This is a confirmatory study to evaluate the effect of photoinitiator type and concentration, matrix monomer chemical structure, and nanoparticle incorporation on the physical and mechanical properties of an experimental dentin bonding agent.
Materials and methods
Different concentrations of camphorquinone-amine (CQ-A) system, butanedione (BD), and phenylpropanedione (PPD), as photoinitiator, BTDMA, as a comonomer containing carboxylic acid groups, and silica nanoparticles as reinforcing inorganic filler were incorporated into a methacrylate base experimental dental adhesive. The effect of these ingredients, as independent variables, on the shrinkage kinetics, flexural strength and modulus, and microshear bond strength of the adhesives were then investigated. The results were analyzed using one-way ANOVA and Tukey’s post-hoc test at the significance level of 0.05.
Results
The results indicate that the efficiency of CQ-A initiator system is diminished in the presence of the acidic monomer BTDMA while the photopolymerization is efficiently progressed with BD as initiator. PPD shows the lowest efficiency in the photopolymerization of the adhesives. BTDMA as a monomer with the capability of interaction with tooth structure provides adhesive with improved microshear bond strength to dentin. Incorporation of silica nanoparticles at low concentrations enhances the flexural and microshear strength of the dentin bonding agent.
Significance
Understanding the structure–property relationship in dental adhesives may help the material selection in clinical dentistry. The study elucidates the relationship between monomer structure, initiator type, and nanofiller and physical and mechanical properties in dental adhesives. 相似文献
Runx1 is expressed in skeletal elements, but its role in fracture repair has not been analyzed. We created mice with a hypomorphic Runx1 allele (Runx1(L148A) ) and generated Runx1(L148A/-) mice in which >50% of Runx1 activity was abrogated. Runx1(L148A/-) mice were viable but runted. Their growth plates had extended proliferating and hypertrophic zones, and the percentages of Sox9-, Runx2-, and Runx3-positive cells were decreased. Femoral fracture experiments revealed delayed cartilaginous callus formation, and the expression of chondrogenic markers was decreased. Conditional ablation of Runx1 in the mesenchymal progenitor cells of the limb with Prx1-Cre conferred no obvious limb phenotype; however, cartilaginous callus formation was delayed following fracture. Embryonic limb bud-derived mesenchymal cells showed delayed chondrogenesis when the Runx1 allele was deleted ex vivo with adenoviral-expressed Cre. Collectively, our data suggest that Runx1 is required for commitment and differentiation of chondroprogenitor cells into the chondrogenic lineage. 相似文献
A novel low-pressure radio-frequency plasma treatment protocol was developed to achieve the effective through-thickness surface modification of large porous poly (d,l-lactide) (PDLLA) polymer scaffolds using air or water: ammonia plasma treatments. Polymer films were modified as controls. Scanning electron micrographs and maximum bubble point measurements demonstrated that the PDLLA foams have the high porosity, void fraction and interconnected pores required for use as tissue engineering scaffolds. The polymer surface of the virgin polymer does contain acidic functional groups but is hydrophobic.
Following exposure to air or water: ammonia plasma, an increased number of polar functional groups and improved wetting behaviour, i.e. hydrophilicity, of wet surfaces was detected. The number of polar surface functional groups increased (hence the decrease in water contact angles) with increasing exposure time to plasma. The change in surface composition and wettablility of wet polymer constructs was characterised by zeta potential and contact angle measurements. The hydrophobic recovery of the treated PDLLA polymer surfaces was also studied. Storage of the treated polymer constructs in ambient air caused an appreciable hydrophobic recovery, whereas in water only partial hydrophobic recovery occurred. However, in both cases the initial surface characteristics decay as function of time. 相似文献
Among the numerous attempts to integrate tissue engineering concepts into strategies to repair nearly all parts of the body, neuronal repair stands out. This is partially due to the complexity of the nervous anatomical system, its functioning and the inefficiency of conventional repair approaches, which are based on single components of either biomaterials or cells alone. Electrical stimulation has been shown to enhance the nerve regeneration process and this consequently makes the use of electrically conductive polymers very attractive for the construction of scaffolds for nerve tissue engineering. In this review, by taking into consideration the electrical properties of nerve cells and the effect of electrical stimulation on nerve cells, we discuss the most commonly utilized conductive polymers, polypyrrole (PPy) and polyaniline (PANI), along with their design and modifications, thus making them suitable scaffolds for nerve tissue engineering. Other electrospun, composite, conductive scaffolds, such as PANI/gelatin and PPy/poly(ε-caprolactone), with or without electrical stimulation, are also discussed. Different procedures of electrical stimulation which have been used in tissue engineering, with examples on their specific applications in tissue engineering, are also discussed. 相似文献
BACKGROUND: Clinical trials in children concerning Helicobacter pylori eradication treatments are scarce. The purpose of this study was to assess the efficacy of proton pump inhibitor (PPI)-based triple therapy using PPI, amoxicillin and clarithromycin in Iranian children. We also evaluated the efficacy of quadruple therapy with PPI, metronidazole, amoxicilin and bismuth citrate in Iranian children. METHODS: This was a randomized clinical trial performed in Emam Khomeini Hospital between 2003 and 2004. Patients with confirmed H. pylori infection by histology were divided into two groups in a randomized 1:1 scheme: the triple regimen group (omeprazole, clarithromycin and amoxicillin for 10 days) and the quadruple regimen group (omeprazole, amoxicillin, metronidazole and bismuth citrate for 10 days). The eradication was assessed by the C-urea breath test 4 weeks after the end of treatment and analyzed by per-protocol and intention-to-treat approaches. RESULTS: One hundred and twenty-two patients (mean age 12.36+/-3.06 years) were entered into the study. Only 100 patients completed the study (50 patients in each regimen group). The eradication rates by triple therapy were 92% and 75.5% for the "per-protocol" and "intention-to-treat" approaches, respectively. In the quadruple regimen group, the eradication rates were 84% by the per-protocol approach and 68.8% in the intention-to-treat approach. Symptom responses to therapy were reported in all patients with successful eradication (88% of all patients). CONCLUSION: With regard to recent recommendations, we also suggest PPI, amoxicillin and clarithromycin triple therapy as a first-line eradication treatment, and quadruple therapies as a second-line option, in Iranian children. 相似文献