bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled release of testosterone using silicone rubber
Authors: Shippy Ronald L. , Hwang Sun‐Tak , Bunge Raymond G. 
Published: December 2004

AbstractThis study was undertaken to find a means for a long lasting and uniform release of the male hormone, testosterone. The rate of release of testosterone was determined over periods up to 4 months. The factors which affect the rate of testosterone release were studied and a mechanism for the release of testosterone was proposed.The first means providing a constant release of testosterone was the use of silicone rubber membrane around testosterone cylinders. It was found that a constant rate of release was reached after an initial unsteady state period ranging from 1 to 2 weeks.It was theorized that a water layer had formed between the membrane and testosterone cylinder. This layer caused the concentration inside the capsule to be that of saturated water.Several testosterone cylinders were coated with especially prepared membranes. These membranes were made by dissolving testosterone and silicone rubber in a mixture of tetrahydrofurane and toluene. It was hoped that an amount of testosterone might be incorporated into the silicone rubber matrix. The samples were run and the permeabilities determined. The permeability showed little or no increase over the range of 10–30% testosterone.Next, a membrane was prepared by mechanically mixing testosterone and silicone rubber. The amount of testosterone ranged between 5 and 200%, by weight. A definite increase in the permeability was observed with an increase in the percentage of testosterone.The second method of obtaining a uniform rate of release of testosterone was by mechanically mixing testosterone and silicone rubber and molding a sheet. After an initial unsteady state a constant rate of release was obtained and such rate of release increased with higher percentages of testosterone in the sheets.
Biological tolerance of poly(N‐substituted acrylamides)
Authors: Kopeček J. , Šprincl L. , Bažilová H. , Vacík J. 
Published: December 2004

AbstractThe biological tolerance of poly(N‐substituted acrylamides) implanted subcutaneously to rats and pigs was investigated. Besides a macro‐ and microscopical evaluation of the implant and its surroundings, the surface changes of the implants were determined by means of a Stereoscan electron‐optical microscope;the results obtained confirmed the very good in vivo stability of the polymers used.The histological analysis showed that all the polymers under investigation are very well tolerated by the organism and do not provoke any unfavorable reaction. The implants become surrounded with a granulation tissue which is gradually replaced by fibrocytes and collagen fibers situated in the basic substance staining positively with the alcian blue and PAS. In contrast with some authors we did not find a thicker capsule surrounding the implant on the sharp edges but on the flat planes. No calcification could be observed within the intervals investigated. The surface changes, which were studied electronoptically, were insignificant and connected with the way in which the implant was treated. No indications of malignant growth were observed.
Resorption rate, route of elimination, and ultrastructure of the implant site of polylactic acid in the abdominal wall of the rat
Authors: Brady John M. , Cutright Duane E. , Miller Robert A. , Battistone Gino C. , Hunsuck Ervin E. 
Published: December 2004

AbstractThis experiment describes resorption rate, light and electron microscopic appearance of the implant site, and tissue distribution and route of elimination of radioactivity from carbon‐labelled polylactic acid implants. Fifty‐six rats received abdominal implants and were serially sacrificed at 28, 56, 84, 112, 140, 154, and 168 days. Urine and fecal output was measured for radioactivity, along with implant site and several tissues at the time of sacrifice. Tissue distribution of activity was negligible. Resorption rate of the implant was linear with 63.2% remaining after 168 days. Elimination of radioactivity was via respiration, approximately 29.4% by this route. Histologically, the implant was invaded rapidly along septal defects or slowly on broad fronts. Invading cells were characterized either by large double‐walled vacuoles or by large accumulations of mitochondria and microvesicles adjacent to the implant surface. The long duration of this type of implant may be an important consideration in surgical applications.
Diffusion of pyrimethamine from silicone rubber and flexible epoxy drug capsules
Authors: Fu J. C. , Kale A. , Moyer D. L. 
Published: December 2004

