bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphological and biomechanical aspects of Al2O3 ceramic joint replacement. Experimental results and design considerations for human endoprostheses
Authors: Griss Peter , Heimke Günther , von Andrian‐Werburg Hanns , Krempien Burkhard , Reipa Susanne , Lauterbach Hans J. , Hartung Hans J. 
Published: December 2004

AbstractFour different acetabular replacement designs and 2 femoral head replacement designs made out of high density alumina ceramic have been tested in sheep with postoperative survival times of up to 11 months (Frialit 99: Al2O3 99.6%, MgO 0.4%).It can be concluded from these experiments that a cement free implantation technique with alumina requires a primary rigid fixation of the implant to bone, with the possibility for new bone growth along the ceramic and into grooves and macroscopic holes for further interdigitation. Three different solutions for the acetabular component can be recommended for human application.In addition, an all ceramic femoral prosthesis has been tested for bending strength in its neck region. Twenty prostheses have been fractured, all of which showed values for bending strength far higher than the physiological neck fracture level (900 kp/cm2). The present state of development of all ceramic prostheses is discussed. Up to now, the development of fibrous tissue between the bone and the ceramic implant has caused reservations with human implantation. The direct definite anchorage problem has to be resolved first.
Some factors affecting dental implant design
Authors: Privitzer E. , Widera O. , Tesk J. A. 
Published: December 2004

AbstractThe present investigation is concerned with answering some of the questions which arise when discussing the success or failure of endosteal implants on the basis of the resulting stresses caused in the surrounding bone structure. In particular, the questions examined are: 1) What affects do variations in the mechanical properties of the implant, an encapsulating membrane and the surrounding bone, have on the stress distribution? 2) Are some implant designs more affected than others, as indicated through variation of bone properties? and 3) What is the affect of an encapsulating membrane and how does a change in its thickness affect the stress distribution? A similar study was conducted on a simulated tooth, so that a comparison may be made between implant and tooth related stress distributions. The method of analysis used to obtain answers to these questions is the finite element method.Results of the investigation show that for a fixed implant geometry, a change in implant properties causes only minor changes in the bone stress distribution. A change in the membrane and bone properties, however, has a greater affect on the resulting stress distribution. It is also shown that the presence of a protective membrane has a beneficial affect on the stress distribution in the surrounding bone structure and that an optimum thickness can be estimated. Finally, the results show that some implant designs create a situation which results in stronger dependence of stress upon the properties of the surrounding bone.
Alumina and zirconia coated vitallium oral endosteal implants in beagles
Authors: Cranin A. Norman , Schnitman Paul A. , Rabkin Michael , Dennison Thomas , Onesto E. J. 
Published: December 2004

AbstractThe purpose of this study was to assess the addition of a ceramic coating upon a Vitallium implant to increase the implant's biologic acceptability in the oral environment. The mandibular premolar teeth in 9 adult beagle dogs were removed bilaterally and these areas allowed to heal for 6 weeks. Ceramic coating with either Al2O3 or ZrO2 was carried out by flame spray deposition upon Vitallium anchor implants (9 of each), and the implants placed into the 18 healed premolar areas. Clinical and radiographic evaluation was conducted by 2 independent investigators over a 32 week period. Implants which exhibited mobility greater than II on a scale of 0 to III, at intervals of one‐half, were judged unsatisfactory. After 19 weeks, all 9 Al2O3 coated implants and 5 ZrO2 coated implants were rated unsatisfactory. After 32 weeks, 4 ZrO3 coated implants were in situ with 0 or I mobility. Radiographically the width of the peri‐implant space increased in direct proportion to both time and mobility. Histologic sections demonstrated encapsulating dense fibrous connective tissue which was oriented parallel to both ZrO2 and Al2O3 implants. Results suggest the zirconia used is a superior ceramic coating to the alumina. Neither seemed to increase biologic acceptability over uncoated Vitallium implants.
Development of needles and sutures for microsurgery
Authors: Roberts W. N. 
Published: December 2004

AbstractAt present, the smallest needle commonly available is about 130 μm in diameter in combination with a suture of about 25 μm in diameter. Marked reductions in size, particularly of the needle, are advantageous for microvascular surgery.A needle of about 70 μm in diameter, welded to a suture of about 18 μm diameter, has been developed. In initial tests, it has performed satisfactorily in the repair of the carotid artery of the white rat. It is shown that the basic properties of materials severely limit further reductions in the size of needles and sutures.
Cell adhesion to polymeric materials: Implications with respect to biocompatibility
Authors: Ratner Buddy D. , Horbett Thomas , Hoffman Allan S. , Hauschka Stephen D. 
Published: December 2004

