فهرست مطالب m.h. salari

Shade guide discoloration after disinfection can interfere with the appropriate color selection for dental restorations. Since one of the most important issues for patients is the color of the final restoration, the discoloration of shade guides due to disinfectants will be important. Infection control is a definite and important matter in dentistry. Due to the contradictory results of studies on the effect of disinfectants on shade guide discoloration, this study aimed to examine the discoloration of the Vita classical shade guide by glutaraldehyde disinfectant. 

In this experimental study, samples of A4, B4, C4, and D4 colors were selected from the Vitapan classical shade guide, 10 pieces each (40 samples in total). Three samples of each color were immersed in distilled water as a control while the other seven were immersed in a 2% glutaraldehyde disinfectant solution. The shade pilot spectrophotometer was used for colorimetry, which was performed at baseline and 24, 48, and 72 hours after the immersion. The color of the samples was evaluated based on the CIE Lab system. The data were analyzed with two-way analysis of variance (ANOVA) and Tukeychr('39')s test.

The rate of color change (ΔE) of the samples was higher in the glutaraldehyde group than in distilled water (P<0.05). In addition, color change in both groups showed a significant difference at different times (P<0.05).

The Vitapan classical color samples discolor by immersion in 2% glutaraldehyde disinfectant after 24, 48, and 72 hours, but this color change is not clinically detectable (ΔE<1).

This study aimed to assess the effect of G-Bond and Z-Prime Plus on fracture resistance of prefabricated zirconia posts bonded to root canal walls.

This in-vitro experimental study evaluated 22 mandibular premolars with equal diameter and length. The teeth were cut at the cementoenamel junction (CEJ), underwent root canal treatment, and were randomly divided into two groups (n=11). One tooth from each group served as a control. Post space was prepared in the remaining teeth with a 10-mm length. Intracanal dentin was then etched, rinsed, and dried. Panavia F2 resin cement was applied to the canal. Z-Prime Plus and G-Bond were applied to the surfaces of zirconia posts in groups 1 and 2, respectively, and the posts were then cemented into the canals. The cores were built-up using Photo Core resin composite. The teeth underwent a compressive force applied to the central fossa of the core along their longitudinal axes at a crosshead speed of 0.5 mm/minute. The load at fracture was recorded. Data were analyzed using t-test considering their normal distribution.

The mean fracture resistance was 1094.2±328.0 N with G-Bond and 912.6±373.0 N with Z-Prime Plus; the difference was not significant (P=0.4).

G-Bond and Z-Prime Plus were not significantly different in fracture resistance of zirconia posts bonded to root canal walls. However, G-Bond is recommended for this purpose since it had a lower coefficient of variation (CV) and slightly higher fracture resistance.

Due to the importance of the bond strength between zirconia core (ZC) and porcelain veneer (PV) as well as the paradox about the functionality of sandblasting on the solidity between those layers, this research aimed to evaluate the effect of sandblasting on the shear bond strength (SBS) between ZC and PV. After preparing 20 zirconia discs (7 mm × 3 mm) in this experimental study, they were randomly divided into two groups of case and control. In the case group, sandblasting with 120-μm aluminum oxide particles (Al2O3) was performed under 3.5-bar pressure at 10 mm distance from the zirconia surface for 15 seconds. Next, all the samples were cleaned with ultrasonic and 96% isopropyl alcohol for 3 minutes as well as steam cleaning for 10 seconds. Then, the samples were veneered with porcelain (3 mm × 5 mm). SBS was assessed using a universal testing machine. After data collection, the mean and standard deviation (SD) were calculated and analyzed using T-test. The SBS between ZC and PV was 62.56±8.35 MPa in the case group (after sandblasting) and 94.62±7.69 MPa in the control group. The SBS showed a significant statistical difference between the two groups (P=0.001). The result of this research indicated that sandblasting reduces the SBS between ZC and PV. Considering the limitations and the methodology of the study, the hypothesis regarding the positive impact of sandblasting on SBS was not proven.

