Pharmacokinetics and toxicity of 120-hour continuous-infusion hydroxyurea in patients with advanced solid tumors

This study investigated the thickness of a swollen layer between heat-activated and autopolymerized denture base polymer based on poly(methyl methacrylate) and autopolymerized repair acrylic resin. The repair surfaces of polymerized poly(methyl methacrylate) resin specimens (n = 5) were wet with methyl methacrylate liquid for 0, 0.5, 3, 30, or 60 minutes before the mixed repair resin was applied and polymerized to the surface of the specimen. The specimens were wet ground to a thickness of 0.15 mm, and the repair joint was examined using a light microscope. The thickness of the layer of swollen poly(methyl methacrylate) at the repair joint was measured from the micrographs. Both the type of polymer, ie, heat-activated or autopolymerized, and the wetting time of the repair surface with methyl methacrylate had a significant effect on the thickness of the swollen layer (P < .001). Prolonged wetting time of the repair surface of the autopolymerized poly(methyl methacrylate) increased the thickness of the swollen layer (r = .944, P = .000), but had less effect on the thickness of the swollen layer of heat-activated poly(methyl methacrylate) (r = .391, P = .005). This study suggests that methyl methacrylate diffuses more easily into an autopolymerized poly(methyl methacrylate) than into heat-activated poly(methyl methacrylate) during the repair of denture base polymer.     

Reinforcement of acrylic resins for provisional fixed restorations. Part I: Mechanical properties

Acrylic resins are commonly used in many dental applications; especially in the fabrication of provisional fixed partial dentures. Among noticed technical drawbacks associated with this material are unsatisfactory mechanical properties. Moreover, if acrylic resins are exposed to moist environment, water sorption results in further mechanical deterioration. In order to improve the mechanical properties, aluminum, magnesium, and zirconium oxide powders and pulverized E-glass particles were separately admixed with pre-polymerized acrylic resin beads prior to mixing with monomer liquid. Particle loading ratios were 1, 2 and 3 vol.% with respect to pre-polymerized beads. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(isobutyl methacrylate) were used as resin matrices. Furthermore, a metal primer agent was employed in order to form a strong interphase between admixed particles and polymer matrix phase. Samples were subjected to three-point transverse bending tests at a crosshead speed of 10 mm/min. It was concluded that (1) addition of particles generally increases the water sorbed by the composite resins systems, (2) however, two vol.% admixtures in a PMMA resin matrix showed significant improvements in the mechanical properties (p < 0.05), (3) among the oxide particles, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness and hardness, and (4) mechanical properties (transverse strength, 0.2% offset yield strength and modulus of elasticity) were linearly correlated to hardness numbers.     

Effect of polymerization temperature and time on the residual monomer content of denture base polymers

The aim of this study was to investigate the effect of polymerization time and polymerization temperature on the residual methyl methacrylate (MMA) content of two heat-cured and two autopolymerized denture base polymers. Gas chromatography was used to determine the residual MMA content of three test specimens of each type of polymer. Increasing the polymerization temperature for the autopolymerized denture base resins from 30 degrees C to 60 degrees C decreased the residual MMA content of the polymer from an average of 4.6 wt% to 3.3 wt%. With the heat-cured denture base resins, a curing cycle at a polymerization temperature of 70 degrees C followed by a period at 100 degrees C significantly reduced the residual monomer content of the polymer when compared with a resin cured at 70 degrees C only. Polymerizing the heat-cured denture base resin at 100 degrees C only for various lengths of time significantly affected the residual MMA content of the polymer. The lowest residual MMA content (0.07 wt%) was obtained by polymerizing the heat-cured denture base resin at 100 degrees C for 12 h. The results of this study suggest that the polymerization temperature and polymerization time considerably affect the residual MMA content of denture base polymers.     

