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"nBackground and Aim: In spite of the achievements in the field of dental adhesives, we are facing challenges with dentine bonding resistance, strength and stability. According to recent studies the role of MMP inhibitors in association with bonding,s persistence and leakage reduction and restoration,s persistence is important. The aim of this study was to investigate the effect of doxycycline as a MMP inhibitor on the degree of conversion (DC) of an experimental dental adhesive. "nMaterials and Methods: In this experimental study, a new dental adhesive blend was prepared by mixing doxycycline monohydrate (in concentrations of 0.0, 0.25, 0.5, and 1 wt.%) with monomers. The monomers were composed of 12% Bis-GMA and 10% TMPTMA, 28% HEMA, and 50% Ethanol by weight for all groups. Comphorquinone and amines were chosen as photo initiator system. Degree of conversion of all adhesives was measured using FTIR spectroscopy. The results were analyzed using one-way ANOVA and Tukey post hoc tests. "nResults: The results showed that addition of 0.25, 0.5, and 1 weight percent doxycycline did not significantly reduce the DC of the adhesives compared to 0.0% control group (p>0.05%). "nConclusion: According to the results of this study, adding doxycycline to the adhesives did not adversely affect the DC.

"nBackground and Aim: Nonmetallic tooth- colored posts adhere to canal walls by dentin bonding agents and resin cements. Better retention and proper distribution of stress result from enough and proper bonding. The purpose of this study was to evaluate bond strength of D.T. Light - post with two different resin cements (self-cure & dual-cure) and to investigate the effect of irrigating solutions applied in root canal on bond strength of the resin cements and D.T.Light- post to root canal wall. "nMaterials and Methods: In this experimental study 40 single root teeth (maxillary canine & central) were selected and stored in 0.1% thymol solution for one week and transferred to distilled water. The teeth were decoronated 2mm above CEJ. The canal space was mechanically enlarged using k-files (up to # 70). The teeth were randomly divided into two groups. The first group was irrigated with 2.6% NaOCl, and the second was irrigated with normal saline. After drying, the teeth were filled with gutta percha cones using lateral condensing method. After two weeks the post space was prepared and D.T.Light- post was inserted in each subgroup using self or dual-cure cements according to manufacturer's instructions. After thermocycling, the apical part was cut 1cm below CEJ. The remained length was divided into 9 equal sequential sections. Each section was submitted to shear push-out test in universal testing machine. Statistical analysis of the bond strength data was performed using ANOVA and post hoc tests with p

Anaerobic adhesives are polymerized and hardened rapidly through a free radical mechanism when placed between two metallic surfaces. The conducted investigations from 1960 have studied polymerization rate in the presence of different metallic ions, their breakdown speed using polarography techniques, and also the common use of cumene hydro-peroxide as an initiator. In order to investigate the effect of initiator type and concentration on the setting time of these adhesives, four different types of initiators in concentrations of 1–3 parts per hundred resin (phr) were incorporated into the monomer. The initiators were cumene hydroperoxide (CHP), methyl ethyl ketone peroxide, tert-butyl hydroperoxide, and benzoyl peroxide. The metal salt used was copper (II) saccharin. The obtained results indicated that the setting time in the methacrylate compositions depends not only on the initiator concentration, but also on its relative amount with respect to the metal ion, and some other factors such as monomer type, and stoichiometric relation between the metal ion and the accelerator—here, dimethyl p-toluidine, which was assumed to have an important role in the setting process. Finally, CHP was identified as the most appropriate initiator with an optimum value of 2 phr. [ABSTRACT FROM PUBLISHER]

The aim of this study was to investigate physical and mechanical properties of graphene oxide (GO)/polyethersulfone (PES) nanocomposite films. The films were produced by solution casting method. The mechanical properties of composite films were evaluated by tensile test. A significant enhancement in the mechanical properties of neat PES films was obtained incorporating a small amount of GO loading (0.05-1 wt.%). The highest tensile strength was observed at 1 wt.% of GO. Comparisons were made between experimental data and the Halpin-Tsai model predictions for the tensile strength and modulus of GO/PES composites. The effect of an orientation factor on model predictions was also acquired. The hydrophilicity of the nanocomposite was evaluated by assessing contact angle and enhanced wet ability of the films was obtained with increasing the amount of GO up to 1%. The morphology of the nanocomposites was investigated using scanning electron microscopy and transmission electron microscopy and the results revealed a good dispersion of GO in the PES matrix. The thermal behavior of the composite was also studied. Thermal stability of composites was increased by adding the GO. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective: An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs) claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams. Materials and Methods: In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (American Orthodontics, GAC and Ortho-Technology). Each brand was divided into two groups with respect to their claimed characteristics (with or without memory). Each sample was stretched to twice its original length and kept constant in 37°C distilled water. Force-extension diagrams were drawn by universal testing machine at 0,1,8,24,72 hours and 1, 2, 4-week intervals. Additionally, the amounts of elongation required to deliver 200 g force were calculated. To compare the results, ANOVA and Tukey tests were performed. Results: Force-decay rate was significantly different between traditional and memory chains (p<0.05). For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4 weeeks. The memory chains demonstrated more constant force and retained 60% of the force. The maximum amount of elongation required to deliver 200 g force belonged to American Orthodontics memory chains (61.9% after 24hr) and the minimum to Ortho-Technology ECs (23.4% initially). Conclusion: Memory chains exhibited superior mechanical properties compared to traditional ones. For delivering the same force, memory chains required more elongation. Memory chains of GAC and American Orthodontics showed better characteristics among all chains. [ABSTRACT FROM AUTHOR]