Inherited bleeding disorder is a disease due to deficiency in clotting factors or platelets. Replacement therapy of unscreened blood and blood products or unviricidal concentrated clotting factors would expose these patients to risk of acquired hepatitis C. The aim of this study was to determine the seroprevalence of hepatitis C virus and related risk factors among bleeding disorder patients in Yazd province. This cross-sectional study was performed in Yazd province in summer 2006 using census method. Following data collection through questionnaires, blood samples were taken from 77 (82.8%) patients. Plasma samples were tested for the presence of anti-HCV antibody via a third-generation ELISA kit. To exclude false positive cases, ELISA positive samples were re-tested by the confirmatory third generation RIBA test. The assessment of risk factors was done from the information analysis of both the questionnaires and test results by Chi-square test and multivariate logistic regression analysis, using SPSS 11.5 statistic software. The frequency of anti-HCV antibody was found in 38 (49.4%) patients. Chi-square test showed a statistically significant relationship between the severe form of the disease (in terms of blood products needed) (P<0.001), treatment duration of more than 121 months (P<0.001) and family history to HCV (P<0.05) antibody positivity. Successful execution of the screening of the blood and blood products as well as more scrutiny in preparing concentrated factors have been led to a remarkable decrease in the new infections among the recipients of these products in Yazd province.

Abstract: Enterococci are members of the normal gut flora and released into the environment via sewage outlets, where they can survive for long times. Infections with high-level gentamicin resistant (HLGR) enterococci are emerg­ing worldwide. HLGR enterococci have developed a resistance to most antibiotics commonly used for enterococcal in­fec­tions therefore; treatment of infections caused by HLGR enterococci is difficult. The present study investigated the dis­tribution and antibiotic resistance of HLGR Enterococcus faecium and E. faecalis isolates from raw wastewater sam­ples in Tehran. Raw wastewater samples were collected during the period from November 2006 to May 2007 at 3 sewage treat­ment plants located in different parts of Tehran. All 90 HLGR enterococcal isolates were identified to the species level by biochemical and PCR assays and subjected to antibiotic susceptibility testing. Sixty four percent (58 of 90) of isolates were E. faecium and 29%(26 of 90) of them were E. faecalis. The high­est level of antibiotic resistance was observed with erythromycin (63%), co-trimoxazole (69%) and tetracycline (92%) for E.faecalis and with erythromycin (97%), ciprofloxacin (47%), co-trimoxazole (45.5%) and tetracycline (47%) for E. faecium. Multiresistance against 3 to 4 antimicrobial was present in 27.5% and 15.5% of the isolates, re­spectively. HLGR E. faecium were more commonly found than E. faecalis. Species identification of HLGR entero­cocci enables us to assess species-specific antibiotic susceptibility patterns in our area. The present study reviled that HLGR E. faecalis remained more susceptible than E. faecium against the usual first-line and alternative treatments.

Abstract: Backround: Clostridium difficile is the most common cause of nosocomial diarrhea. It is usually a consequence of antibi­otic treatment, but sporadic cases can occur. The purpose of this study was to investigate five tissue culture monolayers sen­sitivity in detection of C. difficile-toxin. A total of 402 stool samples from patients with nosocomial diarrhea hospitalized in three hospitals of Tehran Uni­versity of Medical Sciences (TUMS) were collected. The samples were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) and incubated in anaerobic conditions, at 37 °C for 4 days. Isolates were characterized to species level by con­ventional biochemical tests. Bacterial cytotoxicity was assayed on five tissue culture monolayers. Our findings show that of the total patients, 24 toxigenic C. difficile (6%) were isolated. All 24 C. difficile toxins showed cytotoxic effect at ³ 1:10 dilution on Hela, Hep2, Vero, McCoy and Mdck cells after 16, 20, 24, 24 and 30 hours, re­spectively. C. difficile toxin showed cytotoxic effect at ³ 1:100 dilutions only on Hela cell monolayer after 48 hours. Hela cell monolayer may be a satisfactory substitute for the detection of C. difficile toxin in clinical specimens.

Clostridium difficult is an identified cause of antibiotic-associated diarrhea, antibiotic-associated colitis, pseudomembranous colitis and nosocomial diarrhea. The purpose of this study was to investigate the prevalence of nosocomial C. difficile-associated diarrhea in Tehran University of Medical Science Hospitals. In this study a total of 942 stool samples from patients with nosocomial diarrhea that were hospitalized in Imam Khomeini hospital, Shariati hospital and Children clinical center were collected. The samples were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) and incubated in anaerobic conditions, at 37 °C for 5 days. Isolated C. difficile by conventional biochemical tests, bacterial cytotoxicity by Vero tissue culture and antimicrobial sensitivity to antibiotics by Kirby Bauer method (disk diffusion) were investigated. Of the total patients, 57 Toxigenic C. difficile (6.1%) were isolated. Results of statistical analysis show significant differences between the rate of isolated Toxigenic C. difficile and age group of patients (P< 0.05). Among the units of selected hospitals, Toxigenic C. difficile was isolated most frequently in gastroenterology of Children clinical center. Meanwhile, the isolated Toxigenic C. difficile were sensitive to vancomycin, Chloramphenicol and ceftriaxone. Our findings show that, Toxigenic C. difficile was found in 6.1% hospitalized patients. Therefore, further studies to evaluate the role of Toxigenic C. difficile in nosocomial diarrhea processes, ecological and pathogenic terms by culture, Tissue culture and molecular methodes are suggested.