AbstractThe adhesion of radio‐labeled chick embryo muscle cells to the surfaces of radiation grafted hydrogels and other polymeric materials was measured in vitro. The degree of adhesion was determined by measuring the percentage of cells which remained adherent to the surfaces after 180 min of contact time (plating efficiency). Plating efficiency was found to vary between 2 and 94% depending on the nature of the surface. Preadsorption of albumin, γ‐globulin or fibrinogen markedly affected subsequent adhesion of cells. Radiation grafted poly(2‐hydroxyethyl methacrylate) and poly(N‐vinyl‐2‐pyrrolidone) hydrogels on silicone rubber demonstrated exceptionally low adhesiveness in this assay. The potential for using this cell adhesion assay as a general screening test for biomaterials is discussed.
A failed Vitallium/stainless steel total hip replacement: A case report with histological and metallurgical examination
Authors: Gruen T. A. , Amstutz H. C. 
Published: December 2004

AbstractA case of a failed total hip replacement consisting of a Vitallium hip socket and a stainless steel femoral head prosthesis is presented. The mixed‐metal combination and inadequate design resulted in severe abrasive wear and fretting corrosion of the bearing surface, and the accumulation of stainless steel wear debris and corrosion products in the periarticular tissues was extensive.The tissue response was primarily fibrotic scarring with severe histiocytic and mild foreign body giant cell reaction. Despite the massive accumulation of wear debris and corrosion products, however, there was minimal chronic inflammation and no acute inflammation.
Determination of fluorocarbon in blood
Authors: Stein T. P. , Robbins Winston K. , Brooks Helene B. , Wallace Herbert W. 
Published: December 2004

AbstractBecause fluorocarbons can dissolve relatively large quantities of oxygen and carbon dioxide, there is considerable interest in utilizing them to develop new methods of extracorporael circulation, artificial red blood cells, and liquid breathing techniques. A method for the assay of fluorocarbon in blood is presented. The fluorocarbon is extracted from the blood with toluene, and fluoride is released from the fluorocarbon in the toluene extract by reaction with sodium biphenyl. The inorganic fluoride is then extracted with aqueous sodium acetate, the pH of the extract is adjusted, and the activity of the fluoride ion is read with a fluoride‐specific ion electrode. The assay was effective for fluorocarbon concentrations in the range 1 to 30 ppm.
Platelet adhesion and contact activation time tests on HEMA coated cellulose acetate membranes
Authors: Muzykewicz K. J. , Crowell E. B. , Hart A. P. , Schults M. , Hill C. G. , Cooper S. L. 
Published: December 2004

AbstractSurface modification of cellulose acetate dialysis membranes was carried out by 60Co radiation induced graft copolymerization of the hydrogel, hydroxyethyl methacrylate (HEMA). The degree of grafting was controlled by varying the HEMA monomer concentration in the grafting solution and the radiation dose. A continuous flow platelet adhesion test was designed which allows testing under conditions more closely approximating hemodialysis than other small scale in vitro tests. Platelet adhesion on treated membranes fell substantially with increasing surface HEMA concentration. The presence of HEMA on the membrane surface did not affect the membrane activated clotting times significantly.
Correlation of in vivo collagen degradation rate with in vitro measurements
Authors: Yannas I. V. , Burke J. F. , Huang C. , Gordon P. L. 
Published: December 2004

AbstractThe rate of in vitro enzymatic degradation of various materials based on collagen has been determined by a novel mechanochemical method, and has been compared with the extent of degradation resulting from subcutaneous implantation in guinea pigs. In vitro data correlate well with in vivo data. It is suggested that the simple in vitro method described is an effective means of screening a large number of materials based on collagen for their ability to resist degradation during implantation in animals.
Reaction associated with a silicone rubber gel: An experimental study
Authors: Rigdon R. H. , Dricks Alfred 
Published: December 2004

AbstractA blend of Silastic 382 (Room Temperature Vulcanizing, RTV) Medical Grade silicone oil and a catalyst was prepared in vitro, in both the catalyzed and noncatalyzed state, and injected subcutaneously in mice, rats, and rabbits. When properly blended, this catalyzed material, referred to as “silicone gel,” formed a soft rubbery mass that remained at the site of injection. Properly catalyzed silicone rubber gel produces no macroscopic inflammatory reaction, attracts few polymorphonuclear leucocytes, and after 5–6 days a thin fibrous capsule begins to form around the gel. No degeneration of the silicone gel was observed during the 62 days of this experiment. Additional rats with this silicone gel have been under observation for 8 months and clinically have shown no changes in the local mass of silicone. If the catalyst is partly oxidized when added to the silicone fluid, the degree of gelling is much less. A local mass usually forms at the site of injection with some of the fluid diffusing into the tissue, forming minute cysts. The inflammatory reaction is characterized by polymorphonuclear leucocytes, associated with many macrophages and giant cells phagocytizing oil droplets and particles of the diatomaceous earth. The pathogenesis of the inflammatory reaction is discussed, referring to the ionic change and the emigration of polymorphonuclear leucocytes to particles of plastics embedded in tissue.
Long‐term experience with poly(glycol monomethacrylate) gel in plastic operations of the nose
Authors: Voldřrich Z. , Tománek Z. , Vacík J. , Kopečcek J. 
Published: December 2004