Breeding of Philander frenata (Didelphimorphia, Didelphidae) in captivity

STATEMENT OF PROBLEM: Because water sorption of autopolymerizing acrylic reline resins is accompanied by volumetric change, it is a physical property of importance. As residual monomer leaches into the oral fluids and causes tissue irritation, low solubility of these resins is desired. Another requirement is a satisfactory bond between the autopolymerizing acrylic resins and the denture base acrylic resin. PURPOSE: This study compared the water sorption, solubility, and the transverse bond strength of 2 autopolymerizing acrylic resins (Duraliner II and Kooliner) and 1 heat-polymerizing acrylic resin (Lucitone 550). MATERIAL AND METHODS: The water sorption and solubility test was performed as per International Standards Organization Specification No. 1567 for denture base polymers. Bond strengths between the autopolymerizing acrylic resins and the heat-polymerizing acrylic resin were determine with a 3-point loading test made on specimens immersed in distilled water at 37 degrees C for 50 hours and for 30 days. Visual inspection determined whether failures were adhesive or cohesive. RESULTS: Duraliner II acrylic resin showed significantly lower water sorption than Kooliner and Lucitone 550 acrylic resins. No difference was noted in the solubility of all materials. Kooliner acrylic resin demonstrated significantly lower transverse bond strength to denture base acrylic resin and failed adhesively. The failures seen with Duraliner II acrylic resin were primarily cohesive in nature. CONCLUSIONS: Autopolymerizing acrylic reline resins met water sorption and solubility requirements. However, Kooliner acrylic resin demonstrated significantly lower bond strength to denture base acrylic resin.     

Fimbrial-mediated colonization of murine teeth by Actinomyces naeslundii

PURPOSE: The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat-polymerized denture base resin and two resins designed for microwave polymerization were evaluated. MATERIALS AND METHODS: Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were than embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity. RESULTS: There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 microns. CONCLUSIONS: Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.     

Peak temperatures of some prosthetic acrylates on polymerization

The aim of this study was to determine peak temperatures of some prosthetic acrylic resins at the time of polymerization. The acrylic resins included two temporary restoration resins, three autopolymerizing resins for different applications and one heat-cured denture base resin. The peak temperatures were measured with a ferro-constantan thermocouple from test specimens of three different volumes at different temperatures. The results revealed that with increasing volume of polymerizing acrylic resin the peak temperature also increased. In general, acrylic resins for temporary restorations had lower peak temperatures than other acrylic resins. However, despite the lower peak temperatures, the temperature of temporary restoration resins during polymerization can be as high as 82 degrees C. Therefore, to minimize thermal injuries of the tissues of vital tooth, dentists must be aware of the heat formation of the acrylic resins used in the oral cavity.     

Mechanical strength of acrylic bone cements impregnated with antibiotics

Admixing of several antibiotic powders which were insoluble in methyl methacrylate did not decrease the compressive and diametral tensile strengths of two acrylic bone cements when tested after setting for 1 day and after leaching 40 days in water at 37 degrees C. When antibiotics were added as water solutions, the included water resulted in a significant decrease in these bulk mechanical properties. Storage in water for 40 days caused surface irregularities only on specimens of the set antibiotic admixtures. Approximately 0.5% of the admixed dosage of these water-soluble antibiotics could be leached from the set cements. The observed surface channels, presumably left by the loss of antibiotic, suggest further study of surface-sensitive mechanical properties may be needed. The bulk mechanical strengths presented here are conclusive only for the particular combinations of antibiotics and cements investigated, and should not be generalized at this time to any or all antibiotic admixtures or other mechanical properties.     

Alternative Sorbents for Removing MTBE from Gasoline-Contaminated Ground Water

The objective of this work is to provide a preliminary screening of the effectiveness of alternative sorbents for treating ground water contaminated with methyl tert-butyl ether (MTBE). Sorbents studied include synthetic carbonaceous resins, porous graphitic carbon, C18 silicas, and acrylic resins. Activated carbon was also tested for comparison purposes. Bottle point isotherms show that porous graphitic carbon and two synthetic carbonaceous resins have a greater capacity for MTBE than activated carbon. However, the required addition of a wetting agent to suspend and activate the porous graphitic carbon makes this sorbent unsuitable for drinking water purposes. The synthetic carbonaceous resins tested were found to have capacities three to five times greater than activated carbon at an MTBE concentration of 1 mg∕L. The application of the Dubinin-Astakov isotherm to data for the synthetic carbonaceous resins suggests that the mechanism of adsorption is micropore filling. Additional bisolute experiments with m-xylene as a representative gasoline contaminant indicate that the m-xylene is preferentially sorbed, depleting the micropore volume available for MTBE sorption. The extent of this competitive adsorption was directly predicted from measured concentrations of the monoaromatic hydrocarbon.     

