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Biomedical subjects

R P Kusy

Publications and source records attributed to R P Kusy.

At least 19 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↗
PubMed1991

Lower serum osteocalcin in ethanol-fed rats.

Serum osteocalcin was remarkably and significantly (-34 and -41% in two separate experiments; p less than 0.001) lower in rats fed an 8% (w/v) ethanol liquid diet (ELD) for 1 week than in rats fed an isocaloric control liquid diet (CLD). In a longer experiment that spanned 4 weeks, the ELD rats were given 6% ethanol on day 4, increased stepwise to 8% by day 9, and then maintained at 8% until day 28, when the experiment was terminated. Again, serum osteocalcin was much lower (-32%, p less than 0.001) in the ELD-fed rats than in CLD-fed rats. Even in rats fed only a 6% ELD for 12 days, serum osteocalcin was lower (-33%, p less than 0.001) than in controls. Also, the femora were weaker, more compliant, and more ductile in ELD-than in CLD-fed rats, findings that confirmed our earlier, related work. The fall in serum osteocalcin in ELD-fed rats is associated with a fall in femur ash weight and bone strength. There were significant correlations between serum osteocalcin and bone strength (r = 0.80; p less than 0.001) and between serum osteocalcin and bone stiffness (r = 0.83; p less than 0.001). Serum ionized calcium, like osteocalcin, was consistently lower in rats given ethanol for 1 or 4 weeks than in controls. From these experiments we conclude that excessive ethanol consumption inhibits osteoblastic activity as indicated by the reduced serum osteocalcin. The inhibition is also associated with other deleterious effects of ethanol on bone, including ash weight, bone strength, and bone stiffness.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Comparison of the frictional coefficients for selected archwire-bracket slot combinations in the dry and wet states.

Coefficients of friction were evaluated in the dry and wet (saliva) states for stainless steel, cobalt-chromium, nickel titanium, and beta-titanium wires against either stainless steel or polycrystalline alumina brackets. For both operators' experiments, an 0.010" stainless steel ligature wire pressed each archwire into the 0.018" or 0.022" bracket slot at 34 degrees C. In the dry state and regardless of slot size, the mean kinetic coefficients of friction were smallest for the all-stainless steel combinations (0.14) and largest for the beta-titanium wire combinations (0.46). The coefficients of the polycrystalline alumina combinations were generally greater than the corresponding combinations that included stainless steel brackets. In the wet state, the kinetic coefficients of the all-stainless steel combinations increased up to 0.05 over the dry state. In contrast, all beta-titanium wire combinations in the wet state decreased to 50% of the values in the dry state. The mixed reports that saliva may promote adhesive and lubricious behaviors may have some substance.

Aluminum Oxide↗
PubMed1991

Materials and appliances in orthodontics: brackets, arch wires, and friction.

The focal point for any orthodontic patient is the form and comfort of his or her appliance. To the practitioner, both can influence the function of the arch wire-bracket combination. The most critical interaction that occurs within the so-called couple is friction. When friction is high, sliding is hampered, as the efficiency and reproducibility of the appliance may be impaired. In this review, the recent advances to control friction and to modify the arch wire-bracket combination are reviewed.

Alloys↗
PubMed1990

Effects of surface roughness on the coefficients of friction in model orthodontic systems.

