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Biomedical subjects

J E Lemons

Publications and source records attributed to J E Lemons.

At least 55 records · Page 3Linked to original sources
PubMed1989

Corrosion of dental copper, nickel, and gold alloys in artificial saliva and saline solutions.

The purpose of this investigation was to study the tarnish and corrosion of three commercial copper alloys, three experimental copper alloys, two nickel alloys, and one high-gold alloy by exposing the specimens for four weeks to artificial saliva and saline solutions. Half of the specimens were brushed, and the solutions were changed regularly. The copper-based and the beryllium-containing nickel alloys exhibited significant surface alterations after exposure to either solution. The potential of elevated release of ions to the oral cavity and to the target organs by some of the investigated alloys should be considered if dental usage of these alloys is to be extended.

Animals↗
PubMed1989

Synthetic biomaterials for spinal fusion.

Calcium hydroxylapatite (HAP), tricalcium phosphate (TCP), and Bioglass (BG) were implanted in the spines of dogs to determine their potential in augmenting and enhancing spinal fusion. HAP and TCP showed continuous bone to biomaterial interfaces of varying degrees. Trabecular bone surrounded and incorporated the particulate hydroxylapatite. Tricalcium phosphate ceramic showed little evidence of resorption. The glass particulate, BG, showed a thin, fibrous encapsulation with some adjacent bony trabeculae. Decortication and autogenous bone enhanced incorporation. This multivariant initial study showed that trends found for the biomaterials implanted independently were similar to those used in combination. No adverse tissue reactions were noted for the combination of materials.

Animals↗
PubMed1988

Tensile strength comparison of dowel plug technique to standard techniques of tendon-bone attachment.

Since tendon transplantation relies on successful fixation of the tendon transplant, a quantitative comparison of various methods of tendon attachment to bone was investigated in mongrel dogs. The methods included attaching tendon to periosteum, suturing a tendon to itself after passing through bone, stapling, and wedging a dowel plug into a hole with the tendon. Tests to failure were conducted at 0, 10, 28, and 63 days of healing. The dowel plug technique provided strong immediate fixation. After 63 days the staple, the tendon passed through bone, and the dowel plug techniques showed significant increases in strength. On tendons of similar size, the dowel plug method showed the greatest tensile strength when compared to the staple fixation. This method was a simple, reproducible technique.

Animals↗
PubMed1988

Dental implant retrieval analyses.

The evolution of surgical implant devices has been dependent upon a multidisciplinary coordination between the basic and applied biological and physical sciences. In this regard, engineering failure analyses of retrieved prostheses represent a significant contribution. Dental implant retrieval studies have provided guidance for biomaterials, designs and biomechanical function, specialized surface treatments for controlling tissue responses, and associated surgical, periodontal, and restorative regimes. The recent expansion of design concepts and restorative procedures places a new emphasis on the need for interrelated prospective laboratory, laboratory animal, and human device investigations. Retrospective retrieval analyses continue to provide guidance with regard to key concept development and the formulation of important questions and hypotheses for future investigations.

Biocompatible Materials↗
PubMed1988

Hydroxyapatite coatings.

Significant interest for orthopedic surgical applications of hydroxyapatite compounds is based on a number of reasons including the elemental chemistry of the primarily calcium and phosphate ion substances, the controllability of the crystalline and physical structures to provide a wide range of in vivo interactions, the existing literature on biocompatibility and the possibility for use as a surface coating, and the opportunity for bonding to bone and enhancing mechanical force transfer. A wide range of crystalline and structural forms can be constituted from reactions between calcium oxide and phosphorous pentoxide. These ceramics can be made in at least eight crystallographic forms with multiple opportunities to introduce other elements or structural defects. Microstructures and densities also can be varied to provide properties from relatively stable to completely biodegradable. One limitation has been the relatively low shear and fatigue strengths of the calcium phosphate-based ceramics. Although experimental for human orthopedic applications at this time, coatings are now in clinical trials using a range of substances, and active research is continuing on combinations of ceramics with higher strengths, cermets, and composites.

Biocompatible Materials↗
PubMed1986

In vitro calcification and in vivo biocompatibility of the cross-linked polypentapeptide of elastin.

The in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, which had been gamma-irradiation cross-linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n approximately equal to 240) had been used for cross-linking. The in vivo biocompatibility, biodegradability, and calcifiability of the gamma-irradiation cross-linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model.

Animals↗
PubMed1986

Properties of biomaterials.

