bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of surface thermodynamics in thromboresistance of biomaterials
Authors: Neumann A. W. , Hope C. J. , Ward C. A. , Herbert M. A. , Dunn G. W. , Zingg W. 
Published: December 2004

AbstractA thermodynamic approach to the problem of platelet adsorption out of a suspension on to a smooth and homogeneous solid surface is developed. The interfacial tension values required may be estimated from contact angle data by means of an equation of state relation. According to the thermodynamic approach the functional dependence of platelet adsorption on surface tension of the solid differs according to whether the surface tension of the platelets is smaller or larger than the surface tension of the liquid in which they are suspended. The implications of this thermodynamic approach in situations where plasma proteins are present and the biomaterials surfaces may be heterogeneous and rough are discussed. Previous analyses using the critical surface tension of wetting and other surface‐related parameters are compared with the thermodynamic analysis given here.
Cast vs. wrought cobalt‐chromium surgical implant alloys
Authors: Devine T. M. , Wulff J. 
Published: December 2004

AbstractThe measured tensile and fatigue strengths of wrought and heat‐treated cobalt chromium‐molybdenum‐carbon alloys such as HS21 were found to be more than twice those of as cast alloys of the same composition. The resistance of wrought HS21 to crevice corrosion at metal‐Teflon contacts in isotonic salt solution at 37°C was found to be considerably greater than that of cast HS21, wrought HS25, wrought MP35, or 316L stainless steel which are currently used for surgical implants. The increased crevice corrosion resistance and mechanical strength of wrought HS21 as compared to as cast HS21 was attributed to greater chemical and structural homogeneity as well as to finer grain size and distribution of secondary phases. Fabrication of shaped implants from wrought HS21 is possible by techniques currently used for the fabrication of industrial parts from other wrought cobalt‐chromium base alloys.
A comparison of iliac marrow and biodegradable ceramic in periodontal defects
Authors: Levin Marvin P. , Getter Lee , Cutright Duane E. , Bhaskar S. N. 
Published: December 2004

AbstractDefects were created in the tooth‐supporting bone of six beagle dogs. Biodegradable tricalcium phosphate was compared to cancellous marrow as a treatment method. The findings indicated that ankylosis and resorption of the tooth can occur when using marrow. The ceramic‐filled defects healed slower; but the material itself was well tolerated by the tissues, initiated new bone formation, filled in the defect, and has good potential for the treatment of advanced periodontitis.
Identification of AuSn phase in Ag3Sn alloys containing gold
Authors: Malhotra M. L. , Lawless K. R. 
Published: December 2004

AbstractSubstitution of gold in part for silver in Ag3Sn alloys is found to result in two separate phases: γ (Ag3Sn particles) grains with a uniform distribution of gold within the grain and an AuSn phase in a form of ring surrounding the γ grain. The thickness of this ring increases with increasing gold concentration. The phases were identified by using the techniques of x‐ray diffraction, optical metallography, scanning electron microscopy, and x‐ray energy dispersive spectroscopy.
Thermodynamic considerations of the setting reaction in Ag3Sn amalgams
Authors: Reynolds C. L. , Barker R. E. 
Published: December 2004

AbstractThe setting reaction of Ag3Sn amalgams may be thought of as a liquid phase sintering problem in which the reactants seek to form products with the lowest thermodynamic potential. We discuss the thermodynamic and kinetic considerations of this reaction. The lowering of free energy has been given as the reason for the formation of the γ1, γ2, and β1 phases and a qualitative reaction coordinate diagram has been hypothesized. The barrier height for the formation of the β1 phase has been determined to be 137 kJ/mol.
Finite element analysis of dental structures — axisymmetric and plane stress idealizations
Authors: Selna Lawrence G. , Shillingburg Herbert T. , Kerr Peeter A. 
Published: December 2004

AbstractThe finite element method used to study stress generated in a maxillary second premolar as a result of occlusal forces. This mathematical technique has been applied extensively in structural engineering and structural mechanics. It is well suited to the analysis of stress in teeth and dental restorations because it can closely simulate the geometries, loads, and material inhomogeneities in the system being studied.
The effects of polyvalent salts on zeta potential of bone
Authors: Wilson C. N. , Miller A. D. , Nilles J. L. 
Published: December 2004