Orthodontists, like others (Engel, P.A. (1976) Impact Wear of Materials. Elsevier Scientific, New York.), often equate the smoothness of surfaces with the absence of friction. To investigate whether the surface roughness of opposing materials influence the coefficients of friction and ultimately the movement of teeth, arch wires were slid between contact flats to simulate orthodontic arch wire-bracket appliances. From laser specular reflectance measurements, the RMS surface roughness of these arch wires varied from 0.04 microns for stainless steel to 0.23 microns for nickel titanium. Using the same technique, the roughnesses of the contact flats varied from 0.03 microns for the 1 micron lapped stainless steel, to 0.26 microns for the as-received alumina. After each of the arch wire-contact flat couples was placed in a friction tester, fifteen normal forces were systemically applied at 34 degrees C. From plots of the static and kinetic frictional forces vs the normal forces, dry coefficients of friction was obtained that were greater than those reported in the dental literature. The all-stainless steel couples had lower kinetic coefficients (0.120-0.148) than the stainless steel-polycrystalline alumina couple (0.187). When pressed against the various flats, the beta-titanium arch wire (RMS = 0.14 microns) had the highest coefficients of friction (0.445-0.658), although the nickel titanium arch wire was the roughest (RMS = 0.23 microns). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) verified that mass transfer of the beta-titanium arch wire occurred by adhesion onto the stainless steel flats or by abrasion from the sharply faceted polycrystalline alumina flats.

Aluminum Oxide↗
PubMed1990

Dynamic mechanical properties of straight titanium alloy arch wires.

Eight straight-wire materials were studied: an orthodontic titanium-molybdenum (Ti-Mo) product, TMA; three orthodontic nickel-titanium (Ni-Ti) products, Nitinol, Titanal, and Orthonol; three prototype alloys, a martensitic, an austenitic, and a biphasic alloy; and a hybrid shape-memory-effect product, Biometal. Each wire was prepared with a length-to-cross-sectional area of at least 3600 cm-1. With an Autovibron Model DDV-II-C used in the tensile mode, each sample was scanned from -120 to +200 degrees C at 2 degrees C/min. From the data base, plots of the log storage modulus, log tan delta, and percent change in length vs. temperature were generated. Results showed that the dynamic mechanical properties of the alloys within this TI system are quite different. The Ti-Mo alloy, TMA, was invariant with temperature, having a modulus of 7.30 x 10(11) dyne/cm2 (10.6 x 10(6) psi). The three cold-worked alloys--Nitinol, Titanal, and Orthonol--appeared to be similar, having a modulus of 5.74 x 10(11) dyne/cm2 (8.32 x 10(6) psi). The biphasic shape-memory alloy displayed a phase transformation near ambient temperature; whereas the hybrid shape-memory product, Biometal, underwent a 3-5% change in length during its transformation between 95 and 125 degrees C. Among the Ni-Ti wires tested, several different types of alloys were represented by this intermetallic material.

Dental Alloys↗
PubMed1990

Coefficients of friction for arch wires in stainless steel and polycrystalline alumina bracket slots. I. The dry state.

The surface roughness and the coefficients of friction were measured for sixteen arch wire-bracket combinations. The sample included one rectangular arch wire product from each of the four principal alloy groups and one bracket product from among the stainless steel and polycrystalline alumina inventory. Although subsamples representing both the 0.018-inch and the 0.022-inch slot sizes were evaluated, no differences were observed in their rankings. When tested over a series of eight incident angles, the optical surface roughness of representative stainless steel and alumina brackets averaged 0.148 and 0.193 microns, respectively. After testing at a single angle (82 degree) and referencing a nomogram, the roughness of the stainless steel, cobalt-chromium, beta-titanium, and nickel-titanium arch wire surfaces averaged 0.053, 0.129, 0.137, and 0.247 microns, respectively. When the various arch wire-bracket couples were pressed against an 0.010-inch stainless steel ligature wire at 34 degrees C and otherwise prevailing atmospheric conditions, the coefficients of friction ranged from stainless steel (lowest) to cobalt-chromium, nickel-titanium, and beta-titanium (highest)--regardless of bracket product or slot size. These results corroborated earlier observations in which the same arch wire products were drawn between stainless steel or alumina contact flats. In the current research, the average coefficient of kinetic friction for the stainless steel couple (0.139) was less than that for the stainless steel arch wire against a polycrystalline alumina bracket (0.174).

Aluminum Oxide↗
PubMed1990

Fabrication, evaluation, and use of extracellular K+ and H+ ion-selective electrodes.

