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An intraoral acrylic mold technique to guide and maintain beam direction during oral roentgen therapy is described. It is used in combination with the treatment cone and a lead tube and protective diaphragm for collimation of the beam.
Shaped filters that are constructed of lead-loaded acrylic material for use in patient radiography are discussed. Use of the filters will result in improved overall image quality with significant exposure reduction to the patient (approximately a 2X reduction in breast exposure and a 3X reduction in thyroid gland exposure). Detailed drawings of the shaped filters for scoliosis radiography, cervical spine radiography, and for long film changers in special procedures are provided. The use of the scoliosis filters is detailed and includes phantom and patient radiographs and dose reduction information.
Percutaneous osteoplasty with acrylic bone cement was performed in 12 acetabular osteolytic lesions in 11 patients with inoperable metastases (n = 8) and myeloma (n = 3). Complementary radiation therapy was started 15-30 days after injection in each case. Pain diminished within hours to 4 days in nine patients, and walking improved in each patient within 1-5 days. Five patients died during the follow-up period. Clinical improvement was maintained in all but two patients.
The advantages of using antibiotic acrylic resin in the reconstruction of the orbit following injury or tumor removal are described. Four cases are presented whose long-term results confirm the value of the new method.
Cytocompatible polyurethane (PU) surface was prepared by photo-grafting 2-hydroxyethyl acrylate (HEA) onto the membrane surface. Graft polymerization was conducted by combining the use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane, immersed previously in monomer solution, was irradiated under UV light. The ATR-FTIR spectra, element spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle characterized the grafted copolymers and verified the occurrence of graft polymerization. The results showed that UV irradiation could realize the graft polymerization effectively and the grafting was confined within the surface layer. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelial (HUVE) cells were seeded on the grafted surface. The performance of the surface in cell attachment and growth correlated with the oxygen content and mainly the carbonyl content on the surface. Cells were spread more extensively and grew faster on the surface with a higher oxygen content.
The specific interactions of local anesthetic lidocaine hydrochloride with poly(acrylic acid) and poly(2-hydroxyethyl vinyl ether), as well as in a triple system composed of the drug and both polymers, have been studied in aqueous solutions by viscometric, turbidimetric, potentiometric, and FTIR spectroscopic methods. The mechanism of the drug binding to the polymers and the structures of the polycomplexes formed are clarified.
In order to improve the cytocompatibility of polyurethane (PU) porous scaffolds obtained by thermally-induced phase separation, poly(hydroxylethyl acrylate) (PHEA) was covalently immobilized by grafting copolymerization of HEA by photo-oxidation of the scaffolds and initiation of UV light. FT-IR-ATR spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations confirmed the occurrence of the grafting co-polymerization of HEA on the porous PU scaffolds. The measurement of water absorption demonstrated the improvement of the hydrophilicity after grafting with PHEA. The results obtained in a human umbilical vein endothelial cell (HUVEC) culture proved that the porous PU scaffold modified with the hydrophilic PHEA had better cytocompatibility than the control. The influence of surface pore size on the HUVEC growth behavior was assessed regarding cell anchorage, proliferation and viability, as well as morphology. An overall increase of cell number and viability with the decrease of the surface pore size was found.
Poly(propyl acrylic acid) (PPAA) is a polymer specifically designed to disrupt lipid bilayer membranes within a sharply defined pH range. The pH sensitivity can be used to enhance the release of endocytosed drugs into the cytoplasmic compartment of the cell. By incorporating this polymer in a polymeric gene carrier, chitosan, the release of plasmid DNA from the endosomal compartment was enhanced. In vitro transfection studies confirmed that the incorporation of PPAA into the chitosan-DNA nanoparticles enhanced gene expression in both HEK293 and HeLa cells compared to chitosan nanoparticles alone. The dose and time at which PPAA was incorporated during the complex formation affected the release of DNA and transfection efficiency. The optimal dose of PPAA incorporated into the chitosan nanoparticles was determined to be 10 microg, corresponding to a PPAA/DNA weight ratio of 1:1. At this dose, the ternary complexes are approx. 400 nm in size with a net negative surface charge of -17.4 mV. Intracellular trafficking studies confirmed the association of PPAA, DNA and chitosan at 24 h post-transfection and the subsequent release of DNA and PPAA from the chitosan at 48 h. The diffuse appearance of the majority of the DNA and the PPAA at later time points suggests that the PPAA triggered membrane disruption resulting in the release of DNA from the endosomal compartment. Finally, the lack of colocalization between PPAA and Lysotracker indicated that the PPAA-loaded nanoparticles were not trafficked through a lysosomal pathway. This study suggests the promising strategy of including PPAA in the formulation of polymer-DNA complexes for non-viral gene delivery.
