bluuebunny/crossref_metadata_2025_split huggingface dataset:
A composite model of the elastic behavior of dental amalgam
Authors: Katz J. Lawrence , Grenoble Dale E. 
Published: December 2004

AbstractA model describing the elastic behavior of dental amalgam as a composite material has been developed using elastic theory for quasi‐homogeneous, quasi‐isotropic systems. The elastic constants of the composite amalgam can be computed using Voigt‐Reuss and Hashin‐Shtrikman methods if the relative volume fractions and the elastic constants of the constituent phases are known. This model also relates the elastic behavior of the amalgam to manipulation during preparation. The elastic constants of several spherical and cut amalgams, as well as the constituent γ, γ1, and γ2 alloys, have been measured in the 0–50 kilobar range using a solid media pressure apparatus and an ultrasonic interferometer. High pressure studies are necessary so that the effects of porosity can be assessed. Calculations based on this model include the effects of porosity as well as the Hg content.
Survey of materials for hard‐tissue prosthesis
Authors: Levine Sumner N. 
Published: December 2004

AbstractThe properties of the three main classes of orthopedic alloys (316L steel, Co‐Cr alloys and titanium) are discussed, while all show good general corrosion resistance, the 316L steel have a tendency toward crevice corrosion. Fatigue fracture due to poor design and fabrication defects is discussed. A summary of some problems associated with the evaluation of tissue response is presented. Finally, a review of several new trends toward achieving tissue adhesion is presented.
Some requirements and problems in tissue interfacing
Authors: Ghidoni John J. , Hall C. William 
Published: December 2004

AbstractInterfacing biologic material with foreign substances is a problem common to all implantable devices. This paper discusses these problems with respect to degradation of the material used in fabrication and the body's reaction to the foreign substance. The requirements dictate the type of tissue reaction sought and this in turn determines the base material. A nonreactive material may be ideal for one set of needs but tissue reactivity would be required for another. The specialized tissue “blood” is given special emphasis.
Bone formation and the response of bone to implant insertion
Authors: Mathews Robert S. 
Published: December 2004

AbstractThis basic introductory discussion has sought to outline the embryology and development of bone and has stressed both its function and structure. I have, also, outlined the sequence of fracture healing and discussed some of the problems of implant acceptance in the musculoskeletal system. With this information, I hope you as basic scientists will be able to better understand some of the problems our patients pose with respect to implant design and function. It should be reiterated that many men have contributed to this very vital and important field of Orthopedic Surgery. Moreover, I would like to stress that not withstanding the complications previously discussed, the availability of biologic and metallic implants has contributed immensely to the high level of patient care we know today; and they have a very important role in the future improvement of our ability to care for our patients.
Initial surface interaction of blood and blood components with Al2O3 and TiO2
Authors: Hulbert S. F. , King F. M. , Klawitter J. J. 
Published: December 2004

AbstractThe success of material implants in the vascular system has been limited by the fact that the intial events of blood coagulation on foreign material surfaces are not understood. Many materials have been evaluated in the search for a suitable implant material in this system. Recent success of porous ceramic materials in bone‐ceramic compatibility studies stimulated the feeling that these materials should be tested in other body tissues such as the blood.Ceramic disks of Al2O3 and TiO2 were evaluated using a contact angle measurement technique to determine the characteristics of these material surfaces before and after exposure to a blood environment. This technique involved measuring the contact angle of sessile drops of various liquids on these surfaces with a microscope fitted with a goniometer eyepiece. By plotting these contact angles according to the procedure of Zisman, the characteristics of the surfaces could be evaluated.The clean ceramic disks were found to be extremely wettable even after exposure to a physiological saline environment. On exposure of these disks to a blood environment, it was observed that some type of film was adsorbed from the blood onto the ceramic surface during the initial minutes of exposure. This film had wetting characteristics consistent with layers of fibrinogen.
Bonding mechanisms at the interface of ceramic prosthetic materials
Authors: Hench L. L. , Splinter R. J. , Allen W. C. , Greenlee T. K. 
Published: December 2004

