bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally induced stresses and rapid temperature changes in teeth
Authors: Barker Robert E. , Rafoth Robert F. , Ward Robert W. 
Published: December 2004

AbstractThe central theme of this paper revolves about an attempt to provide information and ideas that might be useful to persons interested in cryogenic dental procedures. However, a broad spectrum of thermal properties is also considered. For convenience a summary table is given for pertinent thermal and mechanical properties of dental materials. A point demonstrated is that observations which are of direct empirical utility to dentists often can be enhanced in value if viewed in terms of simple analytical models. For example, a tooth can be expected to be somewhere between a sphere and a long rod in its cooling or heating characteristics. The importance of the thermal diffusivity rather than thermal conductivity in transient phenomena is discussed. Some graphical techniques that circumvent mathematical difficulties are developed in detail. An isolated extracted tooth in contact with a coolant approaches to within 98% of its final temperature in less than 1 min but in the jaw, in contact with a cold (or hot) probe, the equilibration will take much longer. Thermally generated stresses, either due to differences in expansivities of the dentin and enamel or to large temperature gradients across a single component, can be quite large (comparable to the reported tensile strength, 9.3 MN/m2 for enamel) at cryogenic temperatures. Our observations and analysis make us believe that the reported strength of 9.3 MN/m2 is too low by at least an order of magnitude.
Lipid absorption by silicone heart valve poppets—in‐vivo and in‐vitro results
Authors: Carmen Raleigh , Mutha S. C. 
Published: December 2004

AbstractSilicone rubber poppets, apparently without exception, will absorb lipid from the blood stream. In most cases, absorption is quite low and confined to simple lipids like cholesterol and cholesterol esters. A small percentage, however, absorb an unknown material in quantities sufficient to render them variant. This material appears to be an oxidation product of polyunsaturated fatty acids formed after their absorption into the poppet by the action of molecular oxygen. In vitro experiments supporting the in vivo findings are described.
Kinetics of bone growth into cylindrical channels in aluminum oxide and titanium
Authors: Predecki Paul , Stephan J. E. , Auslaender B. A. , Mooney Vert. L. , Kirkland K. 
Published: December 2004

AbstractSamples of dense aluminum oxide, dense, porous, and surface‐oxidized titanium of varying surface roughness and containing long cylindrical channels 95–1000 μ in diameter were implanted in vivo in do femurs for periods of 2–8 weeks. The depth of ingrowth of calcified tissue into these channels was determined as a function of time, principally by electron microprobe.The most rapid bone ingrowth was obtained with 500–, 525–, and 1000–μ diameter channels in all the titanium and aluminum oxide samples. However, the fraction of any given channel cross‐section filled with bone was observed to decrease as the channel diameter increased. In these channels, ingrowth depths of more than 2000 μ were often achieved in 4 weeks after which the rate of ingrowth levelled off somewhat. A certain degree of surface rougheness (greater than 20 μ in. a.a.) appeared to be necessary for fixation and ingrowth. Ingrowth of bone into the 95‐μ diameter channels was neglibile even after 18 weeks. The presence of interconnecting fine porosity per se, was found not essential for bone ingrowth nor does it have a major effect on ingrowth kinetics.
Biocompatibility of ceramic implants in soft tissue
Authors: Davis S. D. , Gibbons D. F. , Martin R. L. , Levitt S. R. , Smith J. , Harrington R. V. 
Published: December 2004

AbstractThe degradation and biocompatibility of seveal commercially available glasses, glass‐ceramics, and ceramics have been evaluated in soft tissue. Tissue compatibility was investigated by histological and toxicological determinations. Materials degration was evaluated by weight loss and surface replica electron microscopic techniques. High lead and arsenic‐selenium‐sulfur glasses are found to be unsuitable materials for implantation due to high corrosion and toxicity. Certain borosilicate glasses are also found unacceptable because of severe corrosion. Fused quartz, aluminosilicates, certain borosilicates, alkali resistant glass, soda‐lime glass, titania frit, arsenic trisulfide, lithium and magnesium aluminosilicate, glass‐ceramics, and calcium‐fluorapatite all appear to be well tolerated and seem acceptable for soft tissue implantation on the basis of the present data. Because of the lack of sensitivity of weight change as a parameter to measure low corrosion rates, we have no data on which to estimate the actual corrosion rate. The detailed changes in surface structurte produced during the corrosion process only provide information about the corrosion mechanism and may not be correlated with the corrosion rate. A more sensitive method to study low corrosion rates in glasses may be to use radioactive tracer techniques to measure the loss in radioactivity of glasses when implanted in the peritoneal cavity rather than subcutaneously.
Hard mathacrylic polymers. III. Copolymers of ethylene or trioxyethylene dimethacrylate with 2,2‐di(4‐methacryloxyphenyl)‐propane
Authors: Atusuta Mitsuru , Nakabayashi Nobuo , Masuhara Eiichi 
Published: December 2004