AbstractA streaming potential experiment was conducted on in vitro bone to determine the effects polyvalent salts have on bone zeta potential. Polyvalent metal salts would be introduced into local physiological electrolytes by corrosion of a metal implant or dissolution of a ceramic implant. It was hypothesized that a change in zeta potential of mineralized tissue, resulting from the introduction of polyvalent salts, could be a cause of tissue instability at the implant interface. Zeta potentials measured in bone were on the order of a few millivolts. Strongly hydrolytic metal cations such as Al+3 and Fe+3 did not have sufficient activity in buffered neutral electrolytes to alter bone zeta potential. Results suggest that less hydrolytic cations of high valence, and large polarizable anions may affect bone zeta potential.
Wettability of hydrogels I. Poly(2‐hydroxyethyl methacrylate)
Authors: Holly Frank J. , Refojo Miguel F. 
Published: December 2004

AbstractThe wettability characteristics of the contact lens material, PHEMA, with respect to water have been determined by using the sessile drop, and the captive air bubble techniques of contact angle goniometry. It is concluded that on PHEMA gels water does not spread spontaneously. Large hysteresis has been observed in the advancing and receding contact angles. This suggests that this hydrogel surface is capable of changing its free energy through reorientation of the polymer side chains and chain segments depending on the nature of the adjacent phase. The water content of the gels does not appear to have an effect on water wettability in the hydration range investigated. The minor wettability differences among the various gels studied were most likely due to differences in surface structure and segmental mobility due to inherent variations in the method of preparation. Small but consistent differences were found between the contact angles measured by the captive bubble method and those obtained by the sessile drop method, the former values being higher. These differences may not be method‐related artifacts and cannot be explained at the present time.
Biocompatible implants for the sustained zero‐order release of narcotic antagonists
Authors: Abrahams Robert A. , Ronel Samuel H. 
Published: December 2004

AbstractImplantable, sustained release drug delivery devices offer benefits not obtained through oral ingestion or injection. These include delivery at a constant therapeutic rate, thus avoiding adverse intermittent and massive dose effects, as well as reliance upon patients taking their prescribed dosages. The drawbacks to their widespread acceptance have been their inability to maintain a zero‐order release rate over an extended period of time and poor biocompatibility. Devices capable of satisfying these requirements have been developed and tested extensively for in vitro release of the narcotic antagonist cyclazocine. By using implant models prepared from Hydron, a hydrophilic polymer known to exhibit excellent tissue compatibility, we have found that the release rate could be precisely regulated by proper geometry, copolymer composition, concentration of ionogenic groups and cross‐link density. Devices in such varied forms as capusles, barrier‐film coated tablets and bulk polymerized rods have been tested in vitro for periods approaching 1 year.
Biomaterials science protocols for clinical investigations on porous alumina ceramic and vitreous carbon implants
Authors: Lemons J. E. 
Published: December 2004

AbstractA written protocol for the investigation of candidate surgical implant materials is quite important. Biomaterials science sections of clinical protocols have been developed for porous alumina ceramic and nonporous vitreous carbon biomaterials.Published data on the properties of the biomaterials were evaluated as related to bone replacement and augmentation. Where necessary, limited laboratory studies were conducted. If decisions could not be reached with respect to a given application, animal studies were initiated. The surgeons worked with biomaterials in the laboratory and the biomaterials scientist attended the experimental surgery procedures.Biomaterials Science Laboratory nondestructive investigations including stereomicroscopic and x‐ray inspections were conducted on the vitreous carbon dental implant systems. The investigations elucidated a number of unexpected features for both implant biomaterials and the overall interaction between the different disciplines resulted in a more complete protocol for the study of these biomaterials at our Medical and Dental Center.
Mechanical studies of the bone bioglass interfacial bond
Authors: Piotrowski George , Hench L. L. , Allen W. C. , Miller G. J. 
Published: December 2004