AbstractThe development of a bone‐bonding calcia‐phosposilicate glass‐ceramic is discussed. A theoretical model to explain the interfacial bonding is based upon in‐vitro studies of glass‐ceramic solubility in interfacial hydroxyapatite crystallization mechanisms, compared with in‐vivo rat femur implant histology and ultrastructure results.
Ceramic tooth implants
Authors: Young Franklin A. 
Published: December 2004

AbstractFor many years man has engendered the idea of replacing lost or unserviceable teeth with natural or artificial substitutes has, however, only recently been shown to offer a viable alternative to externally attached prostheses. Ceramics were selected which have demonstrated compatibility with long bones and optimization of the ceramic properties was undertaken. Implants were made in the jawbones of adult dogs. Both tooth root replicas and crown‐root combinations were employed. Anchorage of the implants was found to range from stable attachment to rapid exfoliation. The calcium aluminates were found to possess barely adequate mechanical strengths.This research suggests that these ceramics can function as effective tooth roots if the proper designs and surgical techniques are employed. Sufficient evidence of tissue compatibility has been amassed to warrant further study.
The complex factors in tooth implantation
Authors: Hamner James E. , Reed O. M. 
Published: December 2004

AbstractThe criteria for an ideally successful tooth implant should inlcude: (1) stable physiologic retension, (2) non‐toxicity, (3) durability and sound function in the oral cavity, (4) non‐carcinogenicity, and (5) esthetic satisfaction.Many complex factors such as the anatomic site itself (the tooth socket), proper healing of the periodontium, viability of the periodontal membrane in tooth reimplants, the oral microbial flora, the general health of the implant recipient, non‐traumatic occulsion, physical and chemical properties of artificial implant material, and adequate stabilization influence the success of a tooth implant.Initial results demonstrate that ceramic (calcium aluminate) tooth implants with a 50 to 75‐μ porosity appear to more promisingly meet the criteria for successful artificial tooth implantation than implants fabricated from plastic (polymethylmethacrylate), which produced osteomyelitis in 5/21 jaw block specimens in baboons with complete lack of true periodontal attachment between alveolar bone of the implant socket and the plastic tooth implant, shown microscopically and ultramicroscopically.
Bioceramics and dentistry
Authors: Garrington George E. , Lightbody Philip M. 
Published: December 2004

AbstractMetals and polymers have received considerable attention with respect to their potential use in human implantation. Serious study of the ceramics for this purpose has only recently begun. Materials for implantation in any body site must meet certain requirements. Each class of material has been found to have some highly desirable properties as well as some undesirable characteristics. Materials for use in dental implantation, particularly for the replacement of individual teeth, are subjected to environmental factors not generally existent in other implantation sites. Preliminary studies of the ceramics have suggested that, from the physiologic standpoint, they may be the best implantable substitute for hard tissues (bones and teeth) yet achieved. There are, however, many questions remaining to be answered concerning the selection of the most suitable material, its fabrication, and the reaction of tissues to it. These questions should serve to indicate future areas of exploration.
Mechanical properties of a hydrophilic acrylic polymer
Authors: O'Brien W. J. , Hermann J. , Shepherd T. H. 
Published: December 2004

AbstractAcrylic polymers with hydrophilic groups (i.e., ethyl hydroxyl) may be prepared that convert to a soft elastic gel by absorbing water. Such a polymer has been applied to dentistry for use as an elastic lining material for dentures. A commercial product, Hydron, was used in this study. The linear expansion of this material after 520 hr of water immersion was found to be 20.4%. Hardness was found to decrease from 15.7 KHN for the dry polymer to 1.5 KHN at 19% absorbed water content. The swelling pressure was measured and found to reach a maximum value of 157 psi after 204 hr of water immersion. The Young's modulus was found to decrease from a value of 295,300 psi to 290 psi with 19% absorbed water content. Values were determined on intermediate water contents for the properties studied.
Screening and evaluation of materials for thromboresistance
Authors: Wallin Richard F. , Krisik Mildred 
Published: December 2004