AbstractBetween 1964 and 1970 the authors implanted Hydron gel in 62 patients with nose malformations. The cosmetic defects most freqently operated on were the saddle, and scoliosis of the nasal dorsum. By the end of 1973,39 of the total number of cases were checked again. In two cases, the gel had to be removed shortly after the operation because of local inflammatory changes. No signs of hypersensitivity could be detected. Calcifications were detected by x‐ray examination in 54.2% of the cases. Thirty‐four of the patients subjected to the checkup were satisfied with the results of their operations. The authors considered the results to be very good in 16 cases, and unsatisfactory in 6 cases. Calcifications detected by x‐ray examination did not affect the final cosmetic effect.None of the examined patients had any complaints in connection with longterm application of the gel. Hydron gel seems to be a suitable implant material in plastic operations of the nose.
Reconstruction of the canine Achilles and patellar tendons using Dacron mesh silicone prosthesis. I. Clinical and biocompatibility evaluation
Authors: Amstutz H. C. , Coulson W. F. , David E. 
Published: December 2004

AbstractSurgical replacement of the Achilles and patellar tendons using Dacron mesh silicone prostheses was performed in 15 mature beagle dogs. This part of the study includes clinical evaluation, gross inspection at autopsy of regrown tendons, and histological determination of biocompatibility of prosthetic implants.Functional continuity and integrity of prosthetic patellar tendons have been established by evaluating the biologic–prosthetic interface and the mechanical properties of regrown tendon tissue around and through the Dacron silicone replacements. Results of prosthetic Achilles tendons were less satisfactory because of difficulties in suturing to a muscle and its fascia. Although the prosthetic tendon did not regrow through the tube, it provided a structure for regrowth around it. The regrown tendons became nearly ten times the normal crosssectional area after three to four months and decreased to two to three times after 13 months.Histological studies indicate that in the absence of infection, the Dacron mesh silicone tendon was well tolerated for periods up to 13 months. Overall results are encouraging and warrant further investigation although the regenerative capacity of human patellar and Achilles tendons is unknown.
Hair sampling for chromium content following Charnley hip arthroplasty
Authors: Owen R. , Meachim G. , Williams D. F. 
Published: December 2004

AbstractThe chromium content of hair has been studied by neutron activation analysis of samples from 62 patients following a Charnley unilateral or bilateral hip arthroplasty by an artificial joint of stainless steel against polyethylene, inserted three to five years previously. The patients lived in the North Wales area of the British Isles. Hair chromium content was also studied in 51 control subjects of similar age to that of the patients, from the same geographical area and often from the patients' own households.Chromium content was recorded as parts per million (ppm) of hair weighed and analyzed in the state received, without preliminary ashing or chemical “washing” of the samples in the laboratory. Fifty of the 51 control subjects showed less than 2 ppm chromium in hair; one showed 2–5 ppm; none showed more than 5 ppm. Fifty‐nine of the 62 patients showed less than 2 ppm chromium in hair; three showed 2–5 ppm; none showed more than 5 ppm.Attention is drawn to certain practical aspects when collecting hair samples for chromium analysis. The use and validity of hair sampling as one method of screening for systemic chromium accumulation following implant surgery is discussed. The method may be a useful adjunct to monitoring of chromium levels in blood samples. In this preliminary study, hair sampling has given no evidence of any major risk of systemic chromium accumulation in patients using a Charnley arthroplasty for periods of up to five years; no conclusion can be made concerning periods longer than this. The findings do not exclude systemic reactions of the hypersensitivity type, since this type of reaction could develop to only small amounts of chromium.
Effects of solvent casting copolymer materials as related to mechanical properties
Authors: Bagrodia Shriram , Wilkes Garth L. 
Published: December 2004

AbstractUsing a well characterized series of styrene butadiene triblock copolymers a systematic study was carried out to determine the influence of casting solvent, used for film preparation, on the final mechanical properties. The results clearly indicate that in the range of styrene contents of 30–40 mol %, the modulus behavior is greatly affected as the solubility parameter of the casting solvent, δ, is varied. Specifically, the modulus increases as δ increases to the value of polystyrene. At lower or higher styrene content, the properties are influenced but to a much lesser degree. Other mechanical properties measured were yield stress and breaking stress. The ramifications of these data are discussed in light of preparing prosthetic material via solvent casting.
The biostability of silicone rubbers, a polyamide, and a polyester
Authors: Roggendorf E. 
Published: December 2004

