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

The opacity of dental ceramics has important role in final appearance of all ceramic restorations. opacity of super high translucent zirconia is not clearly determined.The aim of this study was evaluating the opacity of two super high translucent zirconia (zolid fx and DD cubeX2) and lithium disilicate reinforced glass ceramic(IPS e.max CAD LT).

In this experimental study, 30 ceramic discs with 1 mm thickness and 10 mm diameter in two groups of super high translucent zirconia (zolid fx and DD cubex2) and one group of lithium disilicate reinforced glass ceramic (IPS e.max CAD LT) were fabricated(n=10). For determining the contrast ratio (CR), spectrophotometer was used to measure Y parameters of each sample in black and white backgrounds. One-way ANOVA and Tukey Post Hoc statistical tests were used to analyze the data. Level of significancy was 0.05.

The mean of CR in the three groups of IPS e.max CAD LT ، zolid fx and DD Cubex2 were 0.97 ± 0.002, 0.96 ± 0.004 and 0.96 ± 0.005 respectively. Significant differences were not found in the CR values of three groups (P = 0.2).

Regarding the limitation of this study, Opacity of three ceramic were similar.

Neonatal jaundice is an almost common problem among neonates that may cause complications such as kernicterus in severe cases. Since early diagnosis and proper treatment of neonatal jaundice is vital to prevent the related complications, it is necessary to check bilirubin before discharging the neonates. There are several evaluating and diagnostic methods to measure the level of bilirubin. Thus, this study aimed to compare the transcutaneous method versus measurement of serum bilirubin, using spectrophotometry for jaundice screening of full-term neonates before discharge from hospital.

This observational analytic study was conducted on six hundred neonates with birth weight more than 2000 grams and gestational age more than 35 weeks from September 2012 to March 2013 in Hafez hospital, Shiraz University of Medical Sciences. Parameters such as bilirubin level of neonates were measured and compared, using spectrophotometry and transcutaneous by Bili check with multi waves.

Six hundred neonates were enrolled in this study. The Pearson correlation test showed that there was a significant correlation between the two methods of the transcutaneous versus measurement of serum bilirubin, using spectrophotometry (r=0.63), (P>0.05). There was no significant difference between the mean of measured bilirubin, using each method in some demographic variables such as the different groups of gender (P=0.896), birth weight (P=0.419), and type of feeding in neonates (P=0.323), but it was significant in other demographic variables such as the different groups of gestational age and post-neonatal age (P<0.0001). Also, the results revealed that there was a significant correlation between two methods of the trans cutaneous versus measurement of serum bilirubin, using spectrophotometry based on demographic variables (P<0.0001).

In general, the bilirubin measurement using trans-cutaneous method may estimate bilirubin significantly less than the serum bilirubin measurement method, and this difference can be more obviously noticeable in infants with less gestational age and also less post-natal age.

Polyethylene terephthalate (PET) containers have many applications in the food industry. Although there are numerous advantages for PET it also has some disadvantages, one of which is the migration of materials from the container into the material inside. In this study, the effect of two factors of storage time and temperature on the migration rate was evaluated and modeled.

To design the experiments, the surface-response method (RSM) was used. First, the type of migratory material and the effective conditions on the migration of materials from polyethylene terephthalate containers to soft drinks were identified and investigated. The primary results showed that the two factors of time of contact of the beverage with the container and the temperature of the storage environment have a significant effect on the migration of polyethylene terephthalate into the beverage. After the initial studies, the amount of compounds transferred into the beverage was measured by the spectrophotometric method and these results were modeled using the level-response method.

The results showed that the association between material transfer rate, temperature, and time can be modeled as a two-dimensional power model. It can also be stated by the model that temperature and shelf life directly affect the transfer rate with ratios of 0.003 and 1.17, respectively. The rate of migration is directly related to the square of the storage time and the temperature of the storage environment. The shelf life of the beverage has a very high impact on the migration rate, and mathematically the migration rate can be considered as a function of the shelf life of the soft drink. In addition to the shelf life of the beverage storage temperature is also a very important factor in the migration rate and the combination of the two can increase the rate of migration exponentially.