Poly(acrylamide-co-acrylic acid) (poly(AM-co-AA)) superporous hydrogels (SPHs) were synthesized and the acidification effects on the swelling and mechanical properties were studied. Gelation exotherms were measured to determine the optimum introduction time for adding a blowing agent. The gelation kinetics decreased with increasing the AA concentration. The maximum equilibrium swelling was observed around an AA weight fraction of 0.4, but the compressive strength decreased monotonically with increasing the AA concentration. Poly(AM-co-AA) SPHs were much less swollen in acidic solution than in distilled water of pH 6.7. The swelling ratio decreased with increasing acidity (decreasing pH). Reduction of water absorption content by acidification led to considerable increase in the mechanical strength.
Films of polytetrafluoroethylene (PTFE) were modified by radiation graft polymerization of acrylic acid (AAc). Optimal conditions for efficient AAc grafting were studied, including pre-irradiation dose in air, monomer concentration, temperature and time of the grafting process. Carboxylic groups of the grafted polyAAc were activated with carbodiimide (EDC) for biotinylation by reaction with 5-(biotinamido) pentylamine. Streptavidin-horseradish peroxidase (SA-HRP) was immobilized by affinity complexation of the SA with the biotin groups on the PTFE surface. The amount of active HRP immobilized on the PTFE films was determined as a function of the extent of polyAAc grafting. This study has demonstrated the utility of combining the processes of (a) radiation grafting of polymers with reactive groups onto inert polymers such as PTFE, (b) biotinylation of the graft polymer reactive groups, (c) immobilization of streptavidin on the biotinylated surface sites, followed by (d) immobilization of biotinylated, biologically active molecules via complexation of their conjugates with streptavidin. In this study, the last two steps were combined by immobilizing the complex of streptavidin and biotinylated HRP onto the biotinylated surface sites. The unique nature of this process is the ability to immobilize biotinylated molecules on an inert surface as PTFE.
Alginate microcapsules enclosing recombinant cells secreting therapeutic products have been used successfully to treat several murine models of human diseases. The mechanical and chemical properties of these alginate capsules can be improved by the addition and in situ photo-polymerization of sodium acrylate and N-vinylpyrrolidone in the alginate capsule. The purpose of this modification was to form additional covalent cross-links. In this work we have used scanning transmission X-ray microscopy (STXM) to probe the nature and location of the chemical modifications in the modified capsules by comparison with unmodified capsules. Analysis of X-ray image sequences and selected area spectra has been used to map the calcium gradient in capsules, to identify the presence of polyacrylate throughout the capsules and the localization of poly-N-vinylpyrrolidone in the outer regions of the alginate capsules. The differences in the spatial distributions of these species have led to better understanding of the chemical modifications that provide a mechanically more stable capsule structure.
Pneumoconiosis in dental laboratory workers has been associated with exposure to metal alloys and silica used in the manufacturing of dental prosthetics. In this report, we describe a 27-yr-old dental student who was found to have bilateral basal pulmonary interstitial infiltrates and nodules on a chest roentgenogram after a brief episode of upper respiratory infection. An open lung biopsy revealed interstitial pneumonitis with an abundance of vacuolated macrophages in the alveolar spaces. Ultrastructural analysis showed in the alveolar and interstitial spaces the accumulation of macrophages laden with electron-lucent bodies resembling plastic beads. An inhalation exposure history, taken subsequent to these findings, revealed exposure to high levels of acrylic plastic in a dental school laboratory. Removal from the site of exposure has resulted in the gradual resolution of the roentgenographic abnormalities.
Organically modified silica (ormosil) particles were prepared using hydrolytic sol-gel methods and the miniemulsion polymerisation approach. Methyl-, ethyl-, and phenylsilsesquioxane nanoparticles with diameters in the range 50-180 nm were obtained using the modified Stöber method with an aqueous sodium silicate solution used as a seed for further growth of the particles. Methyl- and phenylsilsesquioxane particles were prepared by a sol-gel method in the presence of benzethonium chloride used as a surfactant. The miniemulsion polymerisation approach has been extended to the production of methacrylate-modified silica nanoparticles with vinylpyridine or lauryl methacrylate used as comonomers both in the presence and in the absence of a surfactant. Styryl-modified silica particles with diameters in the range 300-800 nm were obtained by the Stöber method using pre-formed SiO2 nanoparticles as the seeds for silsesquioxane nanoparticle formation. The effect of incorporation of the particles produced using different synthetic methods on hardness and water resistance of acrylic coating systems was studied here.
