Correction to: Cure kinetic study of methacrylate-POSS copolymers for ocular Lens.

The original version of this article unfortunately contained a mistake: the spelling of the Ebrahim Gafar-Zadehs' name was incorrect. The corrected name is given above.

Cure kinetic study of methacrylate-POSS copolymers for ocular lens.

The physical, mechanical and biological properties of multicomponent acrylate-based hard lenses are directly influenced by degree of conversion achieved during copolymerization. In this research, polyhedral oligomeric silsesquioxane (POSS) acrylate is introduced into the polymer backbone in combination with hydroxyethyl methacrylate, dimethyl itaconate, methyl methacrylate, 3-(trimethoxysilyl) propyl methacrylate and triethylene glycol dimethacrylate in free-radical bulk polymerization. Kinetics of curing process was investigated by two techniques: differential scanning calorimetry and FTIR spectroscopy. Reaction kinetics in free-radical bulk polymerization of the system was studied by isothermal DSC performed at 65, 75, 85, and 95 °C using different quantities of initiator. Three compounds were prepared in different concentrations (0.2, 0.4 and 0.6 mol%) of 2,2'-azobisisobutyronitrile as initiator. Conversion rate was calculated as a function of time using data obtained from DSC measurements. The kinetic parameters of the reaction such as reaction constants, reaction orders and activation energies were obtained from the isothermal DSC data according to the autocatalytic model developed by Kamal and Sourour. The results showed that the experimental values were in good agreement with theoretically estimated values and our results may suggest that the polymerization reaction of this system is well described by Kamal's model. Cytotoxicity results, performed on extracts 28 days after PBS incubation, showed no toxicity of the materials extracted from the lenses indicating that they can be considered as safe materials in ocular lens applications. The viability and proliferation of L929 fibroblast cells in extracting media were followed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and they may have a great potential as ideal supporting lens in people who suffer from keratoconus disease.

Force-degradation pattern of six different orthodontic elastomeric chains.

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.

Photo-crosslinkable cyanoacrylate bioadhesive: shrinkage kinetics, dynamic mechanical properties, and biocompatibility of adhesives containing TMPTMA and POSS nanostructures as crosslinking agents.

The study investigates the photo-polymerization shrinkage behavior, dynamic mechanical properties, and biocompatibility of cyanoacrylate bioadhesives containing POSS nanostructures and TMPTMA as crosslinking agents. Adhesives containing 2-octyl cyanoacrylate (2-OCA) and different percentages of POSS nanostructures and TMPTMA as crosslinking agents were prepared. The 1-phenyl-1, 2-propanedione (PPD) was incorporated as photo-initiator into the adhesive in 1.5, 3, and 4 wt %. The shrinkage strain of the specimens was measured using bonded-disk technique. Shrinkage strain, shrinkage strain rate, maximum and time at maximum shrinkage strain rate were measured and compared. Mechanical properties of the adhesives were also studied using dynamic mechanical thermal analysis (DMTA). Biocompatibility of the adhesives was examined by MTT method. The results showed that shrinkage strain increased with increasing the initiator concentration up to 3 wt % in POSS-containing and 1.5 wt % in TMPTMA-containing specimens and plateaued out at higher concentrations. By increasing the crosslinking agent, shrinkage strain, and shrinkage strain rate increased and the time at maximum shrinkage strain rate decreased. The study indicates that the incorporation of crosslinking agents into the cyanoacrylate adhesives resulted in improved mechanical properties. Preliminary MTT studies also revealed better biocompatibility profile for the adhesives containing crosslinking agents comparing to the neat specimens.

Photopolymerization of dental resin as restorative material using an argon laser.

