Search PubMed⌕ Search

Biomedical subjects

R P Kusy

Publications and source records attributed to R P Kusy.

9 recordsLinked to original sources
PubMed1992

Frictional coefficients of ion-implanted alumina against ion-implanted beta-titanium in the low load, low velocity, single pass regime.

The frictional coefficients were measured for four wire alloys against the flats of polycrystalline alumina cylinders using a low load, low velocity, single pass device. Ion-implantations of titanium into polycrystalline alumina flats and nitrogen into beta-titanium wires reduced the static and kinetic coefficients from 0.50 and 0.44 before implantation to 0.20 and 0.25 after implantation, respectively. These results are similar in magnitude to frictional coefficients for unimplanted, control couples of stainless steel, cobalt-chromium, and nickel titanium wires against polycrystalline alumina flats. For orthodontic applications, we conclude that more efficient and reproducible appliances can be engineered for tooth movement if ion-implantation is used to reduce the abrasion of beta-titanium by polycrystalline alumina.

Aluminum Oxide↗
PubMed1977

In situ replication techniques: I. Preliminary screening and the negative replication technique.

Fourteen commercially available elastomeric materials were investigated for their suitability as in vivo replication media. After a preliminary screening on an annotated specimen, three materials were chosen for further study. Of all materials evaluated, Xantopren Blue and Silene silicone impression materials provided the best results in vivo. This study demonstrates that a high resolution (ca 1 micron) negative replication technique may prove useful for the clinical evaluation of single-surface phenomena.

Acetates↗
PubMed1976

Influence of application technique on microstructure and strength of acrylic restorations.

An investigation was made of the influence of application techniques on the microstructure and properties of an acrylic tooth restorative. Mixtures of acrylic powder and monomer ("Sevriton Simplified") were applied by the brush technique of Nealon (J. Prosth. Dent., 2, 513, 1952) and by two bulk flow techniques. While similar porosities (about 4%) were observed, the brush technique resulted in a greater quantity of grains from the acrylic powder. Despite this, there was little difference in values of compression modulus, compressive yield stress, and diametral compressive strength. The mechanical strength of the materials studied was less than one-half that of high molecular weight poly(methyl methacrylate) (PMMA). Crack propagation studies established that the interface between the grains and matrix was not a source of weakness. However, as the matrix was crosslinked this could not be checked by solution methods of polymer characterization.

Acrylic Resins↗
PubMed1976

An extraorally activated expansion appliance for cleft palate infants.

A new lever-action expansion appliance is described which is designed specifically for use in infants with cleft lip and palate. An extraoral control knob allows for easy activation, while the important anterior cleft areas are left clear for premaxillary repositioning and clinical assessment. Activation is registered by a positive clicking sound. Rapid expansion is made possible by the design of the appliance which is retained by stainless steel pins.

Acrylic Resins↗
PubMed1975

Fractography of poly(methyl methacrylates).

For convenience in clinical manipulation, it is the practice to fabricate PMMA protheses from mixtures of powder and monomer. When the monomer is subsequently polymerized an unusual 2-phase polymeric material results in which grains of PMMA are dispersed in a matrix of the same polymer. The mechanical properties of the 2-phase materials are inferior in certain respects relative to 1-phase polymers. The purpose of the present work is to evaluate the failure of 2-phase materials by microscopical examination of their fracture surfaces. A granular microstructure was clearly distinguishable and a distinction made between materials which fail exclusively by transgranular fracture and others which additionally exhibit intergranular fracture. In order to interpret markings observed on the fracture surfaces of the complex 2-phase systems a study was made of the influence of molecular weight on the fractography of 1-phase PMMA. Molecular weight was reduced by degradation of samples by exposure to gamma-rays. The spacing of periodic rib markings on fracture surfaces was found to decrease with molecular weight and this relationship used to provide an estimate of the molecular weight of polymer in the matrix of 2-phase materials.

Dental Stress Analysis↗
PubMedDate not supplied

Characterization of cross-linked two-phase acrylic polymers.

A cross-linked network was formed in the particulate disperse phase carried over from the soluble pearls only in one material tested (L). The preparation of this material involved a slow rate of polymerization that allowed sufficient time for imbibition of the cross-linking monomer by the particles. In two of the materials (CR and S), the particulate phase was extractable and the remaining cross-linked matrix could be characterized for equilibrium swelling by volumetric measurements. Equilibrium swelling values were used to estimate densities of elastically effective chains in the network.

Acrylic Resins↗