AbstractA biostability test program was designed after evaluation of the relevant literature on in vivo aging phenomena in plastics and elastomers. The program comprised macroscopic, microscopic, mechanical, and physicochemical investigations. Five silicone rubbers, one polyester, and one polyamid were tested as to their aging behavior and their suitability for long‐term implantation in the human body was assessed. In order to be able to state the applicability of materials used for endotheses, the various aging phenomena had to be divided into three groups, viz. unspecific, relative, and absolute indications of aging or unserviceability.Changes due to aging were found in all types of implanted plastics and elastomers. Thus, the formation of layers on inlay surfaces occurred regularly and the same would apply to changes in mechanical characteristics during the tensile test. Aging processes resulting in total unserviceability were fragmentation and crazing in the polyester and polyamide sheetings. Other aging phenomena which will easily fit into the classification given above are changes in electrical test values, protein, and lipid depositions without stronger absorptive adhesion, crystallizations on the surface of silicone vulcanizates, and chemical changes in the polyester and polyamide sheetings.Following the assessment of the materials used for endotheses, the test methods used have been evaluated with regard to their suitability for the testing of biostability.
Transient diffusion effects in the study of early platelet adhesion
Authors: Butruille Y. A. , Savitz S. R. , Leonard E. F. , Litwak R. S. 
Published: December 2004

AbstractIn the study of interactions of blood with artificial surfaces, it is common practice to wet these surfaces with a saline solution before exposing them to blood. The effect of this procedure on subsequent adhesion of blood platelets has been investigated both theoretically and experimentally, with a spinning disc apparatus. A large part of the observed delay in the initiation of platelet adhesion when using this apparatus is attributed to the time involved in displacing the prewetting fluid and bringing platelets near the surface. This observation is relevant to speculations of other researchers about the time course of adhesion‐related reactions at the surface‐proper. Other theoretical solutions are developed for the transient Leveque problem, which relates to a uniform shear‐flow near a surface, and for a stagnation point apparatus. These solutions are compared with delay effects noticed in experimental data published by others.
The influence of surface chemistry on implant interface histology: A theoretical basis for implant materials selection
Authors: Clark A. E. , Hench L. L. , Paschall H. A. 
Published: December 2004

AbstractA theory is proposed stating that an ideal implant material must have a dynamic surface chemistry that induces histological changes at the implant interface which would normally occur if the implant were not present. Evidence for the validity of this theory is provided with a series of bone‐implant studies which result in stable interfacial osteogenesis under specific implant surface chemistry conditions. Insufficient or excess surface ion concentrations produce negative osteogenesis and fixation results. Implantation of osteogenic implants in soft tissues also produces undesirable histological responses as proposed in the theory. A variety of surface chemical analyses of the implant are reviewed which provide a scientific basis for the implant surface theory.
Biocompatibility of materials for total joint replacement
Authors: Escalas Felix , Galante Jorge , Rostoker William , Coogan Philip 
Published: December 2004

AbstractThe clinical use of total joint prostheses demands absolute biocompatibility of the materials employed.The purpose of this experiment was the bioassay of some materials considered as possible candidates for use in total joint prostheses as load‐bearing members or as wear‐resistant surfaces.Some materials already in use were also tested. 316L stainless steel was used as a control. The materials were implanted as a standardized rod and in particulate form.An average of 12 samples per material were implanted in soft tissue for six months and a total of 145 rabbits were used in this study. Twenty‐five materials including metals, polymers, and ceramics were tested in solid and powdered form.A semiquantitative evaluation of local tissue reaction and a study of organs was performed.Polymers and metallic materials showed in general a mild tissue reaction. Ceramics, which some authors describe as the best tolerated materials, elicited variable tissue responses. Some of these (glass–ceramics) presented very poor tissue tolerance. The least reactive, titanium oxide, titanium aluminate, and aluminum oxide, presented a degree of tissue reaction comparable to that of corrosion resistant metals, but not superior to them. Moderate reactivity was the general rule for particulate materials except for the Pyroceram glass–ceramics, polyimides, and Teflon. Ultrahigh molecular weight polyethylene in particulate form elicited a rather cellular tissue response, a fact to be considered when projecting long‐term results in total joint arthroplasty.No pathological changes compatible with systemic toxicity by materials tested were observed in the study of the organs.
Tendon grafting with glutaraldehyde fixed material
Authors: McMaster William C. , Kouzelos Jack , Liddle Shardon , Waugh Theodore R. 
Published: December 2004

AbstractAn evaluation of 0.2% buffered glutaraldehyde fixed tendon as a potential tendon replacement prosthesis was evaluated in rabbit and chicken models. In vivo implantations were done to determine compatability, function, and strenght of grafts, Autogenous fresh grafts were used as controls in the strenght in tension compares favorably to a fresh autogenous control. These preliminary evaluations indicate a useful potential for this fixed biomaterial as a tendon prosthesis.