The adhesion of acrylic composite restorative materials to etched dental enamel is increased by a factor of two or more when the enamel is coated with a thin layer of vinyl-benzyl phosponic acid (VBPA) prior to forming the enamel-restorative bond. The present results support the suggestion that the enhanced adhesion is attributable to bonding between calcium ions in the enamel surface and phosphonate groups in the VBPA.
Strength and durability of the dentin-acrylic resin joint cemented with 2-cyanoacrylate esters were studied. Maximum adhesion is obtained with isobutyl 2-cyanoacrylate after 1% acid pretreatment of the dentin. Hydrolytic stability is somewhat improved by addition of polymer to the adhesive or coating around the joint.
Male F344/N rats were dosed with ethyl acrylate (EA) either by daily gavage or in the drinking water for 2 weeks. The gavage dose levels were 0, 2, 10, 20, 50, 100, and 200 mg/kg; the drinking water dose concentrations were 0, 200, 1,000, 2,000, and 4,000 ppm (corresponding to 0, 23, 99, 197, and 369 mg/kg/day, respectively). In those animals dosed by gavage, irritation of the forestomach increased in incidence and severity over the 20-200 mg/kg dose range. In those animals dosed with EA in the drinking water, a much lower incidence of forestomach irritation and less severe lesions were observed at corresponding dose levels. No lesions were observed in the glandular stomach from either of the 2 modes of oral administration. Following 2 weeks of gavage dosing with EA, the total non-protein sulfhydryl (NPSH) content of the forestomach and glandular stomach, and the NPSH concentration of the liver were determined 2-24 hr after the last gavage dose. Animals dosed at 200 mg/kg reached approximately 11% of the initial NPSH content in the forestomach at 6 hr after dosing. NPSH depletion of this magnitude has been associated with cytotoxicity of other tissues in other studies. By contrast, either the glandular stomach nor liver were depleted of NPSH to levels generally associated with toxicity. These observations are consistent with the conclusion that bolus dosing of EA induces severe depletion of critical cellular thiols in the forestomach with toxic consequences, but not in the glandular stomach or liver. Changing the mode of oral administration for EA to continued small doses in the drinking water allowed efficient detoxification and did not induce sulfhydryl depletion or comparable forestomach toxicity at the same daily body burden.
Ethyl acrylate (EA) is a known forestomach carcinogen in both rats and mice. Recent work in this laboratory indicated that carcinogenic doses of EA administered by gavage for 13 wk resulted in a sustained increase in forestomach epithelial hyperplasia as long as exposure to EA continued. However, hyperplasia regressed and no forestomach neoplasms were seen after a 19-mo recovery period. Current studies were designed to further investigate the time required for sustained hyperplasia to lead to neoplasia as well as the organ specificity of EA-induced cell proliferation/hyperplasia vs carcinogenicity. EA was administered at 200 mg/kg (po) to male Fischer-344 rats, 5 days/wk. Squamous cell proliferation/hyperplasia was observed in the forestomach of all rats that received EA for 6 or 12 mo. Treatment of rats with EA for 12 mo followed by 2 mo of recovery resulted in the development of forestomach papillomas in 2 of 5 treated rats. Furthermore, animals treated for 12 mo and allowed 9 mo of recovery exhibited an increase in forestomach squamous cell carcinomas and papillomas at a combined incidence of 4 in 13. In contrast, animals treated with EA for 6 mo and allowed 2 or 15 mo of recovery exhibited a time-dependent regression of cell proliferation and did not develop forestomach neoplasms. No significant elevation in liver cell proliferation or neoplasia was seen at any time in any of the rats included in the present study, further confirming the organ specificity in the relationship between EA-induced cell proliferation and carcinogenicity. In conclusion, EA resulted in increased cell proliferation in the target organ of carcinogenicity (forestomach) but not in nontarget organs such as the liver. This work indicates that cell proliferation, sustained for a sufficient period of time, results in the development of neoplasia despite cessation of chemical administration. Furthermore, a temporal relationship exists between EA-induced epithelial cell proliferation and forestomach carcinogenicity.
There are numerous examples in dentistry where demineralization, or even frank caries, develops near or in association with restorative or prosthetic materials. Leaking cavity margins and demineralization under bite splints are two examples. A slow-release source of fluoride could help to prevent these problems and provide added protection throughout the mouth. For this purpose a family of fluoride-releasing resins has been developed for use in various adhesive applications, and also for preparing temporary crowns and removable acrylic devices. These materials contain fluoride ions held to covalently bound positive charge sites within the polymer network. Release is by a diffusion/exchange mechanism in which anions from oral fluids diffuse to the charge sites and exchange with fluoride. Fluoride then diffuses to the surface and is released into solution. This method of release allows for the retention of adequate physical properties and is capable of a linear release rate for terms ranging from days to years.