Polyethylene terephthalate containers are not suitable for storing non-alcoholic carbonated beverages and have the potential to cause harm to consumer health.

Curcuma longa generally known as turmeric includes curcuminoids and sesquiterpenoids as components, which are known to have antioxidative, anticarcinogenic, and anti-inflammatory activities. Iron, magnetite, and hematite as a micronutrient play an important role in physiological and chemical processes. Chitosan is a natural polymer derived from chitin and is recognized as versatile biomaterials because of their high biocompatibility, nontoxicity, and biodegradability to harmless products. The purpose of this research was to design synthesis and loading of nanocurcumin on iron magnetic nanoparticles modified with chitosan which is used as a targeted drug.

This laboratory research was conducted in Aja University of Medical Sciences from May to November 2017. Loading of nanocurcumin on iron magnetic nanoparticles modified with chitosan was done in two steps. In the first step, after preparing chitosan and iron magnetic nanoparticles, chitosan is placed as a coating polymer on surface of iron magnetic nanoparticles. In the next step, the final reaction is done by adding nanocurcumin on iron magnetic nanoparticles modified with chitosan. This causes nanocurcumin to penetrate into the polymeric layer core shell nanoparticles.

Findings of transmission electron microscope and scanning electron microscope images show structure, morphology, physicochemical and the presence of nanocurcumin layers on chitosan in nanoparticles with diameter of 20 nm well. In Fourier transform infrared spectroscopy (FTIR), the Fe-O peak indicates magnetic nanoparticles and peak of the O-H in nanocurcumin layers on chitosan. Energy dispersive X-ray spectroscopy spectrum showing iron, carbon, oxygen and nitrogen peaks confirms the presence of these elements in the final composition and shows that chitosan and nanocurcumin groups are well dispersed on iron magnetic nanoparticles. The nanocurcumin loaded at 450 nm wavelength was evaluated by ultraviolet-visible spectrophotometry.

Results of Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope image, energy dispersive X-ray spectroscopy spectrum, transmission electron microscope image, vibrating sample magnetometer analysis indicated that nanocurcumin has been successfully loaded on iron magnetic nanoparticles modified with chitosan and can be used as a targeted drug.

Regarding the prevalence of monolithic zirconia and glazed ceramics IPS-e.max, and inadequate research on the color change of chlorhexidine and listerine mouthwashes on these two types,  this study was aimed to compare the effect of  these two mouthwashes on the stability of the
The mentioned materials.

This experimental study was carried out in vitro. 38 samples of monolithic zirconia and glazed ceramics IPS-e.max were prepared. The primary color was measured by spectrophotometry. The samples were randomly assigned to chlorhexidine, listerine and water mouthwashes. Developments for 7 days, every 2 minutes, in chlorhexidine 0/0 0.2%, Listerine Zero Then the secondary color was again measured by spectrophotometry and (4) ΔE  ab were evaluated by Kruskal Wallis test.

Both types of ceramics after the immersion in two types of mouthwash and distilled water were changed as control. ΔE values ​​of the two substance after being placed in chlorhexidine (Monolithic zirconium (ΔE = 0.16 ± 0.11) and glazed ceramics IPS-e.max
(ΔE = 0.39 ± 0.14) showed a significant difference compared to the initial colorimetry (P<0.001).Also, the amounts of ΔE, two  substances after placement in Listerine (monolithic zirconium (ΔE = 0.26 ± 0.17) and glazed ceramics IPS-e.max (ΔE = 0.48 ± 0.29) compared to colorimetric Primary difference was not significant (p <0.06). Kruskal Wallis test showed that this difference ΔE was significant between the four groups (p <0.02). 

The color consistency of both monolithic zirconium and Ips.emax ceramics seems to be clinically acceptable.