AbstractThe rate of diffusion of pyrimethamine, a pyrimidine‐based antimalarial drug, from silicone rubber is compared to the diffusion of this drug from a flexible epoxy. Specific amounts of drug were mixed into the epoxy resin prior to the addition of an aliphatic diamine curing agent in the reparation of the epoxy‐drug capsules and into the silicone rubber prior to vulcanization with stannous octoate in the preparation of silicone drug capsules. These capsules, in the form of discs, were separately immersed in water which was replenished at regular time intervals. The amount of drug released was determined spectrophotometrically (λ max = 275 mμ). Silicone rubber discs with 20 mg of drug incorporated/disc showed a much higher initial release rate than epoxy discs with an equivalent amount of drug incorporated. The rate of drug release is shown to be a nonlinear function of the amount of drug initially incorporated. The amine functional groups on pyrimethamine, and the possibility of its participation in the curing of the epoxy is noted. In silicone rubber, such interaction is not expected. The addition of a silica filler to the epoxy drug mixture is associated with greater uniformity in the observed drug release rates of capsules made from the same batch of polymer drug mixture. The Shore A durometer hardness of these drug capsules are 30 and 70 for silicone rubber and epoxy, respectively.
Transport through crosslinked poly(2‐hydroxyethyl methacrylate) hydrogel membranes
Authors: Ratner Buddy D. , Miller Irving F. 
Published: December 2004

AbstractThe transport of urea and other biologically interesting solutes in aqueous solution across poly(2‐hydroxyethyl methacrylate) (p‐HEMA) hydrogel membranes has been studied. The results show that p‐HEMA membranes have a high permeability to urea due to a strong interaction between the polymer and urea, and, in addition, they are consistent with a pore flow model in which solute transport takes place through water‐filled regions essentially unaffected by the surrounding polymer matrix. The results indicate that such p‐HEMA membranes might be suitable for hemodialysis applications.
Poly(vinyl alcohol) hydrogels for synthetic articular cartilage material
Authors: Bray James C. , Merrill Edward W. 
Published: December 2004

AbstractAs part of a program to develop a synthetic articular cartilage material for use in reconstructive joint surgery, this paper is concerned with the desiderata for such a material and with the properties of poly (vinyl alcohol) hydrogels reinforced by crystallinity as developed for this purpose. Reference is further made to the ultimate preparation of cationic PVA hydrogels to provide the low‐friction lubrication necessary in a cartilage prosthesis when in contact with natural synovial fluid.
Preparation of dental alloy by splat cooling
Authors: Johnson Lewis B. 
Published: December 2004

AbstractSplat cooling has been used for the preparation of dental alloy in the form of ribbons of 5–25 μm in thickness. The powdered alloy was produced by shaking the ribbons with a dental pestle in a mechanical amalgamator. One minute shaking produced a powder all of which passed a standard 400 mesh sieve. Only phases expected at room temperature have been produced thus far.
Porous segmented polyurethanes—possible candidates as biomaterials
Authors: Wilkes Garth L. , Samuels Sam L. 
Published: December 2004

AbstractA systematic series of chemically well defined, segmented polyurethane‐polyether copolymers and their mixtures are shown to develop predictable and controlled morphologies. Changes in compositions and casting histories allow the preparation of polymer films with various types of morphological structures including uniform nonporous, coalesced spherulitic nonporous, spherulitic porous, and “Swiss cheese‐like” structures with uniform (but alterable) pore sizes.The desirability of producing biocompatible materials with controlled morphologies provides incentive for further investigation of these and similar urethane copolymers.
Development of a toxicity evaluation program for dental materials and products. II. Screening for systemic toxicity
Authors: Lawrence W. H. , Malik M. , Autian J. 
Published: December 2004

AbstractA series of systemic toxicity tests for various types of compounds are presented with illustrative data and discussed in regard to their relevance as potential screening tests for dental compounds and products. In developing and marketing a new dental material, it is important not only to ensure safety for the patient but also for the dentist, dental assistant, and laboratory worker who routinely handles and uses the product. Data are presented on a number of commercially available dental products as well as various chemical entities, which were tested by one or more of the methods described.
Plastics and inflammation: An in vivo experimental study
Authors: Rigdon R. H. 
Published: December 2004