Abstract: Clostridium difficile is a frequently identified cause of nosocomial gastrointestinal disease. It has been proved to be a causative agent in antibiotic-associated diarrhea, antibiotic-associated colitis, and pseudomembraneous colitis. This study was aimed to determine the prevalence of C.difficile- associated diarrhea in hospitalized patients with nosocomial diarrhea. The 942 hospitalized patients stool samples with nosocomial diarrhea were collected at three hospitals in Tehran from Dec 2002 to Feb 2004.All the stool samples were cultured and in 97 (prevalence: 10.9%) samples grew C.difficile that 57 (prevalence: 6.1%) isolates were toxigenic by cytotoxicity assay and so 57 patients had C.difficile- associated diarrhea. Results of statistical analysis showed significant difference between the rate of C.difficile associated diarrhea and the patients ages (P<0.05).

Tuberculosis is a continuous threat for health in all parts of the world. An estimated one-third of the world, s population is infected with the Mycobacterium tuberculosis and 7 to 8 million people develop TB disease each year. The purpose of this study was to investigate the rate of tuberculosis in the townships of Yazd province, Iran. During the study period (1997-1999), 3885 suspected tuberculosis patients (1820 males and 2065 females; aged 8-85 years) who had been referred to the Yazd referral polyclinic were investigated by Ziehl Neelsen staining and culture method and questionnaire was completed for each subject. Then, Collected data were analyzed by statistical package for social science (SPSS) and chi-square program. The results show that, of the total suspected tuberculosis, 604 cases were found to be positive for tuberculosis. The average annual rate of tuberculosis was 26.8 cases per 100000 population (23.1/100000 males and 31/100000 females). The highest and lowest rates of tuberculosis were observed among Sadough (78.1/100000) and Abarkouh townships population (19.8/100000) and also among age group ≥ 50 years old (111/100000) and < 10 years old (7/100000), respectively. The average annual rates of pulmonary and extra-pulmonary tuberculosis in Yazd province were 152 cases (20.2%) and 48 cases (6.4%), respectively. It seems that, despite the efforts, which have been done for prevention, diagnosis and treatment of patients with tuberculosis, it is still considered as a threat for health in the Yazd province, Iran.

Mycoplasma and Ureaplasma species are the most serious contaminants of cell cultures and this remains one of the major problem encountered in biological research using cell cultures. The aim of this study was to investigate the rate of Mycoplasma and Ureaplasma species as contaminats of cell cultures. A total of 100 different cell culture specimens including, R228, Hela, Vero, MDCK, L20, RD and Hep2 were collected. Then the specimens were investigated by culture method and biochemical tests. The rate of contaminant cell culture specimens was 32%. The highest and lowest rate of contamination was observed among Hela cell culture (25%) and R238 cell culture (0%), respectively. Moreover, the results of 2 statistical analysis test, showed significant difference between contamination rate and kind of cell culture (p = 0/001). It is concluded that Mycoplasma and Ureaplasma species are the most common source of further contamination of cell cultures.

Brucellosis has remained a great problem of health in most of countries, which have failed in control of zoonosis infections. This disease is caused by species of Brucella and usually is transferred from animals to humans. The purpose of this study was to investigate the seroprevalence of brucellosis among animal farmers of Yazd province. In this descriptive study, 933 animal farmers were investigated by serological tests and blood culture method. Then the data were analyzed by SPPS statistical program. The results showed that the frequency distribution of seropositive cases by MAT and STAT were 35 (3.2%); 25 (2.7%) males and 10 (1.1%) females. The highest and lowest incidences of seropositive cases were among age group of 21-30 (1%) and more than 60 (0.3%) years old, respectively. Of the 35 seropositive cases, 2MET positive were 5 (0.5%), while all blood cultures were negative.