Today, in order to maintain or improve the appearance, composition, flavor and nutritional value for food, compounds called additive are added, that they lead to complications in the human body, which the colors are only one of these substances. The aim of this study was to determine the frequency of consuming colors in saffron foods in Fasa in 1397 by thin layer chromatography and spectrophotometry methods. This is a type of Experimental study that was conducted by a cross-sectional study in Fasa. A total of 64 samples of food were collected from restaurants and after color extraction with Hydrochloric acid and purification, the color analysis was performed using thin-layer chromatography and spectrophotometry. The Data were analyzed using Excel software. Out of 64 samples, 36 samples (56.2%) of natural color and 28 samples (43.8%) of artificial color were used. Of this amount, artificial color (57.1%) was non‐permitted artificial color (16 samples) and 42.9% of permitted artificial color (12 samples). Also, 75% of the natural colors used were saffron type. Considering the high level of artificial colors found in the samples of this study, preventive measures are essential because the high consumption of non-edible and edible color in foods and their adverse effects on health, raising the level of awareness of manufacturers and consumers about the complications, the amount of consumption or lack of use of these substances is necessary.

Background and Carbon monoxide poisoning is one of the common causes of mortality in developing countries, during the cold months of winter. At the moment, the final diagnosis is based on positive test of spectrophotometry. Considering that there are not laboratory facilities available all the time for carrying out this test. Therefore, we decided to review sensitivity and specificity of clinical findings in examination of corpse in comparison to spectrophotometry test in diagnosis of death due to carbon monoxide poisoning. All corpses with suspicious history of carbon monoxide poisoning, which were referred to the anatomy hall of the Tehran Laboratory Diagnostic Center from Aban to Esfand month of 1395, were examined. A blood sample from all of these bodies was taken to examination and conducted spectrophotometric testing in the toxic laboratory. Other information needed for this study was extracted from physician’s examination and autopsy of body and interview with relatives. Information of the cases were extracted and written in the prepared forms by an experienced physician. Data analysis was done using version 21 SPSS software. 107 bodies of males and 31 bodies of females were investigated. 112 cases died from carbon monoxide poisoning, and in 26 cases the cause of death were apart from carbon monoxide poisoning. In the study of clinical findings, in 110 cases bright red color of the hypostasis, in 92 cases bright red color of the conjunctiva, in 91 cases bright red color of the oral mucosa, in 99 cases bright red color of the nail bed and in 135 cases bright red blood were seen. In 110 cases spectrophotometric tests were positive and in 28 cases tests results were negative. On the other hand, 95 cases had positive clinical findings and 36 cases had negative clinical findings. Considering to the sensitivity of 94% and the specificity of 100% of the findings of clinical examinations in people who died due to carbon monoxide poisoning, as well as the positive predictive value of 100% and the efficiency of 94% of these findings, it can be concluded that if a body with the history of carbon monoxide poisoning refers to the anatomy hall and after examination of the corpse in sufficient light by the experienced physician, bright red color of the hypostasis, the nail bed, the blood and the oral mucosa and conjunctiva are observed, diagnosis of the carbon monoxide poisoning is suggested

Formaldehyde is considered as one of the most important air pollutants due to both its high toxicity, and the vast application in industries and medical centers. Many concerns have emerged, therefore, on the sensitivity and the accuracy of analysis methods for this compound. This study was carried out to evaluate the feasibility of the field application of headspace single-drop microextraction (HS-SDME) in preparation of formaldehyde-contained samples for gas chromatography analysis.
In this experimental and cross sectional study, air samples were collected from a rock wool manufacturing company using National Institute for Occupational Safety and Health (NIOSH) 3500 method. The samples were analyzed once using the standard method of NIOSH 3500 and the other time using HS-SDME and gas chromatography. Finally, the values of formaldehyde concentration calculated in the two methods were compared.
Findings: Paired t-test indicated that formaldehyde average concentration in HS-SDME (1.27 µg/ml) was significantly lower than that in NIOSH method (2.31 µg/ml) (P According to the results, HS-SDME method is possible to be efficiently applicable in the extraction of formaldehyde samples with low concentrations. However, it would not be accurately feasible in moderate and high concentrations.

