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Biomedical subjects

J M Carter

Publications and source records attributed to J M Carter.

At least 127 records · Page 7Linked to original sources
PubMed1985

Determination of residual stresses in denture base polymers using the layer removal technique.

In order to study the influence of residual stresses on dimensional accuracy and mechanical properties of denture bases, an experimental model was devised for measurement of residual stresses in acrylic denture base polymers. Rectangular bar coupons were cut from resin plates heat processed by conventional dental methods. They included samples which had been slow and fast cooled after polymerization and had been stored in dry and wet environments. Uniaxial residual stress distributions for each coupon were disclosed by removing layers of known thicknesses and measuring the ensuing deflection of the specimens. Coupons of a commercial acrylic resin were annealed and used as controls. ANOVA and Scheffe's test were used to compare experimental conditions at the 95% confidence level. Dry specimens exhibited residual surface compressive stresses from 0.43-0.83 MPa (62-120 psi). Water-stored specimens showed higher stress levels, 2.86-3.24 MPa (414-470 psi). Slow cooled pigmented acrylic coupons which were dry showed higher residual stresses compared with other dry but nonpigmented specimens. No significant differences were found between pigmented or clear coupons which contained moisture.

Acrylic Resins↗
PubMed1984

Radio frequency glow discharge and solid-phase lactoperoxidase-glucose oxidase beads as methods for etching ultra-thin plastic sections for immunoelectron microscopy.

Etching techniques to prepare ultra-thin sections for immunoelectron microscopy have incorporated a variety of reagents to expose antigenic sites. In this paper involving 2 techniques for surface etching prior to immunoelectron microscopy, radio frequency glow discharge ( RFGD ) and solid-phase lactoperoxidase-glucose oxidase beads ( Enzymobeads ) are compared to conventional peroxide etching techniques. Measuring such parameters as intensity of granule disposition and titers of antibody resulting in detectable staining. RFGD and Enzymobeads were both superior to the conventional peroxide methodology. Non-specific absorption by ferritin under the conditions utilized was not a problem with Enzymobeads or RFGD method. In addition, RFGD may be useful in situations where peroxide susceptible antigens are under study.

Adsorption↗
PubMed1984

Surface properties determine bioadhesive outcomes: methods and results.

This investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical-chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic-fibrocytic cells against the initially scrupulously cleaned, high-surface-energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre-adsorbed protein-dominated "conditioning" film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower-surface-energy materials typical of standard dental implants were "walled off" by a cell-poor, nonadhesive capsule with a fibrous interface separated from a thicker "conditioning" film by a lipid-rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.

Animals↗
PubMed1984

Fibroblastic activities post implantation of cobalt chromium alloy and pure germanium in rabbits.

Different preimplantation surface finishes were applied to surgical vitallium discs and germanium prisms implanted for 20 days within the back muscles of adult rabbits. Histopathologic analysis of the numbers of nuclei of active fibroblasts immediately adjacent to the implants was carried out. The mean apparent volume fractions (MAVF) for the subdermal implant sites were found to depend on the surface cleanliness of the implant, the cleanest or highest-surface-energy surfaces giving the highest MAVF values for active fibroblasts.

Animals↗
PubMed1983

Punch shear testing of extracted vital and endodontically treated teeth.

Plano-parallel specimens of human dentin cut from vital and endodontically treated teeth were tested by the punch shear test. Shear strength values were found to positively correlate with approximate toughness values. Statistically significant differences were found between shear strength and toughness values for vital and endodontically treated teeth, the latter showing lower values. The clinical impression that endodontically treated teeth are weaker and more brittle than vital teeth has therefore been quantitated. Anatomically different teeth or the methods used to store and cut teeth could not be consistently correlated with punch shear and toughness values. When dentin slices were constrained during punching so that bending was prevented, the precision of the results was improved and higher values were recorded.

Adult↗
PubMed1983

Microleakage of four root canal sealer cements as determined by an electrochemical technique.

Eighty-eight teeth were used to determine the sealing quality of four root canal sealer cements--Kerr, Diaket, AH-26, and ProcoSol--via the vertical condensation of warm gutta-percha technique. In addition, limited studies were carried out to determine the sealing quality of injected Hydron and thermoplasticized gutta-percha. A comparison was also made between the lateral condensation of gutta-percha and vertical condensation of warm gutta-percha when Kerr sealer was used. Teeth filled with vertical condensation of warm gutta-percha and AH-26 sealer cement showed lower leakage in one experiment but higher leakage in another. Hydron showed the highest leakage of any material. Teeth filled via vertical condensation of warm gutta-percha and Diaket showed less leakage than the other groups. A statistically significant difference was also found between lateral condensation of gutta-percha and vertical condensation of warm gutta-percha using Kerr sealer cement.

Dental Bonding↗
PubMed1982

Degradative effects of conventional steam sterilization on biomaterial surfaces.