AbstractA significant variation occurred in the inflammatory response to polyethylene and polyurethane when embedded subcutaneously in experimental animals. This variation apparently is related to the composition of the plastic and adsorption of proteins. The attraction of polymorphonuclear leucocytes by plastics apparently is related to the electrostatic and/or electrokinetic imbalance that occurs at or near the site of implantation.Polyurethane and polyethylene were selected for this study since preliminary observations had shown a variation in inflammatory response when they were embedded subcutaneously in the mouse. From this study it is evident that: (1) variations occurred in the inflammatory reaction in the subcutaneous tissue of mice and rabbits following the embedding of polyethylene and polyurethane; (2) polymorphonuclear leucocytes began to emigrate within hours after these two plastics were implanted, reaching their maximum number within 24 to 48 hr; (3) polymorphonuclear leucocytes usually were absent after the 6th experimental day in mice with polyurethane, but were present for 232 days in mice with polyethylene; (4) polymorphonuclear leucocytes were present in the rabbit for only a few days following subcutaneous implantation of polyethylene and polyurethane; and (5) leucocytes around the implanted polyurethane in the rabbit began to degenerate within 48 hr. The mechanism for this degeneration is not known.
A quick screening test of biomaterials by means of chick embryo techniques
Authors: Hulbert S. F. , Klawitter J. J. , Bartles D. M. 
Published: December 2004

AbstractMany types of materials are being used as biomaterials, and there is a continuing search for more and better materials for specific pur poses. In this investigation, a new method was employed in screening materials in an effort to cut costs, save time, and have a worthwhile indication of the prospect of a new material. Samples of twenty gauge wires of stainless steel 316, stainless steel 304, Titanium 40, Vitallium, and copper were introduced into leg or wing muscles of 18‐day‐old chick embryos.This was accomplished by opening the egg shell with a dental drill, implanting the material, and reclosing the shell. The chicks were allowed to hatch and were later sacrificed after eleven days, giving a total implant time of 14 days. This time period allowed for the acute inflammation that occurred during wound healing to subside. The sections were retrieved, embedded in epon 812, sectioned with a diamond saw, and histologically evaluated.Copper was used for the negative control and showed the greatest adverse tissue response. Titanium 40 showed almost no response and stainless steel 316 showed very little. Stainless steel 304 exhibited a somewhat greater response than the stainless steel 316. All of the materials except wrought Vitallium used in this experiment gave predicted results.
Biocompatibility of poly(2,4‐pentadiene‐1‐ol)
Authors: Ulbrich K. , Šprincl L. , Kopeček J. 
Published: December 2004

AbstractIn our earlier papers1–4 we reported on the biocompatibility of esters and substituted amides of methacrylic and acrylic acids which are suitable for the development of specific biological functions.5 The results described in these papers1–4 enabled some relationships to be formulated which exist between the chemical and physical structure of the implants, on the one hand, and the process of their healing‐in and calcification, on the other.6.A number of biological applications require materials having rubber‐like mechanical properties. With this aim we started in our laboratory the development of hydrophilic elastomers based on dienes containing hydrophilic groups. Poly(2,4‐pentadiene‐1‐ol)7 was the first polymer of this type obtained which had mechanical properties suited for biomedical applications. Its biocompatibility with living tissue is reported in this paper.
Formation of platelet aggregate emboli in a prototype hollow fiber membrane oxygenator
Authors: Dutton Robert C. , Edmunds L. Henry 
Published: December 2004