The impact of external factors on color of ionomer glass as a restorative material is important due to its beauty. The aim of this study was to evaluate discoloration of conventional and resin-modified ionomer glass, after the application of fluoride varnish.
In this study, 16 samples of each ionomer glass Chemfil Superior (C) and (F) Fuji II LC were prepared. Then fluoride varnish Dura shield (Sultan, USA) was used on samples (Cf, Ff). The color of each sample was measured using a spectrophotometer (Gretage Macbeth, Color-eye7000A) and digital camera (Sony Cyber-shot DSC N1) before and after the application of fluoride varnish. Obtained data from camera was converted to color space Lab CIE by MATLAB software. Discoloration (ΔE) of each sample was calculated in spectrophotometer and digital camera and statistical analysis was performed.
FINDINGS: Using spectrophotometer ΔE in Cf and Ff groups was obtained 4.44 and 5.8, respectively, but with a digital camera was 2.37 and 4.21, respectively in the same group. The application of fluoride varnish in the evaluation of a spectrophotometer and a digital camera resulted in a statistical significant color change in samples (respectively p Based on the results of this study in evaluation by spectrophotometry, application of fluoride varnish (Dura shield) led to an apparent color change in both ionomer glass. According to the same results, digital camera for evaluation of color is relatively reliable.

Synthetic colorants are very important class of food additives. They are widely used all over the world in food and feed industries due to their low price, high effectiveness and excellent stability. In this research, a simple, rapid and sensitive method termed as “dispersive liquid-liquid microextraction” combined with spectrophotometry determination is proposed for determining the trace amounts of carmoisine in food samples.
Several factors influencing the extraction efficiency of carmoisine including the type and amount of extraction solvent and disperser solvent, pH, ionic strength, and amount of ion-pairing reagent were studied and optimized. The proposed method was validated by high performance liquid chromatography technique.
Under the optimal conditions, a good linear behavior over the investigated concentration ranges (10-2000 μg/L) with good correlation of determination, R2> 0.9993, was obtained. The relative standard deviation (RSD) based on six replicate determinations at 250 μg/L level of carmoisine was 6%. The extraction percent was 90%, and the limit of detection (LOD) of the proposed approach was 2.0 μg/L.
Dispersive liquid-liquid microextraction method coupled with spectrophotometric has good accuracy (spike recoveries greater than 95%) for determining the trace amounts of carmoisine (μg/L).

Increasing water resources pollution by heavy metals cause serious environmental and health concerns in the world. Selenium blood levels of >100 𝜇g/dl can result in selenosis. Atomic absorption spectroscopy is the most common method for selenium detection. This technique has several disadvantages such as high equipment and operational costs، time-consuming and the need for quality control of the test method. In this study، the HMS) Hexagonal mesoporous silica (activated by 4- (2-pyridylazo) -resorcinol (PAR) was used for spectrophotometric determination of selenium. The qualitative detection was done by colour change of sediment from orange to pink in water samples and the quantitative detection by a spectrophotometer. Various parameters such as pH، the initial concentration of the selenium، contact time، and the indicator doses were also examined. The results of this study showed that the qualitative and quantitative detection of selenium are better done with increasing the contact time. The best condition for selenium detection was observed at pH =10. Increasing the indicator doses had no significant effect on the identification process. Increasing initial concentration of selenium increased the pink colour formation and consequently enhanced accuracy of qualitative and quantitative detection. This study is a basic and applied research. The HMS sensor activated by 4- (2-pyridylazo) -resorcinol (PAR) can be used as an inexpensive and rapid indicator for quantitative (spectrophotometry) and qualitative (colour change) detection of selenium in water and wastewater in research and administrative unites.

