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Biomedical subjects

H J Mueller

Publications and source records attributed to H J Mueller.

At least 37 records · Page 2Linked to original sources
PubMed1986

Noise level evaluation of dental handpieces.

We evaluated the noise level of fourteen air-driven handpieces, six low speed (less than 20,000 rev/min) and eight high speed (greater than 160,000 rev/min), with respect to a three-directional co-ordinate system and distances of 6, 12 and 18 in. in each chosen direction. A two-way analysis of variance of the noise level between handpieces and positions indicates that large significant differences exist amongst handpieces and in different positions, and that interaction is just barely significant. The ranking and least significant differences for the mean of all handpieces v. position and for the mean of all positions v. handpiece were compared with the results for the ranking and significances from the one-way ANOVAS for each handpiece v. position and for each position v. handpiece. A trend exists with some of the handpieces of straight design (all low speed) for increased noise levels in a direction perpendicular to the handpieces and decreased levels in a direction parallel to the handpieces. For handpieces of angled design (all high speed) both directions parallel and perpendicular (the perpendicular to the longitudinal turbine axis) to the rotor axis indicate increased noise levels. The parallel direction includes the exiting air from the exhaust port. The perpendicular direction can be indicative of an aerodynamic factor associated with the established air flow patterns. The extremes in noise level were 56.8 dBA for a low-speed handpiece of straight design at the 18 in. distance in a direction parallel to the handpiece, and 87.3 dBA for a high speed handpiece at the 6 in. distance in a perpendicular direction.

Dental High-Speed Equipment↗
PubMed1986

Particle and pore size distributions of investments.

The particle-size distributions of investment powders and the pore-size distributions of set-fired investments were investigated by electrozone size analysis, and by mercury intrusion scanning porosimetry, respectively, for a number of different investments, representing all three types available, namely: the gypsum-, phosphate- and silicate-bonded. The pore volume (V), the pore surface area (S), and their first derivatives with respect to radius, r, dV/dr and dS/dr, were obtained with pressures up to 414 MPa corresponding to spherical pores of 0.0018 micron radius if the Washburn equation is to apply. Results distinguished pores with a range of different sizes. Besides the porosity due to the matrix binder, porosity was also attributable to the refractory components. This latter type of porosity occurred with pore radii below about 0.03 micron, whereas matrix porosity occurred above this pore size. Matrix porosity for the phosphate materials was smallest at about 0.03 to 0.5 micron in radius, followed by the gypsum materials at about 0.3 to 0.6 micron, and by the silicate materials at about 1 to 10 micron. The particle-size distribution of the investment powders may affect both types of porosities, whereas the setting chemistries of the particular investment types may affect matrix porosity, by the generation of gaseous by-products. No major distinctions in pore size and distributions occurred between air-set and hygroscopic-set materials. This study emphasizes that at present, knowledge of the total pore volume only is inadequate for characterizing porosity distribution and hence investment permeability.

Calcium Sulfate↗
PubMed1985

Binding of corroded ions to human saliva.

Employing equilibrium dialysis, the binding abilities of Cu, Al, Co and Cr ions from corroded Cu-Al and Co-Cr dental casting alloys towards human saliva and two of its gel chromatographic fractions were determined. Results indicate that both Cu and Co bind to human saliva i.e. 0.045 and 0.027 mg/mg protein, respectively. Besides possessing the largest binding ability, Cu also possessed the largest binding capacity. The saturation of Cu binding was not reached up to the limit of 0.35 mg protein/ml employed in the tests, while Co reached full saturation at about 0.2 mg protein/ml. Chromium showed absolutely no binding to human saliva while Al ions did not pass through the dialysis membranes. Compared to the binding with solutions that were synthetically made up to contain added salivary-type proteins, it is shown that the binding to human saliva is about 1 order of magnitude larger, at least for Cu ions.

Aluminum↗
PubMed1984

The effect of exposure conditions upon the release of soluble copper and tin from dental amalgams.