The effect of the 488-nm wavelength of argon laser at different power densities and irradiation times on the degree of conversion (DC), temperature rise, water sorption, solubility, flexural strength, flexural modulus, and microhardness of bisphenole A glycol dimethacrylate and triethylen glycol dimethacrylate with a mass ratio of 75:25 was studied. Camphorquinone and N,N'-dimethyl aminoethyl methacrylate were added to the monomer as a photo initiator system. The DC% of the resin was measured using Fourier transform infrared spectroscopy. The maximum DC% (50%), which was reached in 20 s, and temperature rise because of the reaction (13.5 degrees C) were both higher at 1075 than 700 mW/cm(2). Water sorption and solubility were measured according to ISO4049, which in our case were 23.7 and 2.20 microg/mm(3) at 1075 mW/cm(2), respectively. A flexural modulus of 1.1 GPa and microhardness of 19.6 kg/mm(2) were achieved above the power density. No significant difference was observed (i.e., p>0.05) for water sorption and flexural strength at 700 and 1075 mW/cm(2).

The effect of ceramic and porous fillers on the mechanical properties of experimental dental composites.

OBJECTIVES: The purpose of this study was to investigate the effect of ceramic fillers (containing leucite crystals) and their porosity on the mechanical properties of a new experimental dental composite in order to compare with the properties of composites containing conventional glass fillers. METHODS: In this study, experimental composites were prepared by mixing the silane-treated fillers with monomers. Experimental composites were divided into four groups according to their filler type, amount and porosity. The monomers were composed of 70% Bis-GMA and 30% TEGDMA by weight for all groups. Glass and leucite-containing-ceramic were prepared as different filler types. In order to make fillers porous, leucite-containing-ceramic fillers were treated with HF acid. Camphorquinone and DMAEMA were used as photo initiator system. Post-curing was done for all groups before mechanical testing. Degree of Conversion of composites was measured using FTIR spectroscopy. The diametral tensile strength (DTS), flexural strength and flexural modulus were measured and compared among the groups. RESULTS: The results showed that the stronger and more porous filler has a positive effect on flexural strength. Porosity of filler increased flexural strength significantly. No significant difference was found in DTS tests among the groups. Flexural modulus was affected and increased by using ceramic fillers. The type of the filler affected the DC of the composite and DC increased by post-curing. SIGNIFICANCE: Flexural strength is one of the most important properties of restorative dental materials. Higher flexural strength can be achieved by stronger and more porous fillers. Investigation into the effect of filler on dental material properties would be beneficial in the development of restorative dental material.

Synthesis and characterization of novel injectable, biodegradable and in situ crosslinkable poly(hexamethylene-carbonate-fumarate), poly(hexamethylene carbonate) diacrylate and poly(ethylene glycol fumarate-co-hexamethylene carbonate-fumarate) scaffolds for bone tissue engineering.

A series of novel self-crosslinkable and biodegradable polymers; poly(hexamethylene carbonate-fumarate), poly(hexamethylene carbonate) diacrylate and their amphiphilic copolymers with polyethylene glycol, poly(ethylene glycol fumarate-co-hexamethylene carbonate-fumarate) (PEGF-co-PHMCF) were developed for tissue engineering using novel synthesis approach. These novel polymers were fully characterized using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, rheometry and shrinkage strain measurement. The cytocompatibility of macromers and their networks were evaluated by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] MTT assay. The synthetic macromers were light colored with self-crosslinking ability via both photocrosslinking and chemical crosslinking. These polymers can be used as precursors to prepare polymer networks and scaffolds with controlled hydrophilicity, biodegradability and mechanical characteristics for application in cell delivery, tissue engineering and controlled release of biologically active agents.

Physical and mechanical properties of an experimental dental composite based on a new monomer.

OBJECTIVE: The purpose of this study was to investigate the physical and mechanical properties of a dental composite based on BTDMA, a new dimethacrylate monomer based on BTDA (3,3',4,4'-benzophenone tetracarboxylic dianhydride), and to compare these with the properties of a composite based on commonly used Bis-GMA monomer. METHODS: Experimental composites were prepared by mixing the silane-treated filler with the monomers. The prepared pastes were inserted into the test molds and heat-cured. Light-cured composites were also prepared using camphorquinone and amine as photoinitiator system. Degree of conversion of the light-cured and heat-cured composites was measured using FTIR spectroscopy. The flexural strength, flexural modulus, diametral tensile strength (DTS), water sorption, water contact angle, microhardness and thermal expansion coefficient of the prepared composites were measured and compared. Water uptake of the monomers was also measured. RESULTS: The results showed that the mechanical properties of the new composite are comparable with the properties of the Bis-GMA-based composite but its water sorption is higher. BTDMA as a monomer containing aromatic rings and carboxylic acid groups in its structure gives a composite with good mechanical properties. There is a close relation between the contact angle, water sorption of the cured composite and water uptake of their monomers. SIGNIFICANCE: Finding new monomers as alternatives for Bis-GMA have been a challenge in the field of dental materials and any investigation into the properties of new composites would be beneficial in the development of dental materials.