Tooth colored restorations are the commonly used current approach for aesthetic problems associated with brown spots. Considering the importance of conservative dentistry, the aim of this in vitro study was to evaluate the efficacy of color correction using casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and resin infiltration after using 20% carbamide peroxide for brown spots in esthetic areas. In this experimental study, 70 human teeth samples with brown spots were collected. In the first step, 20% carbamide peroxide was applied and then samples were divided into two groups to be treated with CPP-ACP or resin infiltration. Color parameters of the samples were evaluated at baseline, after bleaching, after using infiltration resin and CPP-ACP. Any color shift was measured using spectrophotometer. The results were analyzed by SPSS version 20. For statistical analysis, paired t test, independent t-test and repeated measures ANOVA were used. P value<0.05 was considered significant. After using 20% carbamide peroxide, L* and b* increased and a* decreased significantly (p<0.001). By using CPP-ACP, decreases in a* and b* were not significant (p>0.05) but L* increased significantly (p<0.001). Application of infiltration resin caused a significant decrease in a* (p<0.001); however, the decrease in L* and the increase in b* were not statistically significant (p>0.05). Comparison of the two groups showed that the degree of color shift (ΔE) in brown spots was significantly different only after bleaching (p<0.001). Repeated measures ANOVA showed that ΔE between brown spots and adjacent sound enamel did not change significantly in the two subgroups (p>0.05). The results show that for esthetically unfavorable brown spots, using 20% carbamide peroxide with CPP-ACP or resin infiltration can improve the appearance. In general, application of resin infiltration with carbamide peroxide is preferably recommended for improving translucency.

Discoloration of resin composites is considered to be the major factor in esthetic restoration failures. The aim of this study was to evaluate the color stability of resin composites after rebonding with two different adhesive materials. Forty five composite disc samples were divided into three groups (n=15). The surface of specimens was finished by polishing disc and rubber. In group 1, any additional phase was not performed. In group 2, composite discs were etched by %37 orthophosphoric acid, then Margin- bond was used for rebonding. In group 3, the etching procedure was in the same manner used for group 2, but Permaseal was used after etching. After the first phase of spectrophotometric measurement, the specimens were dipped in coffee mix for 3 weeks for aging the specimens. Then the second phase of spectrophotometric evaluation was performed. Collected data was analyzed using one-way ANOVA test followed by Tukey test. P<0.05 was considered as the level of significance. The mean total color difference (∆E) observed in groups 1 to 3 were 1.4±0.34, 5.24±1.51, and 7.44±1.34, respectively. Statistical significant differences were shown between the groups (P<0.001). Rebonding with adhesive materials used in this study did not increase the color stability of composite restorations.

To achive natural and harmonic restoration color, shade matching is a commonly used method in dental practice using shade guides. To prevent infection,shade guides are required to be disinfected. Using of disinfection solutions gradually affect the color of dental equipment. The aim of this study was to evaluate the effect of three disinfectants sodium hypochlorite solution 5/25%, Deconex and Glutar aldeid 2% on the color stability vita Lumin shade guide by using the spectrophotometer. Samples were divide into 4 groups(n=10) one of them as a control group, was excluded. In order to simulate the condition of immersion per one year, they were immersed for 24 hours in disinfectant and for 5 minutes, rinsed with distilled water in ultra sonic machines and washed under the tap water for 30 seconds. Using the spectrophotometer based on CIELab color system, statistical analysis were done using done by one way ANOVA and Dunnett C test.There were significant differences in L(P<0.001) and b(p<0.01) values in all groups as compared to those of control group. In a value there were no significant differences in all of the groups for ∆E(p> 0.05). If we could follow the manufacturer`s recommendations about time and how to use disinfectants, it would prevent clinically perceptible changes in shade guides color.

Color match between the restoration and the patient’s natural teeth has always been a source of concern in esthetic dentistry. One of the reasons for a lack of color match between the restoration and the natural teeth is the type of the alloy used in the metallic structure of the restoration. The aim of this study was to assess and compare the effect of 4 alloys on the color of the overlying porcelain: Degobond 4 from the high noble group، Begopal from the high-palladium group، and Super Cast and Minalux from the nickel-chromium base metal group. In this in vitro study، twenty disks، measuring 2 mm in thickness and 10 mm in diameter، were prepared (5 samples from each alloy). Then Vita 3DMaster 3M2 porcelain was placed on the samples. In addition، 5 control samples، measuring 2 mm in thickness، were prepared from the porcelain. A spectrophotometer was used to determine sample colors، which were evaluated based on CIELAB system. Data was analyzed with one-way ANOVA and Tukey test (α = 0. 05). The four alloys in this study exhibited significant differences in a* and b* values from the control group (p value < 0. 001). The alloy groups did not exhibit any significant differences from each other in a* and b* values (p value > 0. 05). There were significant differences in L* values between Supercast and Begopal (p value = 0. 009) and between Begopal and the control (p value = 0. 013) groups. There were no significant differences in ∆E between the alloys. The type of the alloy has an effect on the final color of porcelain; however، this color difference is clinically acceptable.