The concentrations of soluble copper and tin which were generated by the corrosion of a number of different amalgams in both an artificial saliva and Ringer's solution are reported. Besides variations in solution composition, the effects of solution agitation and abrasive particle wear upon the release of soluble species are studied. Immersion only, moderate solution agitation, vigorous solution agitation with abrasive particle wear, and accelerated corrosion by both constant currents and cyclic voltammetry are included. The results indicate that an artificial saliva but not Ringer's solution is capable of generating high levels of soluble tin. With artificial saliva, agitation increases the amalgam weight losses and increases soluble copper and tin concentrations, whereas agitation with Ringer's solution decreases sample weight losses and decreases levels of soluble copper and tin. This latter effect is believed to be due to the increased oxygen supply to the amalgam surfaces with agitation and the greater ability for producing protective passivating films of the basic hydroxide and copper chlorides in solutions of higher chloride ion concentrations e.g. Ringer's solution. Abrasive particle wear, including pumice, alumina, glass beads, and silica gel had varied effects upon the release of soluble species. Depending upon the amalgam, the solution, and the abrasive combination, either larger increases in copper or in tin occurred or reduced concentrations.

Copper↗
PubMed1984

Dynamic loading of dental amalgam and effects upon electrochemistry and microstructure.

The stress vs. cycles (S-N) behavior for four amalgams is reported. At 10 cycles/min and for 37 degrees C air and artificial saliva environments, linear regression lines fit the data with high correlations between 10(2) and 10(4) cycles. Significance at 50% exists between the environments and with saliva decreasing failure resistance. The open circuit potential (OCP), the OCP-time transients at constant anodic currents, and the cyclic voltammetry all exhibit changes with loading. With static loading the OCP decreases, while with dynamic loading the OCP exhibits a sinusoidal pattern and a pattern with two maxima and two minima after the loading has progressed and which continues up until failure. The maximum anodic current in voltammetry increases with continual potential cycling (or load cycling), while decreases when performed without loading. The application of anodic currents to the amalgams has, however, not significantly reduced the number of cycles to failure, nor has the application of cathodic currents increased the number of cycles. Rearrangement and coalesence of voids takes place with loading and with microcracking forming preferentially between them. Crack propagation occurs predominantly within the gamma-1 matrix.

Air↗
PubMed1983

The binding of corroded metallic ions to salivary-type proteins.

Employing equilibrium dialysis, the binding ability of nickel, copper, and chromium from the corrosion of Biobond, Sybraloy, and Vitallium dental alloys in an inorganic saliva to glycoprotein, mucin, amylase, and lysozyme is reported. Binding was highest with copper to glycoprotein at 5.0 M Cu/M protein, followed by nickel at 1.2 M Ni/M protein, and by chromium at 0 M Cr/M protein. Tin products did not succumb to dialysis. The binding to all types of proteins exhibited molar ratios of about equal magnitudes except in lysozyme where binding was very low, most likely due to its high isoelectric point. Protein--protein interactions for amylase were higher, which hindered the nickel binding at lower protein concentrations. Peaks in glycoprotein binding vs pH behaviour occurred for copper at pH = 6 and for nickel at pH = 7. For glycoprotein and mucin, binding is taken to occur via the sialic acid carboxylate groups and for amylase via the imidazole groups of the histidine residues. It is thought that in order for copper to bind with the same number of sites as does occur with nickel, ligands of the form CuCl-CuCl2 are generated. The size of hexahydrate ligands of chromium are large which may not permit attachment onto binding sites.

Cations↗
PubMed1983

Silver solders exposed to cleansers.

Substantiation of the adverse replies received by the Council regarding the increased corrosion of stainless steel-silver solder couples exposed to Efferdent's New Improved 36% stronger formulation is not made. Distinctions are, however, observed between the modes of corrosion occurring in the New Improved Efferdent and in the original Efferdent formulation. Corrosion in the New Improved Efferdent occurs via the formation of soluble zinc and copper chlorides that leave the selectively attacked microstructure visible, and in Efferdent nonprotective corrosion product deposition consisting of hydroxides and sulfides occurs that obscures the underlying substrate solder microstructure. The apparent increase in corrosion with New Improved Efferdent may be caused by the incorrect association between macroscopic surface appearance change and the amount of corrosion damage.