AbstractTwo methods are described for evaluating the thromboresistance of materials available as tubing. In the first method lengths of the tubing containing canine blood were incubated at 37°C, opened at timed intervals and examined for clots. For all materials tested, mean clotting times ranged from 5.2 min for glass to > 300 min for silicone rubber treated with GBH, TDMAC‐heparin or TDMAN‐heparin. For most materials, in vitro clotting times ranged from 20 to 60 min. Further testing in vitro indicated that heparin was more firmly bound to silicone rubber as TDMAC‐heparin than as GBH. In the second method, short segments of tubing were surgically placed within the femoral veins of anesthetized dogs, examined for patency after 2 hr, removed and examined for thrombi. None of the materials tested appeared completely thromboresistant by the 2 hr in vitro method. Tubes of glass or unheparinized materials were usually completely occluded at the end of the test; silicone rubber treated with TDMAC‐heparin apperared relatively thromboresistant. Results of in vitro and in vivo testing were generally in good agreement and were consistent with the known thromboresistant properties of materials.
The monsanto polyacrylonitrile hollow‐fiber artificial kidney
Authors: Salyer I. O. , Ball G. L. , Beemsterboer G. L. , Leonard R. L. , Merrill J. T. , Hampers C. L. , Lowrie E. G. 
Published: December 2004

AbstractAdvantages of a hollow‐fiber hemodialyzer have been well described. The goal of this program was to provide a working model of a noncellulosic hollow fiber artificial kidney with nonthrombogenic blood‐contacting surfaces, low blood‐priming volume and low pressure drop, a satisfactory rate of urea transport, and high rate of ultrafiltration of water. Also, the reliability and utility of these devices was to be demonstrated through clinical evaluation.
The effect of cleaning an experimental spherical Ag3Sn alloy on the tensile strength and fracture of dental amalgam
Authors: Young F. A. , Wilsdorf H. G. F. 
Published: December 2004

AbstractExperiments have been conducted with the aim of improving the tensile strength of dental amalgam. Anticipating a surface contamination of Ag3Sn, the powder was washed with 5% HCl before amalgamation. The resulting amalgam showed a considerable decrease in the scatter of strength data and an increase in fracture stress. At 40 w/o mercury content the strength increase was found to be 40%. The reason for this substantial improvement in the strength of dental amalgam was revaled by electron fractography. It was found that the bond between unconsumed Ag3Sn particles and the amalgam matrix had been strengthened to such an extent that fracture took place through the silver‐tin particles, which allowed Ag3Sn to perform its role as the strongest component in a dispersion hardened system.
An enzyme histochemical approach to the evaluation of polymers for tissue compatibility
Authors: Salthouse Thomas N. , Willigan Donald A. 
Published: December 2004

AbstractNine samples of plastic, including PVC stabilized with various amounts of organotins, silicone rubber, PTFE, polyethylene, polypropylene, and a U.S.P. negative control high density polyethylene, were implanted in rat gluteal muscle. Frozen sections were cut in a cryostat microtome and treated for enzyme histochemical reactions. These included succinic dehydrogenase, acid phosphatase, aminopeptidase and adenosine triphosphatase. The results illustrate that enzyme histochemical data can be of value in supplementing other methods in the evaluation of polymers for tissue compatibility.
Inorganic heparin complexes for the preparation of nonthrombogenic surfaces
Authors: Dyck Manfred F. 
Published: December 2004

AbstractThe surfaces of many plastics and other materials of interest in the fabrication of implants can be made nonthrombogenic by treating them with an inorganic heparin complex (IHC) system consisting essentially of a soluble metal salt, a solvent, and heparin. During complexing, the metal salt polymerizes at the same time it is trapped in the collapsing matrix of the surface; the entrapped inorganic polymer then reacts with heparin, probably by chelation. Treatment with an IHC system is not known to alter the mechanical or physical properties of the treated material. If desired, the surface can be made radiopaque by incorporating bismuth chloride or other contrast salts during complexing. After treatment, the surface can be autoclaved or sterilized with ethylene oxide. Materials that have been made nonthrombogenic by the IHC system include Silastic, polyurethane, cellulose acetobutyrate, polymethylmethacrylate, nylon, polyethylene, polypropylene, polyethylene‐vinyl acetate, polystyrene, natural rubber, and polyvinyl chloride.
Effect of pressure on heat transport in polymers used in dentistry
Authors: Chen R. Y. S. , Barker R. E. 
Published: December 2004