Ion-selective mini-electrodes have been widely employed to measure extracellular K+ and H+ during myocardial ischemia. However, the recent availability of this technology has not been accompanied by uniform fabrication, amplification, and calibration standards. In their fabrication, the chloride tips of Teflon-coated silver wires should be covered with a cellulose acetate-titanium dioxide sponge followed by a polyvinyl chloride (PVC)-valinomycin (K+) or PVC-tridodecylamine (H+) ion-selective membrane. Critical analysis of the nonworking electrodes using scanning electron micrographs has revealed membrane holes, membrane and sponge contamination, Teflon plaque, poor membrane-sponge-Teflon adhesion, and improperly applied or torn membrane. We have also found that signal amplification must have variable-gain filtration (0-1 Hz) with 0.5-pA input offset current and 10(12)-omega input resistance. Furthermore, in vitro calibration in 3 and 10 mM KCl (K+) or pH 8 and 6 buffer (H+) should produce a Nernstian slope +/- 5 or 10%, respectively, at 26 degrees C with a response time less than or equal to 50 ms, resistance greater than or equal to 10(12) omega, and drifts less than or equal to 1 mV/h. In vivo performance and calibration criteria (delineated for K+ only) include 1) transient response to bolus injections of KCl (0.12 mM/kg body wt) yielding peak amplitude changes of 2.5-3.0 mM, response times less than or equal to 10 s, and washout time constants less than or equal to 3 min, and 2) in vivo calibration to artificial independently confirmed systemic [K+] producing a Nernstian slope +/- 15% at 38 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The effects of scaling a titanium implant surface with metal and plastic instruments: an in vitro study.

The surface roughnesses of pure titanium implants were compared with scaling in vitro with curettes of dissimilar composition. Each of 10 transmucosal implant extensions (TIEs) was divided into three experimental surfaces and an untreated control surface. The three experimental surfaces were instrumented with either a titanium-alloy tipped curette, a curette of stainless steel, or a plastic curette. All experimental surfaces received 30 strokes with the designated curette within a 2 mm wide area. Alteration of the surfaces due to instrumentation was evaluated by a helium neon (HeNe) laser and reported as relative specular reflectance (RSR). Scanning electron microscopy (SEM) conformed the quantitative HeNe laser results. A significant decrease in mean RSR (greater roughness) was observed for surfaces treated by metal curettes compared to either untreated control surfaces (P less than 0.01) or surfaces treated by the plastic curette (P less than 0.01). No statistically significant difference was noted between untreated surfaces and those treated by the plastic curette. The titanium-alloy curette produced a significantly lower mean RSR (greater roughness) compared to those surfaces treated by the stainless steel curette (P less than 0.05). In summary, plastic instruments produced an insignificant alteration of the titanium implant surface following instrumentation, while metal instruments significantly altered the titanium surface.

Alloys↗
PubMed1989

Effects of sliding velocity on the coefficients of friction in a model orthodontic system.

Four arch wire alloy products were evaluated against 400- or 600-grit finished stainless steel contact flats at 34 degrees C under prevailing atmospheric conditions. Six relative velocities (10, 1.0, 0.1, 5 x 10(-2), 5 x 10(-3), and 5 x 10(-4) mm/min) were evaluated as many as three times each in order to simulate a range of sliding motion which approaches the mean rate of tooth motion--that of 2.3 x 10(-5) mm/min. Measurements of the static and kinetic coefficients of friction were rather invariant for the stainless steel and nickel titanium arch wire products. In contrast, a slight increase and a definite decrease of both coefficients occurred for the cobalt-chromium and the beta-titanium arch wire products, respectively. On the presumption that tooth motion routinely occurs over a wide range of sliding rates, the stainless steel couple produced the lowest and the most consistent coefficients of friction, whereas the beta-titanium wire on stainless steel flats produced the highest and the most erratic coefficients of friction. These observations should prevail whenever the film layer of saliva breaks down at, for example, the contact points of arch wire and bracket wings.

Chromium Alloys↗
PubMed1989

Influence of ethanol on stiffness, toughness, and ductility of femurs of rats.