Corrosion↗
PubMed1982

Some considerations regarding the degradational interactions between mouth rinses and silver-soldered joints.

For immersion tests with mouth rinses of Lavoris, Green Mint, and Cepacol, silver solders and silver-soldered stainless steel joints exhibited corrosive degradational reactions. Exposures to Lavoris resulted in the severest surface attack as followed by optical microscopy, scanning electron microscopy, and energy-dispersive x-ray microanalysis. This was confirmed by measurements of electrochemical potential and polarization. The cyclic voltammograms in Lavoris indicated a highly active corrosion potential of -0.94 v. sce, while potentials in Mint and Cepacol were only about -0.25 v. This activity is attributed to the presence of zinc chloride as the active agent in Lavoris, as well as the high zinc content (up to about 20 percent) and even higher zinc concentrations contained in copper-zinc microstructural phases of the silver solders and the ease for dezincification corrosive attack. Large increases in current above about -0.2 v. are observed with all rinse solutions as well as a prepared saliva substitute solution. The importance of toxicologic considerations of the agents released from silver solders and the interactions of corrosion with stress as factors in causing delayed failures of soldered joints are discussed. The presently available commercial solders without cadmium and zinc contents, but with higher fusion temperatures and decreased flow characteristics, are recommended for dental applications to increase the resistance to corrosion.

Chemical Phenomena↗
PubMed1980

Characterization of some denture cleansers.

1. From comparison of calculated reaction times for homogeneous H2O2 aqueous decomposition containing alkali to the measured rates of H2O2 dissociation in the cleanser systems, it is apparent that the cleansers are further catalyzed either heterogeneously and/or homogeneously. Long-term O2 measurements indicate cleansers with O2 concentrations similar in magnitude to concentrations observed at early times. First-order reaction times, as well as the high solubility of O2 in water, can explain these high long-term O2 concentrations. 2. The process of catalyzing the H2O2 to O2 varies with cleanser product. Cleansers like Efferdent, Polident, and Kleenite exhibit high H2O2 concentration changes and high O2, suggesting the decomposition of H2O2 to O2. DOC exhibits high H2O2 concentration changes and low O2, suggesting the H2O2 decomposition via the perhydroxyl ion, HO2-. 3. The CO2-H2O system contributes to the aqueous chemistry of the slightly basic cleansers of Efferdent and Polident. Measured CO2 concentrations of these cleansers were high in comparison to the more basic cleansers of Kleenite and DOC. 4. Differentiation of the cleansers were made in terms of the Cl- concentration. Kleenite exhibited Cl- concentrations at least 10(2) times the concentrations found in Efferdent and Polident.

Boron↗
PubMed1980

Silver-tin alloys and amalgams: electrochemical considerations.

The corrosion potential and anodic polarization profiles of a representative number of silver-tin alloys and their corresponding amalgams in a physiological solution were determined and compared to their microstructures. For the alloys with tin-content greater than 27%(wt) and for all amalgams, the corrosion process is related to the attack of free tin for the alloys and to the gamma-2 tin for the amalgams. The gamma-2 concentration in the amalgams increases with an increase in tin-content. For alloys with tin-content less than 27%, the corrosion process is even more restricted than for the process observed with pure silver. From a developed theory based upon the potential-time and polarization results, association of the O2 reduction process on a SnO cathodic film to an intermediate specie of H2O2 is made. The rate of H2O2 decomposition on a SnO surface in a four electron process is thought to control the O2 reduction overvoltage. The O2 reduction overvoltage decreases with increases in the silver-content of the amalgam, particularily seen with the 8 and 12% tin compositions. Due to the polarization induced corrosion process, a phase with high silver and high mercury concentrations was observed over the unreacted particles.

Calcium Chloride↗