Statement of Problem: Polymerization shrinkage is one of the major problems of the current dental composites and it can cause marginal gap and post-operative sensivity. Purpose: The purpose of this study was to investigate the effect of nanoporous fillers on the polymerization shrinkage and degree of conversion of an experimental dental composite in three different curing modes and also comparing the results of it with another experimental composite containing conventional fillers. Methods and Material: In this study, the experimental composite was prepared by mixing the silane treated fillers with monomers. The monomers consisted of 70% Bis-GMA and 30% TEG DMA by weight. The experimental composite was divided into two groups according to their filler type, i.e. conventional micro-hybrid and nanoporous. In order to make nanoporous fillers, the fillers were sintered in 1300°c and grinded Camphorquinon and DMA EMA were used as initiator-accelerator systems. Polymerization shrinkage was measured using bonded disc method in three curing modes (High Intensity, Ramp, Standard). The degree of convention was measured using FTIR spectroscopy. Result: The results showed that the nanoporous fillers have a positive effect on the reduction of polymerization shrinkage strain. No significant difference was found in polymerization shrinkage of the three curing modes. Neither the type of fillers nor the mode of cure had an effect on the degree of conversion. Conclusion: Lower polymerization shrinkage strain can be achieved by using nanoporous fillers. The mode of cure does not affect the polymerization shrinkage. [ABSTRACT FROM AUTHOR]

Background and Aim: In spite of the achievements in the field of dental adhesives, we are facing challenges with dentine bonding resistance, strength and stability. According to recent studies the role of MMP inhibitors in association with bonding,s persistence and leakage reduction and restoration,s persistence is important. The aim of this study was to investigate the effect of doxycycline as a MMP inhibitor on the degree of conversion (DC) of an experimental dental adhesive. Materials and Methods: In this experimental study, a new dental adhesive blend was prepared by mixing doxycycline monohydrate (in concentrations of 0.0, 0.25, 0.5, and 1 wt.%) with monomers. The monomers were composed of 12% Bis-GMA and 10% TMPTMA, 28% HEMA, and 50% Ethanol by weight for all groups. Comphorquinone and amines were chosen as photo initiator system. Degree of conversion of all adhesives was measured using FTIR spectroscopy. The results were analyzed using one-way ANOVA and Tukey post hoc tests. Results: The results showed that addition of 0.25, 0.5, and 1 weight percent doxycycline did not significantly reduce the DC of the adhesives compared to 0.0% control group (p>0.05%). Conclusion: According to the results of this study, adding doxycycline to the adhesives did not adversely affect the DC. [ABSTRACT FROM AUTHOR]

Horse anti-dog lymphocyte serum was found to suppress the immune response of dogs normally resulting from the injection of Salmonella typhi vaccine. Normal antibody levels of the dogs against Shigella dysenteriae were unaffected, however, by the anti-lymphocyte serum. The results suggest, therefore, that the natural antibodies may arise by a population of cells or by mechanisms different from those which produce antibodies as a result of deliberate antigenic stimulation.

Background and Aim: Inadequate polymerization is one of the main causes of composite restoration failure .the aim of this in vitro study was to evaluate the degree of conversion of bulk fill composites through using FTIR. Materials and Methods: in this experimental study ,.10 disk shape specimen from each material contain X-tra base (Voco, Germany ) and X-tra fil (Voco, Germany ) composites were made in dimension of 2 mm diameter and 4 mm height . The curing procedure was done by LED Turbo (Apoza, Japan ) with intensity of 800mw/cm 2 for 20 seconds .Then 1mm from the top and 1mm from the base of composite specimen cut with diamond disk and degree of polymerization were evaluated with Fourier transform infrared spectrophotometer (FTIR).The values obtained were analysis by one way ANOVA. Results: Although differences in degree of polymerization of X-tra base and X-tra fil in 1mm of top and bottom of composites were significant( p˂0/001) but the mean percentage value of polymerization on top and bottom surfaces for both composites were higher than acceptable range( DC =55%) Conclusion: Based on recent results of this study, polymerization degree of all composites clinically were acceptable. Although degree of polymerization of X-tra fil was lower than X-tra base. [ABSTRACT FROM AUTHOR]