Monomethacrylate co-monomers for dental resins

Polymerisation shrinkage is widely recognised as a major drawback of resin based dental restoratives. Bis-GMA is often employed as the principal dimethacrylate monomer. Due to its high viscosity, Bis-GMA is normally mixed with large proportions of low viscosity glycol dimethacrylates. The purpose of this study was to determine whether the polymerisation shrinkage of Bis-GMA-based resins would be lower if alternative monomethacrylate co-monomers were used in place of conventional dimethacrylate co-monomers as viscosity modifiers. Conventional resins used were ethyleneglycol dimethacrylate and triethyleneglycol dimethacrylate; the alternative monofunctional co-monomers were tetrahydrofurfuryl methacrylate, hydroxypropyl methacrylate and isobornyl methacrylate. Model resins containing 54% mol/mol of co-monomer in Bis-GMA and 1% w/w of benzoyl peroxide as initiator were heat-cured at 70 degrees C for 8 h. Polymerisation shrinkage, degree of conversion and concentration of remaining methacrylate groups were calculated from density changes obtained gravimetrically. Other properties evaluated were Young's modulus, water uptake and viscosity of the monomer mixtures. The Bis-GMA-based resins exhibited lower shrinkage when mixed using the monomethacrylates rather than with conventional glycol dimethacrylates. Among the alternative co-monomers, tetrahydrofurfuryl methacrylate conferred the best balance of all measured properties.     

Antigen detection on resin sections and methods for improving the immunogold labeling by manipulating the resin

Considering the importance of immunolocalization of cellular substances combined with good ultrastructure and ease of use, this review is focused on the use of resin and the possibilities of manipulating the resin before and after embedding in order to improve the immunolabeling of resin sections for electron microscopy. The qualities of acrylic resins and conventional epoxy resin for immunoelectron microscopy are discussed. Acrylic sections are usually more suited for immunoelectron microscopy than conventional epoxy sections. Different etching procedures (sodium ethoxide or sodium metaperiodate) may be applied to conventional epoxy sections to enhance the yield of immunolabeling. Lately, a method which does not involve any kind of etching has been developed for enhancing the immunogold labeling of epoxy sections up to about 8 times. This method involves increased concentration of accelerator in the epoxy resin mixture when processing the tissue. The ultrastructural preservation of the tissue is important in immunoelectron microscopical procedures, and not only the intensity of the immunolabeling; in this respect no resin may compete with the widely used epoxy resins.     

Diffusion of monomers from bonding resin-resin composite combinations through dentine in vitro

OBJECTIVES: Previous work has demonstrated diffusion of the monomer triethylene glycol dimethacrylate (TEGDMA) from resin composite through dentine in vitro. The objective of the present work was to examine monomer diffusion from bonding resins and resin composites used in combination. METHODS: Occlusal cavities were prepared in tooth crowns and restored with bonding resin-resin composite combinations. Aqueous samples from the 'pulpal chamber' of each tooth were removed at timed intervals for analysis by reversed phase-high performance liquid chromatography and mass spectrometry. RESULTS: Bonding resins contributed to monomer diffusion. A TEDGMA-containing bonding resin used in combination with a TEGDMA-containing resin composite hastened and increased TEGDMA diffusion through dentine. A 2-hydroxyethyl methacrylate (HEMA)-containing bonding resin used in combination with a TEGDMA-containing resin composite reduced TEGDMA diffusion only slightly compared with the resin composite alone and added substantial diffusion of HEMA. CONCLUSION: The bonding resins tested contributed to monomer passage to the pulp space and did not prevent movement of monomer from resin composites to the pulp.     

Memory training for remembering names: initial results in the healthy elderly

It has been known since the 1940s that nail polishes contain allergenic ingredients. The aim of this study was to clarify whether the nail polishes on the market today contain significant amounts of allergens, and what the solvents are. The following ingredients were determined: toluene, toluene sulfonamide formaldehyde resins, free formaldehyde, acrylates, methacrylates and certain organic solvents. The study comprised 20 brands and 42 samples. All the nail polishes analysed contained allergenic toluene sulfonamide formaldehyde resins (TSFR), in concentrations from 0.08 to 11.0%. The concentration of total formaldehyde varied from 0.02% to 0.5%. The more TSFR a nail polish contained, the higher was its formaldehyde content. Probably not only TSFR-allergic but also formaldehyde-allergic persons may get dermatitis from many of the nail polishes studied. The concentrations of acrylates and methacrylates were so small that they are of practical significance only to those previously sensitized to acrylates. Of the organic solvents, toluene was still widely used, whereas xylene was found in only 1 product. The nail polishes on the market today are not safe for all consumers. However, according to the regulations of the European Union, the packaging labeling of all cosmetic products must be supplied with a list of ingredients from the beginning of 1998. This will help the consumer to avoid allergenic products. A better alternative could, however, be to substitute the most allergenic ingredients with substances possessing minor allergy potency.     