AbstractCopolymers of 2,2‐di(4‐methacryloxyphenyl) propane and several glycol dimethacrylates were studied to develop a suitable polymer for crown and bridge restorations and artifical bone. The physical properties of copolymers—hardness, abrasion resistance, compressive strength, and water sorption—were measured. These properties were markedly improved by introduction of highly crosslinked structure.
Antithrombogenic characteristics of cathodically polarized copper prostheses
Authors: Gileadi E. , Stanczewski B. , Parmeggiani A. , Lucas T. , Ranganathan M. , Srinivasan S. , Sawyer P. N. 
Published: December 2004

AbstractIn previous studies from our laboratories, it was shown that metals and alloys which register negative potentials in blood vs. the normal hydrogen electrode (NHE) tend to be antithrombogenic, while those with positive potentials are invariably thrombogenic. Of the metals, only the corrodible ones fall in the first group and the noble ones in the second. Blood compatible metals appear to be essential for some types of medical devices. This paper deals with a novel approach of maintaining an implanted metallic prostheses at a negative potential. A copper vascular prostheses in a dog was made the cathode in a polarizing circuit, which in addition consists of a smal mercury battery, a resistor and an auxiliary electrode. Such experiments were conducted in three animals, and the potentials ranged from −60 to −160 mV/NHE. The three dogs were sacrificed after 6, 8, and 14 days and the tubes were examined. All tubes were free of thrombus deposits; minimal junctional thrombi were found. Two copper tubes with no polarizing circuit and registering positive potentials were occluded after 8 and 14 days, respectively. Histologic and electron‐microscopic studies of the thrombus deposits in tubes at spontaneous potentials and of the junctional thrombus deposits in the tube at negative potentials showed similar structures. The present experiments further confirm the view that the potential across the conductive material‐blood interface is a more basic parameter than the chemical nature of the surface in determining its blood‐compatible characteristic.
Effect of surface materials on shear‐induced hemolysis
Authors: Lampert Richard H. , Williams Michael C. 
Published: December 2004

AbstractA rotating shearing device with interchangeable discs of various metals and plastics was used to induce hemolysis in human blood. Durations of shear ranged from 4 to 5000 sec, thereby defining the overall hemolysis kinetics for the test materials. Data are presented as ΔC (relative plasma hemoglobin increase) vs. time t, and fitted to the relation ΔC = Atβ. It is found that A = A(β) and β is correlated with the critical surface energy of the plastics. Based on this evidence and reports of plasma protein adsorption, a partial explanation is proposed for shear‐induced hemolysis in this low‐stress regime (under 500 dynes/cm2).
Reaction of oral mucous membranes to selected dental materials
Authors: Lilly G. E. , Cutcher J. L. , Jendresen M. D. 
Published: December 2004

AbstractThis study was undertaken to evaluate the comparative reaction of oral mucous membrances to topical exposure to selected liquid dental materials. Elven adult mongrel dogs and five different liquid dental materials (50% citric acid, mercury, 50% phosphoric acid, eugenol and methyl methacrylate) were selected for this study. Each material was applied bilaterally to a specific area of the ventral surface of the tongue for 5 min. Sites were examined at 30 min and visual observations recorded. Animals were sacrificed 24 hr after application. hematoxylin and eosin stained microsections were examined without knowledge of the material used. Citric acid and phosphoric acid were associated with the most severe response, characterized clinically by surface necrosis and histologically by a dense, diffuse, neutrophilic infiltrate. Eugenol was associated with erythema, and in some cases, ulcers, with a moderate diffuse inflammatory infiltrate, histologically. Methyl methacrylate resulted in immediate surface dehydration followed by mild erythema with mild local inflammatory infiltration. Mercury produced no observable clinical or microscopic tissue response. This is a simple method for evaluating acute mucous membrane toxicity which may be used for screening liquid dental materials.
Amalgamation reaction of tin, silver, and dental alloy (Ag3Sn)
Authors: Okabe Toru , Ling Fu‐Wen , Hochman Robert F. 
Published: December 2004

