[Heterologous expression of salmon calcitonin in Escherichia coli]

Background and Objective: Calcitonin is a small peptide hormone including 32 amino acids and 3.4 KD molecular weight which is produced by the parafollicular cells of the thyroid gland in respond to increasing calcium ions in serum. This peptide is used for adjuvant therapy of osteoporosis, Paget's disease and hypercalcemic shock. In this study, the heterologuse expression of calcitonin was done in Escherichia coli

Methods: In this experimental study, the thioredoxin fusion partner was added to n-terminal of the Salmon calciton in order to increase its stability by the synthetic biology. The recombinant construct was transformed and over expressed into Escherichia coli BL21 [DE3] host cell

Results: SDS-PAGE analysis showed the over expression of recombinant protein after IPTG induction

Conclusion: In this study, the construct including fused Salmon calcitonin gene with thioredoxin was cloned. The SDS-PAGE result showed the stable expression of fused calcitonin

comparative study on micro hardness and structural changes of dentin floor cavity prepared by ER: YAG laser irradiation and mechanical bur

Statement of Problem: Laser irradiation makes structural and chemical changes on the dental hard tissues. These changes alter the level of solubility and permeability of dentin

Purpose: The aim of this study was to compare the microhardness and the structural changes in the dentin cavity floor prepared with Er: YAG laser and bur

Material and Methods: In this experimental study, fifteen intact human molars were selected. Two square cavities were prepared on the buccal and lingual surfaces of each tooth. One side was randomly prepared by Er:YAG laser and the other side by bur

The specimens were divided into two halves. Consequently, there were 30 samples in every group. One half was assigned for the Vickers's hardness test and the other one, for determination of Ca and P percentage and atomic elements analysis. The data were analyzed by Paired T-tests through SPSS16 [ alpha

Results: The means and the standard deviation of the microhardness were 69.77+/-25.62 and 51.33+/-9.31 Kg/mm2 in the laser and bur groups, respectively. Statistical analysis showed significant differences between the two groups [p=0.017]. Weight percentage of calcium in the laser cavity [65.5] was less than the bur cavities [68.21] and the difference was significant [p= 0.037]

Conclusion: The hardness of dentin in laser group was higher than the bur group because of the higher mineral content of the dentin. The hardness and the mineral content of dentin are important factors in the bonding effectiveness of the dental materials so with laser cavity preparation, good mineral substrate are available for a better bonding

[Comparison of chlorhexidine and sodium hypochlorite effect as intracanal irrigants on pain and swelling after root canal therapy in teeth with necrotic pulp]

Post endodontic treatment pain and swelling or both is named as Flare-up which is one of the problems after root canal therapy. This problem is particulary important in necrotic teeth because of infiltration of bacterial agents into the periapical region. Adequate and appropriate irrigation of canal removes intracanal microganisms, debris and infected agents from canal space and decreases the incidence of pain and swelling. Sodium hypochlorite is one of the most effective antibacterial irrigants which dissolves vital and non vital tissues. Chlorhexidine is another irrigant that has antibacterial characteristics. The aim of this study was comparison between the incidence of Flare-up after using chlorhexidine and sodium hypochlorite as irrigatns in root canal therapy of necrotic pulp. In this clinical trial study, 50 patients with single canal necrotic pulp without any symptoms were selected and were divided into two groups of 25. In any group, after isolation and access preparation, canals were prepared using rotary Race files. Canals were then irrigated with chlorhexidine 0.2% and sodium hypochlorite 2.5% and were finally obturated by lateral condensation. A questionnaire was given to the patients to fill the amount of their experienced pain using a visual analogue scale and swelling with a scale with 4 degrees. Patients were followed for 48 hours. The data were analyzed by Mann Whitney, Wilcoxon and Kruskal-Wallis tests. There was no significant difference between irrigant solutions in decreasing the amount of pain and swelling after endodontic treatment. No significant relationship was detected between amount of pain and swelling, and age and sex. Flare-up was observed more in maxilla compared to mandible. According to less toxicity effect of chlorhexidine, sodium hypochlorite can be replaced by chlorhexidine