AbstractA series of squirrel monkeys received segmental femoral replacements in a study of the strength of the interface developed between the implant and bone. Implants were either made completely of bioglass‐ceramic, or 316L stainless steel with a flame‐prayed coating of bioglass. Fracture torque, energy at fracture, and shear stress at failure were compared to values obtained from a control group of pairs of tibias. Femurs containing bulk bioglassceramic implants showed about a 25% difference in strength compared to the opposite bone, while femurs containing flame‐sprayed implants exhibited extremely low structural strength. While the strength of the metal‐glass bond was very low (<500 kgf/cm2), the bonebioglass bond was found to be at least as strong as the bioglass‐ceramic, and at least 3/4 as strong as the host bone.
Mechanical properties of calcia stabilized zirconia following in vivo and in vitro aging
Authors: Kenner G. H. , Pasco W. D. , Frakes J. T. , Brown S. D. 
Published: December 2004

AbstractAging studies were done on calcia stabilized zirconia rods of 72% theoretical density to determine the effect of actual and simulated biological environments on their strength. They were aged without stress in vitro in Ringer's solution for 1, 2 and 4 weeks or in vivo in rabbits for 12 weeks. Rods aged in vitro showed mean losses in bending strength of 16, 17 and 19% respectively after 1, 2 and 4 weeks of immersion, while those aged in vivo showed a mean loss of 25%. It was concluded that the material tested would be unsatisfactory as an orthopedic replacement because of the rapid decrease in strength which occurred when exposed to actual or simulated biological media.
Soft tissue response to four dense ceramic materials and two clinically used biomaterials
Authors: Richardson W. C. , Klawitter J. J. , Sauer B. W. , Pruitt J. R. , Hulbert S. F. 
Published: December 2004

AbstractDisk‐shaped implants of spinel, alumina, mullite, zircon, a cast Co‐Cr‐Mo alloy, and ultra‐high molecular weight polyethylene (UHMWPE), were implanted in the paraspinalis muscle of 12 adult, male, white New Zealand rabbits. Prior to implantation the implants were characterized with respect to size and shape, weight and surface roughness. After periods of 1 month, 2 months, and 4 months, the rabbits were sacrificed and the tissue specimens were retrieved with the implants still intact. Histological examination of the tissues surrounding the implants along with changes in the size and shape, weight, and surface roughness of the implants were used a criteria for evaluating these materials for implant purposes.No surface degradation of any of the materials was detected using scanning electron microscopy. Fibrous tissue seemed to adhere to the UHMWPE implants more than any other material used in this study. Large amounts of fibrous tissue were also found to adhere to the cast Co‐Cr‐Mo alloy implants.The histological results indicated that within the limits of this investigation, the biocompatibility of the ceramic materials used in this study compared favorably with the clinically used Co‐Cr‐Mo alloy implants and the UHMWPE implants.
Factors influencing the creep behavior of poly(methyl methacrylate) cements
Authors: Treharne Richard W. , Brown Norman 
Published: December 2004

AbstractRoom temperature compression creep and recovery tests have been performed using samples of pure poly(methyl methacrylate) (PMMA), three commercially available poly(methyl methacrylate) cements, and several experimental cements. From these tests the influence of density, mixing procedure, particle size, methyl methacrylate‐styrene copolymer, barium sulfate, aquenous storage environments, residual monomer, molecular weight of the continuous phase, benzoyl peroxide, and N,N‐dimethyl‐paratoluidine, upon the creep behavior of PMMA cements has been determined. The important result is that lowering the porosity or residual monomer content, increasing the powder size, or adding an MMA‐styrene copolymer tends to increase the creep resistance of PMMA cement.
The use of dissimilar metals in surgery
Authors: Mears D. C. 
Published: December 2004