AbstractThe reactions between liquid mercury and high purity tin, silver, and silver‐tin dental alloy (Ag3Sn) were studied at 30°C. Polyhedral‐shaped crystals formed both on the tin and Ag3Sn specimens, while no crystalites were detected on the surface of the silver. The crystals on the tin Surface were identified as γ2 by x‐ray diffraction methods. Electron microprobe data revealed that the polyhedral crystals which formed on the Ag3Sn consisted only of the silver‐mercury compound which dissolved a small amount of tin (Ag 28.5, Hg 71.1, Sn 0.4 wt. %). The diffusion profile for the Hg‐Ag3Sn system demonstrated that silver atoms migrate much faster than tin atoms in Ag3Sn, both at the surface and in the area close to the mercury‐penetrated grain boundaries. It is clearly demonstrated that the bulk and grain‐boundary diffusion of silver is a major factor in the clinical setting reaction of dental amalgam.
Artifical skin. II. Pluronic F‐127 silver nitrate or silver lactate gel in the treatment of thermal burns
Authors: Nalbandian Robert M. , Henry Raymond L. , Wilks Harvey S. 
Published: December 2004

AbstractPluronic F‐127 was found to be an effective base for the bactriocidal agent silver nitrate or silver lactate following 18–22% surface area full thickness thermal burns. Some protection was afforded by Pluronic F‐127 alone, attesting to its biological activity as an artificial skin. The bacteriocidal agents, however, further enhanced the effectiveness of the dressing as an artificial skin. No inhibition of skin growth and repair was noted and the dressing was equally effective against Psuedomonas aeruginosa and Proteus mirabilis. Indication that natural defense mechanisms in addition to surface infection needs attention was also noted. Conclusion was reached that Pluronic F‐127 is an ideal base for bacteriocidal agents in the treatment of full thickness thermal wounds. In addition, the Pluronic F‐127 dressing with silver nitrate or silver lactate showed promise as an effective biological artificial skin against electrolyte imbalance, heat loss, and bacterial invasion.
Subacute toxicity testing of biomaterials using histopathologic evaluation of rabbit muscle tissue
Authors: Turner J. E. , Lawrence W. H. , Autian J. 
Published: December 2004

AbstractA group of 12 materials was evaluated for tissue compatibility via a sequential histopathologic evaluation of the rabit muscle response to the implanted materials. Tissue samples were obtained daily for 7 days and weekly for 12 weeks to follow the time course of the response. Some cytotoxic samples revealed a rapid and marked response of relatively short duration, whereas others tended to produce a sustained or a long‐term, intermittent inflammatory and/or necrotic response. These effects also demonstrated the suitability of 7 days as a satisfactory time period for routine evaluation of rabbit muscle reaction to implanted materials. The histopathologic evaluation of the response was compared with a gross evaluation of the implant site and an independent test of the material by tissue culture (agar–overlay method).
Drug‐incorporated silicone discs as sustained release capsules. I. Chloroqine diphosphate
Authors: Fu J. C. , Kale A. K. , Moyer D. L. 
Published: December 2004

AbstractQuantitative investigation of the rate of diffusion (in vitro) of chloroquine diphosphate, an antimalarial drug, from silicone rubber (Silastic) discs is reported here. The viscosity of the polymer is reduced to facilitate the formation of a more homogeneous drug‐polymer mixture from which the discs are made. The average quantity of drug released daily from these vulcanized silicone rubber discs is measured as a function of the amount of drug initially incorporated in the polymeric mass. Discs with 9 and 36 mg of chloroquine diphosphate incorporated continue to release drug in microgram quantities for a period of over four months. The presence of low viscosity silicone fluid (20 centistokes) in the discs was found to cause no significant alteration in the drug release rate. The effect of agitation of the fluid in which the discs are immersed is also investigated. Results from samples prepared from different batches of polymer showed comparable results, indicating the rather homogeneous nature of the polymer‐drug system. All samples showed high release rates during the first few days followed by much lower and more or less constant drug release on subsequent days over a period of months.Concentrations of the drug in the eluant is determined spectrophotometrically by utilizing the 220‐ and 343‐mμ peaks of chloroquine diphosphate as well as spectrofluorometrically by measuring the percent fluorescence at 405 mμ (360‐mμ excitation).
Local reaction to polyurethane—a comparative study in the mouse, rat, and rabbit
Authors: Rigdon R. H. 
Published: December 2004