The evaluation of acrylic resins for the study of nondecalcified human teeth with the light and electronic microscopes

Resin embedding of human teeth for light and transmission electron microscopic studies becomes difficult without previous decalcification. The limited and slow infiltration of the resin into hard tissues may cause problems during preparation and observation of the samples. Moreover the type of resin that is used may affect the morphologic preservation of both tissues and cellular elements. Recently there has been an increasing number of studies on the application of acrylic resins in light and electron microscopy, in order to overcome problems encountered with the use of epoxy resins still utilized in morphologic studies. We compared different acrylic resins (Technovit 7200 VLC, LR White, LR Gold, Bioacryl) in order to understand which one was more suitable for undecalcified human dental tissues under light and transmission electron microscope. Evaluation of such resins was performed using the following criteria: ease of cutting with ultramicrotome, soft and hard tissues infiltration, uptake of tissue stains for both light and electron microscopy, morphologic preservation and stability under electron beam. This study, carried out on the pulp area comprising predentin and dentin, showed excellent quality of Bioacryl and LR Gold, the two resins presenting, by far, the best results among all the different types tested. The optimal morphologic preservation obtained with such resins is indicated for light and electron microscopic studies, allowing their application in different fields of dental research.     

Iodinated methacrylate copolymers as X-ray opaque denture base acrylics

OBJECTIVES: The purpose of this study was to evaluate novel iodinated methacrylate copolymers as X-ray opaque denture base resins. METHODS: The synthesis of specific monomers and suspension copolymerization with methyl methacrylate to produce copolymer beads. The resulting beads were processed in an identical manner to standard PMMA to produce test-pieces for mechanical testing. RESULTS: Samples prepared from beads containing 25 wt% of the iodinated copolymer exhibited an X-ray opacity equivalent to that exhibited by a similar thickness of aluminium. Furthermore, the appearance and mechanical properties were comparable to standard PMMA, while thermal stability proved superior. CONCLUSION: These novel iodinated methacrylate monomers show promise not only as polymerizable additives to methyl methacrylate to produce an X-ray opaque denture base but also as thermally stable copolymerizable additives to other applications where X-ray opacity would be advantageous.     

Mitogenic effect of retinoid X receptor agonists in rat liver

Thirty-nine acrylates and methacrylates that had been used in dental resin materials were evaluated by a cytotoxicity test, and the relationships between their structures and cytotoxicity were studied to predict cytotoxic levels of dental resin materials in order to develop new low-toxic resin materials. All the acrylates evaluated were more toxic than corresponding methacrylates. In both the acrylates and methacrylates, a hydroxyl group seemed to enhance cytotoxicity. Dimethacrylates with 14 or fewer oxyethylene chains showed similar cytotoxicity while dimethacrylates with 23 oxyethylene chains showed lower cytotoxicity. The cytotoxicity ranking of monomers widely used in dental resin materials was bisphenol A bis 2-hydroxypropyl methacrylate (bisGMA) > urethane dimethacrylate (UDMA) > triethyleneglycol dimethacrylate (3G) > 2-hydroxyethyl methacrylate (HEMA) > methyl methacrylate (MMA). In acrylates, methacrylates, and ethylmethacrylates with either substituents, the lipophilicity of substituents affected their cytotoxicity, and an inverse correlation between IC50 and logP was observed. These results will be useful in developing new resin materials with low toxic monomer compositions.     

-Coexistence of neural proliferations with early epithelial neoplasias and benign ectopias of the uterine cervix-

A method for processing and embedding alginate-polylysine microencapsulated pancreatic tissue in glycol methacrylate resin (GMA) is described. Fixation in 4% phosphate buffered formaldehyde, processing in ascending concentrations of glycol methacrylate monomer and embedding in Technovit 7100 results in well preserved morphological details of hydrogels, hydrogel-cell interfaces, and encapsulated pancreatic tissue. Routine staining with Loeffler's methylene blue, hematoxylin and eosin, and Romanovsky-Giemsa gave excellent images of the GMA embedded alginate polylysine membrane and tissues allowing cells on the outside of the capsule to be analyzed effectively as part of the foreign body reaction against the capsule membrane.     