AbstractPreviously, the use of dissimilar metals for the construction of surgical implants has been strongly discouraged because the combination of metals was likely to provoke more rapid corrosion of one metal. With the passive alloys that are in present and future application, however, a reconsideration of the use of dissimilar metals is required. Presently available electrochemical tests allow accurate prediction of safe and unsafe combinations of metals. The use of dissimilar metals would permit selection of the alloy of appropriate mechanical properties for each part of an implant and would allow improved corrosion resistance that certain alloys can convey to other alloys with which they are in contact.
Design and fabrication of two types of artificial tendons for evaluation of surgical techniques
Authors: Wade C. W. R. , Ouellette J. E. , Hodge J. W. , Urban J. J. , Salisbury R. E. 
Published: December 2004

AbstractDouble‐loop tendons of fixed and adjustable lengths, and tendons with inner porous tapes both for anastomosis to tendon stumps have been made from readily available materials. By using stainless steel wire and polymer fibers, breakloads have been obtained that range from 20 to 100 lb and elongations have been reduced to less than 2%. Pore sizes up to 50 × 250 μ2 were achieved by using woven, knitted, and braided polyester tapes. For all tendons, Silastic was used to isolate inner fibers and to effect smooth gliding. Preliminary evaluation of these devices, after being implanted in the feet of chickens for 4 weeks, indicates that anastomotic strength of unions formed by use of loops is about 1000 g compared to more than 2000 for unions formed by tissue ingrowth.
A single unit digital flexor tendon prosthesis
Authors: King R. N. , Dunn H. K. , Bolstad K. E. 
Published: December 2004

AbstractHistorically, the surgical repair of serious injuries to the flexor tendons of the hand have met with loss than satisfactory clinical results. In an attempt to solve this problem, studies have been made on the design and testing of a Dacron polyester tendon prosthesis for complete replacement of the digital flexor tendon.The prosthesis attaches proximally at the anatomical musculotendon junction via collagen ingrowth into a fabric structure and in a similar manner distally via bone ingrowth at the anatomical insertion site. These fabrics are continuous with the tendon body of the prosthesis consisting of an inextensible braided cord which is silicone rubber coated to prevent tissue adherence in the glide zone of the tendon bed. An added benefit of the prosthesis is a simple means of length adjustment which can easily be carried out on the operating table.Studies have been performed in both dogs and chickens which indicate that sufficient tissue ingrowth occurs at both the distal and proximal anastomoses for retention of full load bearing capability in these animals and that postoperative adhesions are negligible, if present at all.Full prostheses have been implanted in dogs for periods of over 1 year and in chickens for 2 months. The chicken is the preferred animal model as a tendency for extensive scar tissue generation was shown in the dog.Both in vivo mechanical testing and histological characterizations have been made on sacrificed animals which have received the full prostheses.
Clinical considerations in the choice of materials for orthopedic internal prostheses
Authors: Scales John T. , Winter G. D. 
Published: December 2004

AbstractThe six principal clinical considerations which influence the choice of materials for total joint replacements are given.The necessity for screening tests on potentially useful materials is stressed. These should be carried out on specimens which have been exposed to the sterilizing process, which will be used in clinical practice. The materials should also be investigated after immersion in a physiological solution—bovine serum; following implantation in a large animal.Useful tests are impact testing, and wear studies using pin‐on‐disk and journal and bush specimens.In the case of total joint replacements, equipment in which joint motions and loadings can be simulated can provide valuable information. The components should also be subject to fatigue testing.There is a need to develop agreed laboratory methods for testing of materials and implants and for the long term follow up of patients.
Evaluation of a metal‐ceramic composite hip prosthesis
Authors: Hulbert S. F. , Richbourg H. L. , Klawitter J. J. , Sauer B. W. 
Published: December 2004

AbstractThis investigation attempts to apply the concept of direct sketal attachment via tissue ingrowth to the attachment of femoral head prosthess to the femur. Stainless steel (316L) canine femoral head prostheses with a ceramic coated stem were implanted into the femora of dogs and their results compared to those obtained by the impaction of stainless steel prostheses and acrylic‐stabilized prostheses. The implants were tested in vivo for time periods ranging from 2 to 13 months, after which time the animals were sacrificed and the femora excised. The femora were sectioned with the implants in place and prepared for examination by light microscopy. Bone was in closer approximation to the ceramic coated implants than to the other two types of implantations. The uncoated and acrylic‐stabilized implants were usually charaterized by the presence of a relatively thick fibrous sequestering membrane.
Fatigue fractures of the femoral component of Charnley and Charnley‐Müller type total hip prostheses
Authors: Ducheyne Paul , de Meester Paul , Aernoudt Etienne , Martens Marc , Mulier J. C. 
Published: December 2004