AbstractThe thermal properties of dental materials are important in certain aspects of tooth repair and the restoration of dental function. This is especially true for polymeric dental materials, for which low thermal conductivity is often considered an important asset. This paper contains a report on the surprisingly large effect that pressure (well with in the range encountered on the biting surfaces of teeth) can have on heat transfer in polymers that are widely used in dentistry. A sandwich type pressure‐conductivity cell has been used to measure the thermal conductivity K of polystyrene, polymethyl methacrylate, polyethyl methacrylate, and poly‐n‐butyl methacrylate. The measurements span the range −50 to 50°C and pressures up to 2000 bar. For the polymers mentioned (and many others) K at a given temperature increases as pressure is increased. Initial increases in pressure to several hundred bars may typically increase the over‐all heat transfer coefficient by a factor of two or more. At higher pressures, the relative slope (dK/dp)/K is typically about 10% per kilobar. Some comments are made about the thermal contact coefficient and the thermal diffusivity which are of more direct interest to dentists than K itself.
Corrosion of Ti‐6Al‐4V in simulated body fluids and bovine plasma
Authors: Aragon P. J. , Hulbert S. F. 
Published: December 2004

AbstractThe corrosion of Ti‐6Al‐4V at 37°C in several simulated body fluids and bovine plasma was studied using the passive current‐time technique. A 0.9% NaCl (bw)‐0.1 N NaH2PO4 solution gave results closest to those using bovine plasma as an electrolyte.All of the samples showed an activation period of 10–15 hr, after which an increase in the corrosion rate was observed. Several possible explanations for this effect are given.For comparison, a sample of Type 316 L stainless steel was tested using isotonic saline solution as the electrolyte. Both the initial and final current densities were considerably higher than those for Ti‐6Al‐4V indicating a corrosion rate considerably higher for the Type 316 L stainless steel.
A new method for evalution of antithrombogenicity of materials
Authors: Imai Yohji , Nose Yukihiko 
Published: December 2004

AbstractA new method was developed for evaluating kinetically the antithrombogenicity of materials. The amount of thrombus formed was measured gravimetrically at an appropriate interval of time after calcium chloride was added to ACD blood in contact with a test material. Graphic curves for thrombus formation on glass, Silastic, Hydron, and treated natural tissues were obtained and compared. There was good correlation between our in vivo tests and in vivo observations.
In vivo testing of silicone rubber joint implants for lipid absorption
Authors: Meester Walter D. , Swanson Alfred B. 
Published: December 2004

AbstractSilicone rubber implants removed from patients undergoing revision arthroplasty were examined for breakage and cracks and analyzed for lipid content. No relationship was observed between lipids extracted from the implants and the implantation time. Neither was the absorption of lipids and the incidence of breakage of the implants found to be related. Various factors contributing to the possible failure and breakage of the joint implants are discussed.
Degradation of poly(methyl 2‐cyanoacrylates)
Authors: Wade Clarence W. R. , Leonard Fred 
Published: December 2004

AbstractMethyl 2‐cyanoacrylate‐2‐14C, ‐3‐14C and ‐14CN tagged monomers were im planted subcutaneously in mongrel dogs and their urine assayed for radioactivity. The results show that the urea from the ‐3‐14C was radioactive and radioactive acidic components, as well as neutral moieties, were present. Urea recovered from the urine of animals in which the ‐2‐14C and ‐14CN methyl 2‐cyanoacrylate were implanted was only very slightly radioactive. The data are consistent with the hypothesis that hydrolytic chain scission and ester hydrolysis may be involved in the degradation of 2‐cyanoacrylates in vivo.
The elastic properties of hard tissues and apatites
Authors: Grenoble Dale E. , Katz J. Lawrence , Dunn Karl L. , Gilmore Robert S. , Murty K. Linga 
Published: December 2004