Recently, we reported that the ingestion of alcohol in rats reduced the mechanical strength of femurs. Our results showed that, as the dose exceeded 0.012 g of ethanol per gram of body weight, a significant (p less than 0.001) loss of "strength" occurred that was independent of sex according to the relationship, Strength (N) = 140.4 - 6003 dose (g/g). In the present effort, the same flexure tests were reevaluated to include the parameters of stiffness, toughness, and ductility. These latest results confirm that the femurs of rats fed an ethanol liquid diet for 4 weeks are not only weaker but also more compliant and less energy absorbing. Although the femurs of rats fed ethanol are more ductile, the bones are more prone to fracture in fatigue and impact circumstances as well as under simple loading situations. The rat may be an appropriate model to study the mechanisms that lead to the higher incidence of fractures in the alcoholic human.

Animals↗
PubMed1988

Creep rupture of polypropylene sutures as a function of diameter, radiation dose and temperature.

The failure of polypropylene (PP) sutures was studied via creep rupture tests. Linear relationships were generated from plots of log time to break (tB) versus stress (sigma). At a constant sigma the results showed that tB was inversely proportional to the suture diameter (7-0, 6-0, 5-0 and 4-0) and to the radiation dose (0, 15, 20, 25 and 50 Mrad). Moreover, for the 6-0 suture size at a 15 Mrad dose, tB decreased with increasing temperature (26, 37, 44, 50 and 60 degrees C). For this creep rupture process the activation energy equalled 91.2 kJ/mol (21.8 kcal/mol). A mechanism for failure was presented which assumes that these sutures are bundles of oriented, semicrystalline microfibrils.

Dose-Response Relationship, Radiation↗
PubMed1988

Effects of cold disinfectants on the mechanical properties and the surface topography of nickel-titanium arch wires.

The effects of disinfectants on the mechanical properties and surface topographies were determined for 0.017 x 0.025-inch Nitinol and Titanal wires. Three disinfectants approved by the American Dental Association were tested at maximum antimicrobial concentrations: 2% acidic glutaraldehyde, chlorine dioxide, and iodophor. Bending and tensile tests were evaluated to determine whether the stiffness, strength, or range of the wires changed after disinfectant treatment. Laser spectroscopy was used to detect surface changes from corrosion or tarnish after treatment. No detrimental changes were detected in the mechanical properties or surface topography of either wire product after disinfectant treatment. Nitinol was found to be stronger and stiffer than Titanal. On average, Titanal exhibited five times more specular reflectivity than Nitinol.

Chlorine↗
PubMed1988

Effects of sterilization on the mechanical properties and the surface topography of nickel-titanium arch wires.

The effects of sterilization on the mechanical properties and the surface topography were determined on 0.017 x 0.025-inch Nitinol and Titanal arch wires. Three approved heat sterilization methods were used: dry heat, formaldehyde-alcohol vapor, and steam autoclave. Elastic moduli were obtained on 1-inch segments in 3-point bending. Laser scans of flatwise wire surfaces were conducted to detect surface alterations--whether they were caused by tarnish, corrosion, or pitting. Tensile properties were determined on 7-inch lengths: the 0.1% yield strength, the ultimate tensile strength, and the percent elongation at break. Within the confines of the present sterilization experiments, no detrimental changes were observed for either the selected mechanical properties or the surface topography. When the mean values of the two products were compared, Nitinol was less compliant but stronger than Titanal. Laser spectroscopy showed that Titanal possessed at least three times more specular reflectivity than Nitinol.

Alloys↗
PubMed1988

Surface roughness of orthodontic archwires via laser spectroscopy.

Using specular reflectance, the surface roughness of six representative orthodontic archwire products was determined. Among the four alloy groups which are commonly used in orthodontics, stainless steel appears the smoothest, followed by cobalt-chrome, beta titanium, and nickel-titanium. A clearer understanding of the parameters which contribute to sliding mechanics will be possible when these results are combined with future experiments on the coefficient of friction.

Chemical Phenomena↗