Metallic biomaterials, including iron-, cobalt-, and titanium-based systems, have a long history of applications for surgical implant devices. The mechanical properties of these alloys (modulus, strength, and ductility) have been used to make devices to replace skeletal structures with long-term in vivo stabilities. In addition, the passive surface oxide layers have provided chemical inertness within biologic environments. Recent trends to provide porous metallic conditions for biologic ingrowth and fixation have introduced questions with regard to the relative strength and biodegradation properties. Some biomaterial strengths have been reduced to magnitudes less than 50% of the nonporous alloys, which emphasizes the criticality of design. Surface area increases of 3-10 times has emphasized biocorrosion magnitudes, the elements released to the tissues, and the biologic consequences of these products. This article provides a brief review of these issues with emphasis on mechanical-biomechanical and chemical-biochemical properties of metallic alloys.

Alloys↗
PubMed1986

Corrosion and ion transfer from porous metallic alloys to tissues.

Investigations on porous and nonporous alloys currently available for surgical implant device stabilization through tissue ingrowth have shown microstructures that are characteristic of the thermal processing history of the device and alloy with differences between the nonporous and porous devices of the same nominal chemical analysis, in vitro corrosion potentials that are similar for porous and nonporous alloys and corrosion rates that are approximately proportional to the increases in relative surface areas (X 2 to X 10); local tissue interactions at the cellular level that are specific to the type and amount of elemental constituents present at the interface; and no direct correlations between the local cellular responses (fibroblasts) and the potential for hypersensitivity and other systemically mediated responses. Evaluations of the available published literature and available information on device retrievals and analyses support the opinion that no quantitative, statistically based epidemiologic studies have yet established significant correlations between selected metallic ions and major types of tissue lesions. However, with the changes in surface area and basic surface chemistry for existing alloy systems, research on the long-term tissue responses should be emphasized. In our opinion, biomaterial surface modifications are possible, whereby the relative quantities of released ions available to the environment could be significantly reduced.

Alloys↗
PubMed1985

Compressive strength measurement and microstructure studies of hydroxyapatite cones.

Compressive strength measurement and microstructure studies of standard, diamond bur-ground, and fracture surfaces of durapatite cones were reported. The compressive strength measurements of durapatite cones were variable and strongly dependent on the test method. The fracture force ranged from 1090 to 3692 N and the calculated compressive strengths ranged from 113 (16,333 psi) to 389 mN/m2 (56,462 psi). The outer surface of durapatite cones was rough, irregular, and dense. Sharp fracture lines occurred along the longitudinal axis of the cones. Isolated porosity was seen in the fracture surface of one specimen. Grinding hydroxyapatite cones using a high-speed diamond bur with water spray produced a surface grinding feature, an irregular surface topography, and microcracks. The microcrack directions were perpendicular to the direction of the diamond bur cutting features.

Durapatite↗
PubMed1985

Evaluation of a subcutaneously implanted hydroxylapatite-avitene mixture in rabbits.

Avitene, a microfibrillar collagen hemostatic agent was mixed with hydroxylapatite and implanted subcutaneously along the inferior border of the mandible in ten rabbits. This mixture clearly enhanced surgical manipulation of the implants. Radiographic and histologic examination of the implant sites at one, three, and six months showed an acceptable host response with no apparent alteration of the favorable characteristics of hydroxylapatite implants.

Animals↗
PubMed1985

Cyclic axial loading of spinal implants.

The performance characteristics of Harrington distraction rods were evaluated and compared with paired wired L-rods when subjected to cyclic axial compression loading. Twelve fresh frozen swine spines with intact facet joints and anterior and posterior ligamentous complexes were instrumented and tested in a specially designed pneumatic testing device. Nine spines were displaced 2.54 cm over 10,000 cycles at a pressure of 10.3-13.8 kN/m2 (15-20 psi). Four spines were mounted in an Instron machine (Instron Engineering Corp., Canton, MA). Load displacement curves were determined for each spine without instrumentation, with Harrington distraction rod and with paired wired L-rods. Results of this cyclic axial compression testing showed that the Harrington distraction rod allowed 0.5 cm shortening in contrast to the L-rods that permitted 1.5 cm of axial displacement. Friction movement and metallic debris were noted between the sublaminal wires and the L-rods. The Luque Instrumented spine showed greater coronal plane displacement than the Harrington instrumented spines. Displacements in the sagittal plane were greater with the Harrington than Luque instrumented spines. Rotation changes in the sagittal plane were greater with the Harrington than Luque instrumented spines. Load displacement curves done on four spines indicated a wide range of applied load, 356 N (80 lbs) to 712 N (160 lbs) being necessary to displace the spines 2.54 cm. The clinician should be aware that the Luque system does not resist imposed axial compression loading in the axial and coronal planes as well as the Harrington distraction rod.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