Background and Worker's exposure to respirable silica particles and in particular free crystalline silica in the workplace causes some disorders such as silicosis or lung fibrosis. This study was carried out to evaluate the worker's exposure to free crystalline silica particles using the infrared spectrophotometery method in some industries. In this cross sectional study respirable silica dust was collected from worker's breathing zone using a personal sampling device and a cyclone separator with a PVC filter. Silica samples then were analyzed using a infrared spectrophotometery recommended by NIOSH in method number 7602. Mean personal exposure to respirable silica particles within the worker's breathing zone in 4 industries were considerably higher than the threshold limit value recommended by ACGIH. Worker's exposure to crystalline silica particles ranged from 0.03 mgm-3 to 0.57 mgm-3 and there was a significant difference between mean respirable particle concentrations within the worker's breathing zone in these industries. Individuals who are working in asphalt production, foundry work, and sand and gravel mining and brick manufacturing are exposed to crystalline silica particle concentration higher than the standard level. Therefore, engineering and hygiene methods of dust control should be applied for the reduction of exposure and prevention of silica related disorders.

A common procedure in esthetic dentistry is fabrication of metal-ceramic veneer crowns that have proper color match with the patient’s teeth. The aim of this study was to compare color reproduction of the selected color by dental practitioners in dental laboratories by technicians with and without academic education. In this in vitro study a maxillary incisor from a dental model was prepared for a metal-ceramic veneer crown. After impression taking and making a standard framework، 36 impressions were taken for 36 laboratories and two standard metal frameworks were fabricated on each die. Two frameworks were sent to each laboratory. A3 porcelain was requested to be placed on the standard frameworks and glazed. Each specimen was tested with Shadepilot equipment. a*، b* and L* color indexes and DE were determined at incisal، middle and cervical areas of each crown. T-test and linear regression were used for data analysis (α=0. 05). Means and standard deviations of DE of samples in the group without academic education at incisal، middle، and cervical areas were 3. 56±1. 93، 2. 54±2. 40، and in 3. 0±1. 16، respectively; corresponding values in the group with academic education were 5. 6±3. 19، 2. 11±1. 02، and 21. 18±0. 72، respectively. T-test showed significant differences in DE of incisal areas between the two groups (P=0. 003)، with no significant differences in other areas. In this study، there was a significant relationship between job experience and color match accuracy in the incisal region، indicating that technicians with more job، but with no academic education، exhibit more accuracy in reconstructing incisal edge color of metal-ceramic veneer crowns.

Methanol causes so many severe toxicities. Chronic low dose methanol ingestion can cause severe toxicity. There are many unpublished reports from doctors about side effects of toxicity by methanol like blinding in chronic user of herbal essences. Regarding to kinds of herbal essences producing and side effects of its chronic using, probability, there is methanol in the process of making. Therefore we decided to evaluate rate of methanol in various products. In this cross-sectional analytic study, 3 samples of high consumption homemade herbal essences in Arak (Pussy, Mint, Fenugreek, Hedysarum, Dill and Chicory) and 3 samples of the same herbal essences from industrial products with trademarks were gathered. All of them have been analyzed with spectrophotometer in five times. The maximum methanol concentration was related to a sample of industrial Mint (415.04 ppm) and the minimum methanol concentration was related to a sample of handmade Fenugreek (60.26 ppm). There was no significant difference between methanol concentration in handmade and industrial herbal essences. There is probability of methanol toxicity after chronic usage of some herbal essences. Due to lack of maximum permissible concentration for non methanol essences, it is recommended that a cut of point of methanol concentration was determined and inform people about it.