A new method of acrylic cranioplasty

BACKGROUND: Previous acrylic cranioplasty techniques have relied on wire or suture fixation of the acrylic to the skull. A new methyl methacrylate cranioplasty technique, using acrylic with titanium plating, is described. METHODS: Titanium plates were bent into a "Z" shape and attached to the skull at the perimeter of the skull defect, extending into the defect. The acrylic was then poured into the defect and held in place during setting with a sheet of plastic. The plates are thereby embedded in the acrylic. RESULTS: Standard methyl methacrylate and titanium plates and screws were used to perform a new method of cranioplasty. CONCLUSIONS: A rigid, form-fitting, aesthetic construct can be easily and quickly created. This technique also offers the benefit of allowing secondary craniotomy, if necessary.     

石煤浸出液离子交换法提钒的研究

选择了几种离子交换树脂,对石煤酸浸含钒液在不同条件下进行离子交换实验.结果表明:采用离子交换法能够很好地除去浸出液中大部分杂质,并能使钒得到富集;不同树脂对钒的吸附均受吸附时间、溶液pH值等实验条件的影响,不同解吸剂与解吸时间也会影响树脂解吸的效果;1#树脂吸附率在4h左右可达到99%的最大吸附能力,选择合适的解吸剂可在4h内使钒的解吸率达到95%以上;解吸液经过净化,沉钒,煅烧后得到的五氧化二钒纯度在99%以上.     

Contribution of emotionally traumatic events and inheritance to the report of current physical health problems in 4042 Vietnam era veteran twin pairs

STATEMENT OF PROBLEM: Use of temporary crowns and fixed partial dentures is especially relevant when the treatment plan requires restorations for long interim periods, and the in-service discoloration of provisional restorative materials is a major drawback. PURPOSE: This study evaluated the discoloration effect of coffee and tea on some materials that are commonly used in the fabrication of provisional restorations. MATERIAL AND METHODS: Six commercially available provisional resins (Jet, Caulk TBR, Protemp Garant, Luxatemp Solar, Provipont DC and SR-Ivocron-PE) were evaluated after 1 day, 7 days, and 30 days of immersion in various staining solutions. Color measurements were obtained by using a Dr Lange Micro Color tristimulus colorimeter and color differences (delta E*) were estimated. RESULTS: The 2 chemically activated resins (Jet and Caulk TBR) and the heat-cured resin (SR-Ivocron PE) exhibited the least color changes, whereas the Provipont-DC resin was the least color stable. After immersion for 30 days, the combination with the coffee solution resulted in unacceptable discoloration for all the tested materials. CONCLUSIONS: Provisional restorative materials, staining solutions, and immersion time were significant factors that affected color stability. After immersion for 7 days, all materials showed observable color changes. The composite-based materials, especially light-curing composites, were the least color stable. The coffee solution exhibited more staining capacity than the tea solution.     

Reinforcement of acrylic resins for provisional fixed restorations. Part II: Changes in mechanical properties as a function of time and physical properties

In Part I, it was found that (i) 2 vol.% admixture of reinforcing elements in PMMA (Jet) resin matrix had a significant beneficial effects on the mechanical properties, and (ii) among these, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness, and hardness number. Using the best combination (i.e., PMMA resin matrix and 2 vol.% ZrO2), exothermic temperature raise and polymerization shrinkage were further investigated. Deterioration in mechanical properties due to prolonged water sorption were also studied for 5 weeks. The following can be concluded: (1) By increasing liquid/powder ratio for PMMA control samples, the peak temperature occurrence was retarded by 3 min and raised by 8 degrees C. (2) The effect of admixed oxide particles to PMMA resin matrix or the heat generated during polymerization was not significant. (3) The polymerization volumetric shrinkage was influenced by the a mixture of particles, with increases as large as 0.9% (or 0.3% in linear shrinkage). (4) PMMA resin admixed with 2 vol.% of zirconia particles showed a continuous weight gain due to water sorption, mechanical properties appears to be increasing up to 1-week sorption, followed by rapid drop of all properties. (5) Autopolymerizing acrylic resins are a resin-resin composite material of pre-polymerized beads embedded in a newly formed acrylic matrix. The main fracture modality appears to occur through the matrix and at the interface, although some trans-beads fractures were identified. (6) It was suggested that incorporating certain type of oxide particles into the pre-polymerized beads would provide stronger resin matrix.