AbstractA survey is given of the mechanical failures of the femoral component of Charnley and Charnley‐Müller type total hip prostheses. Fractographic analysis reveals that all the prostheses have broken by metal fatigue.A review of the clinical data has been combined with a metallurgical and a mechanical study in order to assess the reasons of the mechanical failures.The following conclusions have been reached. The prosthesis should be inserted in varus position with regard to the axis of the intramedullary canal, and the prosthesis should be made of an alloy with appreciably higher yield stress and fatigue strength than the alloys of the investigated broken Charnley and Charnley‐Müller type prostheses.
Composite implants for orthopedic applications: In vivo evaluation of candidate resins
Authors: Jacobs Marc L. , Black Jonathan 
Published: December 2004

AbstractThree resins which include poly (methyl methacrylate), surgical Simplex P, and ultrahigh molecular weight polyethylene were selected to be evaluated as candidate systems for a polymer based composite for hard tissue prosthesis. Characterization of the mechanical behavior of these polymers in different environments including in vitro and in vivo storage was accomplished. As a result, conclusions were made as to which material maintained the least amount of mechanical variance as influenced by environmental effects. In vivo studies of implanted materials provided for a study of soft tissue response to each material. Conclusions were then developed as to the varying degrees of tissue reaction initiated by each material, and which resin generated the greatest tissue response with respect to the others.
Use of PMMA in expansion dental implants
Authors: Leigh Jorge A. 
Published: December 2004

AbstractThe Polymer Expansion Implant System, which is a system for the substitution of missing dental roots in natural or surgical alveolus, has been developed by the author. The polymer used is poly (methyl methacrylate) (PMMA).A material is sought that has three of the basic physical and mechanical qualities of human dentine: low modulus of elasticity, thermal and electrical passiveness, and ideal porosity. In addition it should be resistant, easily worked, biocompatible, and of low cost. Of the biomedical polymers, PMMA has these qualities, and it can be used as a substitute for dental roots.The design of bodies to be implanted as substitutes for dental roots requires: anatomical measurements of the maxilla and sockets; methods of retention by the bone tissue; and methods of insertion.The formation of lamina dura around an implanted body is a reply of the organism to the forces acting on it and a demonstration of the good interaction of the porosity of the material, the peri‐implant collagenous fibers and bone. X‐rays that demonstrate the behavior of bone to a PMMA implant are shown.Numerous expansion implants have been performed during the last 4 years with clinical and x‐ray proof of their success. Three clinical cases representing the classic applications are presented: (1) individual replacement, (2) intermediate abutment, and (3) free‐end abutment.
The epithelium contiguous with the neck of intraosseous dental implants
Authors: Johns Richard B. 
Published: December 2004

AbstractThere are three distinct regions with which a wedge shaped dental implant is in contact; the intraoral, transitional and intraosseous portions. The environment of each of these is different and will require special consideration.This investigation compares the epithelium found associated with a natural tooth to that which is found contiguous with the transitional region of an implant.The possibility of a pseudojunctional epithelium being formed in association with a glass collar processed onto the neck of a wedge shaped implant is examined. The histological appearance of a specimen in situ for 11 months shows an altered epithelial structure compared to that found adjacent to the neck of an unmodified titanium wedge shaped implant. Because the implant and glass must be mechanically separated from the tissue being examined, the value of demeneratized histological sections is limited.However, examination by a Scanning Electron Microscope of the surface of the glass after removal reveals an area of clear glass in the deeper region of the collar. Above this there is a deposit, the exact nature of which is unknown, but which might be interpreted as the contents of the gingival crevice.Although this might be interpreted as a type of epithelial attachment, other factors are necessary to ensure close gingival adaptation and limitation on epithelial downgrowth.