Aneurysm of the mitral valve in a patient with hypertrophic cardiomyopathy.

We report a case of mitral valve aneurysm and severe mitral regurgitation complicating infective endocarditis in a patient with hypertrophic cardiomyopathy. 2-dimensional echocardiography revealed a saccular structure in the anterior mitral leaflet that bulged into the left atrium throughout the cardiac cycle. Pathology of the excised valve showed inflammation, early repair and perforation of the aneurysm. Concurrent mitral insufficiency or trauma resulting from septal-anterior mitral leaflet contact may predispose to valvular infection. The repair process of this damaged focus and the loss of the elastic properties of the valve may contribute to aneurysm formation. The aneurysm in this case formed in less than 5 weeks.

Persistent left superior vena cava draining into the left atrium, atrial septal defect, and absence of the coronary sinus. Recognition and surgical correction.

The diagnosis of atrial septal defect (ASD), persistent left superior vena cava (LSVC) and absence of coronary sinus was established by cardiac catheterization in a 20 years old female. At surgery the coronary vein ostia were located in the left atrium. LSVC was ligated and pericardial patch was sutured around the orifices of the coronary veins and extended to the ASD to redirect the coronary blood flow into the right atrium and close the defect. The postoperative cardiac catheterization and hemodynamic studies revealed good result.

Enlargement of mitral valvular ring. New technique for double valve replacement in children or adults with small mitral anulus.

The technical difficulty of inserting a sufficiently large prosthesis in a small mitral ring has been overcome by a new technique based on the principle of complete division of the valvular ring and its unrestricted enlargment by reconstruction of the prosthetic valve. Th technique entails division of the aortic valvular ring into and through the mitral anulus and the left atrial wall. It provides wide exposure for easy double mitral and aortic valve replacement, which is performed with large prosthetic valves that are supported in part by the patch reconstruction of the incised structures. This method has been used with excellent technical and good early functional results in two children needing double valve replacement for rheumatic mitral and aortic regurgitation. A wider adoption of this technique to manage similar lesions in both children and adults seems advisable.

[Surgical procedure in exploratory incision of the mamma (author's transl)]. / Operatives Vorgehen bei der Probeexzision aus der Mamma.

A comparison was made between two groups, each consisting of 50 women who had undergone an exploratory incision of the mamma because of suspected cancer at least one year and not more than two years previously. The women in group A underwent an operation in clinic A in which a radial incision was performed in the skin immediately above the tumor (GB: tumour). In contrast to this group B in clinic B had the tumor removed via parariola incision independent of the location of the tumor. In clinic A the incision was closed by subcuticular suture using individual button stitches on the surface. In clinic B subcutaneous stitching was not used; after thorough blood-staunching procedures the skin was closed with intracutaneous atraumatic techniques. Both groups were subsequently examined and post-operative complications and the complaints of the patients were registered. In addition the cosmetic result of the operation was taken into consideration. The examinations show that the parariola incision is the ideal technique for almost all exploratory operations of the breast. Although the post-operative phase is accompanied by a slightly higher incidence of haematomas these rarely require further corrective surgical procedures if blood-staunching is efficient and Redon drainage techniques are used. Between 1 and 2 years after surgery the parariola approach shows definite advantages when compared with radial incision directly over the tumor. The scars are almost invisible, definitely cause fewer problems for the patient, and rarely spoil the appearance of the breast.