Prior to implantation trials in animals, the effect of steam sterilization on the surface properties of metallic and coated biomaterials was studied. Pure germanium plates and cast surgical Vitallium discs and subperiosteal implants were treated to present three standard types of biomaterials surfaces prior to steam sterilization, ranging from scrupulously clean, high-energy metals to uniformly low-energy organic layers. Both before and after sterilization, the sample surfaces were characterized by a variety of nondestructive physiochemical techniques. The results indicate that steam sterilization is likely to compromise the properties of otherwise carefully prepared biomedical implants by depositing hydrophobic organic and hygroscopic salt contaminants over the implant surfaces.

Biocompatible Materials↗
PubMed1982

Case study of a diabetic dog with chronic membranous glomerulopathy treated with continuous intraperitoneal insulin infusion.

The purpose of this study was to determine the use of continuous intraperitoneal insulin infusion over an extended period (in maintaining metabolic control) and to evaluate the benefits of this treatment in reversing the kidney pathology of a chronic diabetic dog with membranous glomerulopathy. Hyperglycemia was eliminated, but reevaluations of the insulin infusion pattern were necessary. An initial kidney biopsy revealed fusion of the foot processes, thickening of the basement membrane, and subendothelial deposition. After 5 months of infusion, there was less fusion of the foot processes and a decrease in the subendothelial deposition. Urinary protein loss decreased from 17.3 g/day to 625 mg/day after 2 months of infusion. The dog gained weight, muscle wasting was reversed, and his stamina returned while on continuous insulin infusion. The reduction of a life-threatening urinary protein loss to a tolerable level and the improvement in the microscopic kidney lesions observed indicate that this treatment with insulin infusion may be beneficial in the management of long-term diabetic dogs, affected with advanced kidney lesions secondary to diabetes.

Alloxan↗
PubMed1981

Organic surface film contamination of Vitallium implants.

Conventional finishing and polishing techniques used to prepare Vitallium subperiosteal dental implant castings were found to produce low energy surfaces as measured by critical surface tension. Standard metallographic preparation gave slightly higher values. Glow discharge cleaning of both types of polished surface gave much higher critical surface tension values. This suggests the presence of an organic film after surface polishing of the implant which may later affect tissue reaction, in particular attachment, as has been noticed in related animal studies.

Adhesiveness↗
PubMed1979

Adherence of a nickel-chromium alloy and porcelain.

1. Surface oxide favors adherence. The results of this study do not support the hypothesis that chromium oxide has a deleterious effect on adherence as measured by the torsion test. 2. Gritblasting the surface before porcelain application improves adherence. Smooth uncoated specimens where oxide was removed before enameling developed insufficient amounts of oxide for bonding. 3. The particular coating agent used on this study indirectly promotes adherence, since additional oxide forms during its application. Also, it may be directly involved by its influence on the residual stress distribution in the interface porcelain. 4. The more extensive the reaction zone at the interface, the further away the fracture surface is from the interface.

Adhesiveness↗
PubMed1978

Comparison of collection techniques for quantitative urine culture in dogs.

The degree of bacterial contamination of 75 urine samples collected by voluntary voiding, catheterization, and cystocentesis was studied in 25 clinically normal dogs (14 females and 11 males) to evaluate the suitability of quantitative urine culture for diagnosis or urinary tract infection. Significant bacteriuria (greater than 100,000/ml) was not observed. Insignificant bacteriuria presumably caused by urethrogenital contaminants was detected in 44% of the urine samples collected by voluntary voiding, in 20% of the samples collected by catheterization, and in 12% of the samples collected by cystocentesis. The urine was sterile in 40% of the samples collected by voluntary voiding, in 80% of the samples collected by catheterization, and in 84% of the samples collected by cystocentesis. A bacteria count suggestive of bacteriuria (10,000--100,000/ml) was obtained in 1 sample collected by cystocentesis but was attributed to inadvertent penetration of a loop of intestine. Low bacteria counts were obtained in 4 (16%) samples collected by voluntary voiding, presumably as a result of urethrogenital and integumentary bacterial contaminants. It was concluded that urine samples properly collected from dogs by voluntary voiding, catheterization, or cystocentesis are suitable for detection of significant bacteriuria.

Animals↗
PubMed1978

A study of the corrosion of dental amalgam using the ring-disk electrode.

The rotating ring-disk electrode technique has been applied to the study of anodic dissolution of dental amalgam in a simulated saline solution. The electroactive domains of the silver, tin, and mercury couples (the main constituents of the amalgam) were determined from current-potential curves obtained at a rotating gold-disk electrode in solutions containing salts of the respective metals. Subsequently, anodic currents were applied to a rotating amalgam-disk electrode and the soluble products produced were identified using a concentric gold ring electrode, i.e., using the rotating gold-ring, amalgam-disk electrode. Species generated at the amalgam disk are transferred to the gold ring by convective diffusion. Tin ions were found to be the only soluble species generated at the amalgam disk. No evidence for dissolution of other components was found. The selective dissolution of tin from the amalgam is also consistant with potential shifts observed in reptititve current-potential curves of an amalgam disk. This study provides a direct proof for the selective dissolution of tin during corrosion of dental amalgam in an in vitro environment.

Corrosion↗