AbstractThe local reaction to polyurethane (Thurane foam‐rigid type) varies significantly in the subcutaneous tissue of the mouse, rat, and rabbit. Polymorphonuclear leucocytes concentrated at the periphery of the particles of polyurethane in the mouse in conspicuous numbers for as long as 550 days. In the rat leucocytes were infrequent and in the rabbit they were absent. The mechanism by which this variation occurs is unknown. It is suggested that it may be attributed to an electrical phenomena with variations in different hosts. There was an accumulation of pigment in the local inflammatory reaction apparently resulting from a degeneration of the polyurethane as well as degeneration of erythrocytes. The amount of this pigment varied significantly in the mouse, rat, and rabbit. Proliferation of large fibroblast‐like cells, apparently originating from adjacent striated muscle, occurred in the mouse but was absent in the rat and rabbit, another significant, variation in the reaction of the mouse to polyurethane when compared to that in the rat and rabbit.
Biological tolerance of ionogenic hydrophilic gels
Authors: Šprincl L. , Vacík J. , Kopeček J. 
Published: December 2004

AbstractThe long‐term biological tolerance of hydrophilic gels containing ionogenic groups was investigated on animals (rats and pigs). The basic polymeric skeletons of poly(glyco1 monomethacrylate) and poly (N‐ethyl methacrylamide) were modified by introducing acidic (carboxylic) and basic (tert‐amino) groups, or both groups at a time. Introduction of both groups at a time in the molar ratio yielded an electroneutral polymer of ionogenic character.In all groups investigated here the implant was encapsulated by a fine capsule of collagen fibrous tissue; no signs of proliferation were observed. No calcification took place.The second part of the work consisted in an investigation of the tolerance of heterogeneous poly(glyco1 monomethacrylate) gels containing ionogenic groups,basic, acidic, and ampholytic, with continuously changing porosity. The microporous polymers (50–60% water in the starting mixture) were healed‐in as compact gels by encapsulation with collagen fibrous tissue. The macroporous polymers (70% of water and more in the starting mixture) were encapsulated with a capsule of collagen fibrous tissue, from which newly formed capillaries,serous exudate and numerous cells penetrated into the implant. The more porous the material, the broader the zone of cellulization. In microporous polymers there was no calcification; in macroporous, calcification occurred in the margin of the implant or in its center. In contrast with other authors' findings,no effect of the chemical composition within the concentration range investigated upon the way of healing‐in or calcification could be observed; only the effect of physical factors was evident.
Thromboembolic sequelae to indwelling Silastic cannulas in sheep arteries
Authors: Andrews Edwin J. , Hughes Howard C. 
Published: December 2004

AbstractIn sheep, chronic arterial cannulation with Silastic has led to thrombus formation and to intimal fibroplasia of a type not previously reported. Concurrent infection resulted in septic embolization to the brains and eyes on the same side as the cannulated vessels. The histopathology is described in detail.
Use of organ cultures to evaluate biodegradation of polymer implant materials
Authors: Hegyeli Andrew F. 
Published: December 2004

AbstractAn in vitro organ culture method was developed for the study of biodegradation of surgical implant materials. This method gives valuable information in less than 24 hr in the case of rapidly biodegradable materials such as poly(lactic acids) and poly(alkyl 2‐cyanoacrylates). These data correlate well with the results of long‐term in‐vivo implantation studies. The organ culture technique can be used for the study of metabolism of polymers including the formation of volatile metabolites during biological degradation. Finally, histological and electron microscopic studies of the exposed organ slices can give indication of the formation of toxic metabolites during the biological degradation process.
Scanning electron microscopic study of surface changes on biodegradable sutures
Authors: Ruderman Robert J. , Bernstein Emil , Kairinen Eila , Hegyeli Andrew F. 
Published: December 2004