AbstractThe pressure dependence of the elastic constants of various halides, hard tissues and synthetic apatites have been examined in the 0‐ to 50‐kilobar range using a solid media, pressure apparatus coupled with an ultrasonic interferometer. The samples includ: hydroxy‐, fluor‐, and chlor‐apatite, NaCl, CaF2, mollusc shell (aragonite), ivory, dentin and enamel, and fish, bovine, and human bones. High pressures were used in order to assess the effects of porosity in aggregate samples and to make measurements on specimens of ideal density. Computer analysis of the measured longitudinal and shear ultrasonic velocities yields the pressure dependence of the bulk, shear, and Young's moduli and Poisson's ratio. Atmospheric pressure values at ideal density are obtained by back extrapolation from the high pressure measurements.
Ceramic root implantation in baboons
Authors: Hamner James E. , Reed O. M. , Greulich Richard C. 
Published: December 2004

AbstractWhen a human natural tooth is evulsed and lost, replacement by implantation of a replica would be one logiclal treatment choice. Identification of an appropriate biomaterial which would allow the replica tofunction in a stable manner without eliciting a toxic response is one of the major challenges facing dentistry today, and has been the subject of an increasing number of investigations in recent years.Because of questions which still remain regarding the biocompatibility of candidate materials, extensive animal research in tooth implantation is an absolute necessity. Primates, providing dental models closely approximating the human condition, are especially valuable for undertaking that systematic scrutiny of experimental implant materials which is so clearly prerequisite to human clinical trials.In the present study, 22 calcium aluminate roots were implanted into fresh natural tooth extraction sites in 10 baboons for periods ranging from 2 weeks to 10 months. The controlled porosity of the ceramic roots varied from 50 to 200 μ.Implant retention and stability, resulting from adequate ingrowth of fibrous/vascular elements into the ceramic pores with subsequent mineralization therein of newly formed osteoid matrix, were optimal when the calcium aluminate root implants had a porosity of 100–200 μ.Calcium aluminate root implants so successfully met all criteria of tissue adherence and host acceptance in the present short‐term study that their application in basic and clinical studies in man seem fully warranted at this time.
Biopolymers as biomaterials: Mechanical properties of γ‐benzyl‐L‐glutamate‐L‐Leucine copolymers
Authors: Anderson James M. , Hiltner Anne , Schodt Kathleen , Woods Richard 
Published: December 2004

AbstractA seires of γ‐benzyl‐L‐glutamate‐L‐leucine copolymers were prepared and cast films of the copolymers were subjected to dynamic mechanical and stress‐strain tests. Dynamic mechanical testing revealed that the copolymers had a molecular relaxation at about 50°C and that the magnitude of this relaxation was directly proportional to the molar concentration of glu(OBz) in the copolymer. The magnitude of the 50°C relaxation was also dependent upon orientation. The stress‐strain behavior of the copolymers was examined before and after PECF treatment. Prior treatment with PECF caused in increase in the tensile strength to failure and a decrease in the elongation at failure. Increasing concentrations of leu caused the tensile strength to failure to increase. Efforts to degrade the films by refluxing 6 N HCl and enzymic attack were unsuccessful and suggested that these copolymers could find use as biomedical materials.
Biocompatible materials for use in the vascular system
Authors: Grode Gerald A. , Falb Richard D. , Crowley James P. 
Published: December 2004

AbstractTechniques are presented which result in the production of thromboresistant materials which can be used to interface with blood in the vascular system. Three useful processes for the heparinization of materials are presented and data are given on characteristics of attachment, the blood compatibility, and environmental stability of these surfaces. At this point, applications of heparinized surfaces via a simple one‐step process should be limited to siturations where low blood shear rates are involved, such as the venous system. Intitial data indicate significant loss of surface heparin in situations where high blood flow rates are involved such as A‐V shunts.
Porosity in silver‐tin amalgams
Authors: Taylor Duane F. 
Published: December 2004

AbstractPorosity has been determined metallographically for a series of spherical silvertin amalgams. The alloy consisted of separate size fractions of five compositions. Porosity was found to increase with increasing silver content and particle size, and was reduced by blending of large and small particle sizes. In blended alloys the porosity showed close correlation to the observed setting expansion.