AbstractWe examined the formation of platelet aggregate emboli and factors that affect platelet aggregate formation and embolization in prototype hollow‐fiber membrane oxygenators used to perfuse dogs. Platelet aggregates formed on the inlet surface of the oxygenator. Many aggregates subsequently formed emboli which passed through the fibers and sometimes lodges in them. Aggregates also developed on the outlet surface. Aggregates that adhered to the oxygenator surfaces contained tightly packed platelets having multiple pseudopodia extracellular granules, and occassional fibrin strands and white cells. The number of platelet aggregate emboli found downstream to the oxygenator varied between 0 and 4 emboli/ml blood. These emboli did not contain fibrin and extracellular granules. Platelet aggregate formation and embolization was reduced or eliminated by increasing the dose of heparin or by using a circuit with a large priming volume of albumin solution and a large surface area oxygenator.
Metallographic examinations of retrieved intramedullary bone pins and bone screws from the human body
Authors: Gray R. J. 
Published: December 2004

AbstractSubstantial improvements have been made by the surgical manufacturing industry in the development of implants and by the orthopedic surgeon in the use of prosthetic appliances. In spite of these advancements, some prosthetic devices completely fail of do not provide satisfactory performance. Hostile environmental conditions of the human body are highly influential in limiting the service life of the implants, so the material selection and the design and fabrication must be made with extreme care. Examinations we have made of intramedullary pins retrieved from femurs reveal examples of fretting and/or crevice corrosion and in‐service failures that nucleated in microscopic surface gouges. Self‐tapping screws, essential for securing bone implants, failed due to fractures originating in the thread roots. Failures by merely exceeding the ultimate strength of the material and by the more involved process of stress corrosion cracking are shown.An evaluation laboratory for failure analyses of prostheses is recommended.
Histochemical responses at a biomaterial's interface
Authors: Hench L. L. , Paschall H. A. 
Published: December 2004

AbstractA series of nonporous glasses and glass materials designed with controlled surface ion activities to allow chemical bonding to bone are described. Surface reactivities of these materials in vitro are correlated with biological activities in vivo and in tissue culture. Direct chemical bonding of the materials to bone is demonstrated. The mechanism for development of this bond is through the production of an amorphous ion surface gel on the bioglass. This gel induces osteogenesis by a chemotactic response of osteoblasts.
Principles governing biomolecule interactions at foreign interfaces
Authors: Hoffman Allan S. 
Published: December 2004

AbstractThe adsorption, conformational changes, and desorption of biological molecules at foreign interfaces are effected by both kinetic and thermodynamic factors. The thermodynamic factors which drive the biomolecule/foreign interface system towards equilibrium include the enthalpy and entropy changes occurring during each step in the adsorption process. The principles governing interaction of proteins with nonwettable (nonpolar) and wettable (polar) foreign interfaces are discussed in terms of these thermodynamic parameters. Some examples to illustrate these arguments are presented are presented for plasma‐protein interactions on Silastic and radiation‐grafted hydrogel/Silastic interfaces.
Effect of stress on tissue ingrowth into porous aluminum oxide
Authors: Hulbert S. F. , Matthews J. R. , Klawitter J. J. , Sauer B. W. , Leonard R. B. 
Published: December 2004

AbstractA study of the tissue compatibility of aluminum oxide implants under different stress conditions in rabbits was performed over four‐ and eight‐week implantation periods. The specific objectives were to examine endosteal bone ingrowth into aluminum oxide coneshaped plugs in amputated tibiae, while additional pellet‐shaped implants in the tibiae and femora of rabbits with amputated and nonamputated limbs were studied to determine: (1) if the degree of loading placed on the amputated limb was sufficient to promote bone activity, (2) the degree of inertness and/or toxicity of the aluminum oxide implants, and (3) a possible cause of bone spurs.The results of the radiographic, histologic and microradiographic analyses of the in vivo implants demonstrated that there was little mineralized bone ingrowth into the coneshaped aluminum oxide implants in the amputated tibiae. The study also showed that the aluminum oxide pellet implants in the tibiae and femora of the nonamputated limbs demonstrated excellent mineralized bone ingrowth into surface and internal pores. By comparing these results with the incomplete ingrowth into corresponding pellet implants in the tibiae and femora of amputated limbs, it was determined that a lack of weight bearing and damage to the musculature and vascularity following amputation were interfering with the normal bone activity and therefore bone ingrowth.Angiographs and radiographs of the amputated tibiae demonstrated that bone spurs were present and that they originated at the site of the periosteal damage. Their cause was believed to be associated with an increase in the vascularity of the adjacent tissues.
Surgical sutures and infection: A biomaterial evaluation
Authors: Edlich Richard F. , Panek Patricia H. , Rodeheaver George T. , Kurtz Leonard D. , Edgerton Milton T. 
Published: December 2004