AbstractTopographical changes which occur during the degradation of suture materials were studied by scanning electron microscopy. Potentially absorbable sutures were compared with those known to be absorbable. Loops of plain catgut, chromic catgut, polylactic acid, polyglycolic acid, polyester “A” and polyester “B” were implanted subcutaneously in rats for periods ranging from 2 to 14 weeks. They were removed and examined without further treatment. Specific and localized structural defects were observed to develop in the implant materials. In some cases the time required for development of these defects indicated that although they can be assumed to play a role in the ultimate dissolution of the material, these flaws are not necessarily responsible for the early loss of mechanical properties which have been observed by others. The implications of these observations for the development and evaluation of synthetic surgical repair materials are discussed.
Biomechanical evaluation of bone‐porous material interfaces
Authors: Nilles J. L. , Coletti J. M. , Wilson C. 
Published: December 2004

AbstractAn investigation was undertaken to correlate mechanical strengths of various bone‐porous material interfaces with the type and degree of osseous ingrowth. Intracortical cylinders of porous and nonporous metals, ceramics, polymers, and carbon were implanted into canine long bones and examined at 3, 6, and 12 weeks. Reflected and transmitted light microscopy were used to study bone ingrowth. Electron microprobe analysis and tetracycline labelling were used to characterize the degree of mineralization of the ingrowth. Shear strengths of bone‐porous material interfaces were measured on cylinders forced out in compression. Microhardness traverses were made across the interfaces. Readily identifiable bone was shown by histology in many porous specimens. Mineralization was found to various depths in all the porous specimens. The porous metals displayed the greatest interfacial shear strengths and hardnesses, with values from one‐ to two‐thirds that of cortical bone. Changes occurred in the ingrowth region, a bone‐metal composite, which suggest a reduction of elastic mismatch.
Estimation of the permeability of cellulosic membranes from solute dimensions and diffusivities
Authors: Farrell Peter C. , Babb Albert L. 
Published: December 2004

AbstractPermeability data were obtained for commercial regenerated cellulose (Cuprophan PT–150) in isotonic saline at 37°C in a dual closed‐loop dialysis cell. Eighteen radioactively labeled monodisperse solutes of widely differing chemical and physical properties, and ranging in molecular weight from 60 (urea) to 1355 (vitamin B12), were evaluated and the permeabilities of these solutes have been successfully correlated with various solute characteristics.Correlations were established between membrane mass transfer resistances (or effective membrane diffusivities) and:(1) characteristic molecular radii determined from both molal volume at normal boiling point (MVNBP) and hydrodynamic theory and (2) molecular diffusivities in saline. Membrane resistance data reported elsewhere for other cellulosic membranes were also found to correlate well with both MVNBP radii and liquid diffusivities.The correlations for Cuprophan have the following form:

where Deff = effective membrane diffusivity (cm2/sec), r2 = MVNBP radius (Å), and Ds is saline diffusivity (cm2/sec). Similar correlations were established for other membranes. It should be feasible to use these and similar correlations to predict membrane permeabilities (for a given membrane) from known solute characteristics without resorting to laboratory measurements.Membrane activation energies were also computed for eight solutes by measuring the variation in permeation rate through Cuprophan between 5 to 50°C. Unexpectedly, it was observed that the solute activation energies were not dominated by the activation energy of the membrane but revealed significant differences between solutes.
The effect of movement on the bonding of porous metal to bone
Authors: Cameron Hugh U. , Pilliar Robert M. , Macnab Ian 
Published: December 2004

AbstractAn attempt has been made to define the conditions with respect to movement under which porous metal will bond to bone. It has already been shown that bone will grow into the pore of porous Vitallium under static conditions and under conditions of micromovement, as when stressed by the pull of a tendon. An experiment is described in which porous Vitallium staples were inserted across an unstable osteotomy site. No bonding occurred indicating that bone ingrowth will not occur in the presence of movement of this order of magnitude.The implication of this observation in the design of porous coated endoprostheses is that some form of initial mechanical fixation is required, and this fixation must remain rigid for four months to allow bone ingrowth.