMSPM) before dispersed and sonicated in monomer (MMA) in two percentages of 3% and 5% by weight. Then it was mixed with acrylic powder as general conventional method. One hundred and seventy five specimens were prepared for this study. fifty bar shapes specimens (80mm x 10mm X 4mm) for impact strength test, another fifty dumbbell shaped specimens (75mm × 12.75mm × 2.5mm ) were prepared for tensile strength test. On the other hand, seventy five disc shaped specimens (50mm diameter and 0.5mm thickness) were prepared for color stability test. They were divided into two groups according to the nanofillers used ; silanated and non-silanated ZrO2 nanofillers, for each group Three subgroups were prepared (one control and two(3% and 5%) for the silanated and non-silanated ZrO2 nano-fillers. Impact strength test was carried out with charpy type impact testing instrument. While tensile strength test were done by using Jain Qiao equipment system. . On the other hand, color stability was objectively assessed by using a spectrophotome ter device after 48 hours immersion in three different solutions (distilled water, cola and tea) and the amount of light absorption was calculated. Impact and tensile strength means (in MPa) and color stability means (in nm) were analyzed statistically by analysis of variance and the comparative T-test and least significance test (LSD). Result: Significant increase in impact strength occur in acrylic reinforced with 5% wt silanated (ZrO2) nanofillers , but non significant increase was observed at 5% wt non-silanated (ZrO2) nanofillers when compared with control group. On the other hand, there were non-significant improvements in the tensile strength for all groups of (ZrO 2) reinforcements. While for the color stability test data showed significant increase in the light absorptions for specimens reinforced with (ZrO2) nanofillers when compared with control group. on the other hand, there were no significant difference observed between specimens reinforced with non-silanated and silanated (ZrO2) nanofillers. Conclusion: the findings of this study showed that Silanaized ZrO2 nano-fillers is effective in improving impact strength while it was not effective in improving the tensile strength, the maximum increase in impact strength was observed in denture base nano composite containing 5% wt of silanated ZrO2 nano-fillers. On the other hand, significant color differences were detected between control group and specimens incorporated with zirconium oxide nano-fillers at

Anatomical and biomechanical study on the interosseous membrane of the cadaveric forearm

Objective To study the anatomical and biomechanical features of the interosseous membrane (IOM) of the cadaveric forearm. Methods Ten radius-IOM-ulna structures were harvested from fresh-frozen cadavers to measure the length, width and thickness of the tendinous portion of IOM. Then, the tendinous portion was isolated along with the ulnar and radial ends to which the tendon attached after measurement. The proximal portion of the radius and the distal portion of the ulna were embedded and fixed in the dental base acrylic resin powder. The embedded specimen was clamped and fixed by the MTS 858 test machine using a 10 000 N load cell for the entire tensile test. IOM was stretched at a speed of 50 mm/min until it was ruptured. The load-displacement curve was depicted with a computer and the maximum load and stiffness were recorded at the same time. Results The IOM of the forearm was composed of three portions: central tendinous tissue, membranous tissue and dorsal affiliated oblique cord. IOM was stretched at a neutral position, and flexed at pronation and supination positions. The tendinous portion of IOM was lacerated in 6 specimens when the point of the maximum load reached to 1021.50 N ± 250.13 N, the stiffness to 138.24 N/m±24.29 N/m, and the length of stretch to 9.77 mm±1.77 mm. Fracture occurred at the fixed end of the ulna before laceration of the tendinous portion in 4 specimens when the maximum load was 744.40 N ± 109.85 N, the stiffness was 151.17 N/m±30.68 N/m, and the length of the stretch was 6.51 mm±0.51 mm. Conclusions The IOM of the forearm is a structure having ligamentous characteristics between the radius and the ulna. It is very important for maintenance of the longitudinal stability of the forearm. The anatomical and biome-chanical data can be used as an objective criterion for evaluating the reconstructive method of IOM of the forearm.