AbstractA standardized readily reproducible experimental model has been developed to assess the relative importance of the chemical and physical configuration of sutures as determinants of early infection in contaminated wounds. The chemical structure of the suture appeared to be the most important factor in the development of surgical infection. The incidence of infection in contaminated tissues containing either polypropylene sutures or nylon sutures was lower than the infection rate of tissues subjected to any other nonabsorbable suture. Among the absorbable sutures, polyglycolic acid (PGA) sutures evoked the least inflammatory response. The infection rate of contaminated tissues containing the PGA sutures was not significantly different from the incidence of infection of tissues subjected to the least reactive nonabsorbable sutures. The physical configuration of the suture played a relatively unimportant role in the development of early infection. The infection rate of contaminated tissues containing monofilament nonabsorbable sutures did not differ significantly from the incidence of infection of tissues subjected to multifilament sutures made from the same material. Coating the multifilament suture with either silicone, wax, or Teflon did not alter the incidence of early infection in the contaminated tissue. Finally, the presence of even the least reactive suture in contaminated subdermal tissue potentiated the development of infection.
Morphologic observations of neosheath development of undifferentiated connective tissue development around artificial tendons
Authors: Salisbury Roger E. , McKeel Daniel , Pruitt Basil A. , Mason Artur D. , Palermo Nicholas , Wade Clarence W. R. 
Published: December 2004

AbstractThe management of severe flexor tendon injuries of the hand has been dramatically improved by tendon sheath reconstruction with an artificial tendon, followed by conventional tendon grafting. The purpose of this study was to investigate the nature of neosheath formation.In 25 chickens, the flexor tendons and sheaths in a toe were excised and replaced with a United States Army artificial tendon. An artificial tendon was also placed in the back, and four weeks later, tendons and surrounding tissue as well as normal tendon sheaths were excised and submitted for light, transmission electron microscopy and scanning electron microscopy.In all instances, neosheaths formed around the silastic coated artificial tendon. The neosheaths formed in the foot and back were similar to normal sheath, having the same cellular and fibrous composition. Reconstruction of the normal anatomy with an artificial tendon explains why this surgical technique gives superior results to other less physiologic procedures in patients with severe hand injuries.
The mandibular staple implant for the atrophic mandible
Authors: Small Irwin A. , Metz Herbert , Kobernick Sidney 
Published: December 2004

AbstractThe mandibular staple is an endosseous implant that will permit the attachment of a lower deture in cases of severe alveolar bone atrophy. It is placed through a submental incision and inserted into seven parallel holes drilled into the mandible. A curved bar containing seven pins is inserted in the holes and is place against the inferior border of the mandibular symphysis. The two lateral most pins project into the mouth and the five retentive pins remain completely buried in bone. Two fasteners are screwed down on the threading of the intraoral pins. Later a bridge containing Dalbo attachments is cemented to the fasteners which allow attachment to a lower denture. A series of 25 patients have been completed with 20 successful patients for survival rate of 80%. The longest case has been in for five years and the average case has been in for 3 years. Stainless steel, titanium and ceramic coated titanium has been with apparently equal success. Patient acceptance has been excellent.
The present status of endosteal oral implants
Authors: Cranin A. Norman , Dennison Thomas A. , Schnitman Paul 
Published: December 2004

AbstractThis paper presents a review of 338 metallic endosteal oral implants of six designs that had been in situ for periods of up to seven years as observed by members of the Brookdale Group. Of the 338 impervious alloplastic endosteal implants studied, none but the endodontic endosteal implant demonstrated positive long range findings. It would appear that the eventual demise of endosteal implants is predictable on a basis of time.