Color stability of two bulk-fill composite resins

Objective: Bulk-fill composites are a group of composite resins designed for easy and fast filling of large cavities. This study aimed to assess the color stability of bulk-fill composites subjected to xenon radiation and evaluate their color change [[delta]E] following polymerization

Methods: In this in vitro experimental study, 30 specimens [4mm in height and 8mm in diameter] were fabricated of x-traFil and Tetric N-Ceram universal color bulk-fill composites and A2 shade of Grandio composite [as control]. Bulk-fill composites were placed in the mold in 4mm thickness according to the manufacturers' instructions. In the control group, composite was applied to the mold in two layers each with 2mm thickness. Tetric and Grandio composites were cured for 20 seconds and x-traFil was cured for 10 seconds with a LED light-curing unit. A total of 15 specimens [five of each composite] were used for each test. For assessment of color change due to polymerization, L[asterisk], a[asterisk] and b[asterisk] color parameters were measured before and immediately after polymerization and also 30 days after immersion in distilled water in an incubator at 37[degree sign] and 70% humidity using a spectroradiometer. For xenon test, the specimens were subjected to color analysis after 48 hours of storage in distilled water. Next, they were subjected to xenon lamp radiation in xenon environment chamber for 122 hours at 22[degree sign] and 25% humidity and then the color parameters were measured again. The mean and standard deviation [SD] of all values were calculated. One-way and repeated measures ANOVA were used to compare [delta]E and [delta]L among the groups. Tukey's HSD test was used for pairwise comparisons

Results: The value of [delta]E immediately after polymerization was the lowest for Grandio [4.91] and the highest for Tetric [9.44]. Thirty days after the polymerization, [delta]E was the lowest in Grandio [3.07] and the highest in Tetric [9.27]; [delta]E showed a decreasing trend over time in all specimens. Under xenon light radiation, Grandio showed the lowest [1.50] and Tetric showed the highest [delta]E [11.15]

Conclusion: Following polymerization and under xenon lamp radiation, [delta]E of conventional composite was less than that of bulk-fill composites

Immune reactivity of Brucella melitensis-vaccinated rabbit serum with recombinant Omp31 and DnaK proteins

Brucella melitensis infection is still a major health problem for human and cattle in developing countries and the Middle East. In this study, in order to screen immunogenic candidate antigens for the development of a Brucella subunit vaccine, a cytoplasmic protein [DnaK] and an outer membrane protein [Omp31] of B. melitensis were cloned, expressed in E.coli BL21 and then purified using Ni-NTA agarose. Immunized serum was prepared from a rabbit inoculated with attenuated B. melitensis. It was proved that immunized serum contains antibodies against recombinant Omp31 [rOmp31] and DnaK [rDnaK] by Western blot and ELISA assays. The results may suggest the importance of these proteins as subunit vaccines against B. melitensis as well as targets for immunotherapy

Efficacy of experimental hydrofluoric acid [HF] on bond strength and microleakage of composite-porcelain interface

The aim of this study was to evaluate the quality of an experimental hydrofluoric acid [HF] for preparation of porcelain and to compare it with two commercial hydrofluoric acids in Iranian trademark. A- Evaluation of etch pattern of experimental HF using scanning electron microscope [SEM]: 6 feldespathic discs were divided into 3 groups. Each group was etched with related HF [experimental, Ultradent and Kimia] for 1 minute. SEM images were recorded at 3 magnifications. B- Bond strength test: 18 feldespathic discs were considered for each acidic group. Then the porcelain surfaces were etched and bonded to composite with unfilled resin. Consequently, the microshear test was done. C- Microleakage test: 54 discs were divided into 3 groups [n=18]. Then the porcelain surfaces were etched and bonded to composite with unfilled resin and finally observed under stereomicroscope. The data were analyzed with one-way ANOVA and Smirnov tests. SEM analysis showed no difference between groups in terms of etch pattern. Microshear bond strength values for experimental, Kimia, and Ultradent HF were 28.53 [ +/- 4.92], 28.21 [ +/- 6.61], and 26.14 [ +/- 7.61] MPa, respectively. There was no significant difference between the bond strength of test groups [P<0.05]. Furthermore, no significant difference was found between the microleakage of test groups [P>0.05]. Quality of experimental HF in terms of etch pattern, microshear bond strength and microleakage of composite/porcelain interface was similar to that of two commercial hydrofluoric acids

[ identification of nocardia in BAL specimens of bronchoscopic patients by using classical and molecular methods]

Nocardiosis is a rare and potentially life-threatening infection caused by several species of the Nocardia genus. The objective of this study was to develop and evaluate a rapid and new method to clinically identify relevant Nocardia species. Rapid and accurate diagnosis of Nocardia species is essential for the treatment of severe infections and prevention of cerebral abscess. One hundred and eighty patients, 103 [57.22%] male and 77 [42.78%] female, with severe symptomatic pulmonary infection were studied in the course of a 12-month period in Dr. Shariati Teaching Hospital affiliated to Tehran University of Medical Sciences in 2010. The specimens were cultured and identified using microbiological and biochemical tests. Polymerase chain reaction [PCR] was used to directly identify the organism in the broncoalveolar lavage samples collected from the patients. NG1 and NG2 primers were used to amplify a Nocardia genus-specific 598-bp fragment of 16S rRNA. Nineteen samples [10.56%] were positive with PCR and 5 samples [2.78%] with conventional methods. All samples with positive cultures were also positive by PCR. The results of this study showed that PCR has a high sensitivity and accuracy for the detection of Nocardia compared with culture and biochemical tests. Considering the rapidity, precision, high sensitivity and specificity of molecular techniques, use of these techniques is suggested in conjunction with conventional methods for the detection of Nocardia phenotypes in clinical laboratories and research centers

Cloning, expression and purification of Pwo polymerase from Pyrococcus woesei

Pyrococcus woesei is a hyperthermophilic archaea and produces a heat stable polymerase [Pwo polymerase] that has proofreading activity. In this study, this microorganism was cultured, its DNA was extracted and the pwo gene polymerase was cloned, expressed and purified. The DNA sequence of the cloned gene was verified by sequencing. The pwo polymerase gene consists of 2,328 bps [775 amino acids with about 90 kD molecular weight]. Cloning was done by GATEWAY Cloning System and for purification of recombinant protein; His6x-Tag was added to the C-terminus of the recombinant protein. We could purify Pwo polymerase enzyme by Ni-NTA resin. PCR assay showed that Pwo polymerase activity is comparable to a commercial Pfu polymerase activity