A method is given for calculating interfacial shear stress in porcelain-fused-to-metal restorative materials. Thermal history of the porcelain and dynamic stress relief relations are utilized to predict interfacial stress as a function of temperature. Calculations are in agreement with experimental results based on the deflection of bimaterial strips and are consistent with previously reported data.

Dental Alloys↗

PubMed1980

Creep rate of porcelain-bonding alloys as a function of temperature.

The method of beam bending has been demonstrated for measurement of creep rate as a function of temperature. Representative high gold-, gold-palladium-, and palladium-silver-based alloys have different activation energies for high temperature creep, and thus their relative "sag" behavior is expected to depend on the temperature at which the comparison is made. Near the solidus temperature, creep rates for the alloys investigated differ by an order of magnitude and become increasingly different at lower temperatures. Depending upon the presently unknown mechanisms involved in "sag" and in "margin opening" during porcelain firing, control of activation energy has varying potential for modifying creep-induced discrepancies of PFM restorations.

Chemical Phenomena↗

PubMed1979

Viscosity of dental porcelain as a function of temperature.

A method for viscosity measurement is described and representative data are given for opaque, gingival, and incisal porcelains. The significance of viscosity in annealing and in stress development due to thermal expansion mismatch is discussed. Thermal history of the porcelain is shown to be important only over a relatively small temperature interval in affecting residual stresses.

Dental Porcelain↗

PubMed1979

Minimizing corrosion of carbon steel dental instruments during autoclaving.

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Alloys↗

PubMed1978

Inhibition of corrosion during autoclave sterilization of carbon steel dental instruments.

Comparisons were made of several dip-applied corrosion inhibitors for protection of carbon steel dental instruments during autoclaving. Although none were totally effective, several provided significant corrosion inhibition. Sodium nitrite and one proprietary inhibitor were about equally effective and notably superior to the other inhibitors investigated. Because sodium nitrite is a food preservative that is relatively harmless when ingested in small quantities, whereas commercial inhibitors are of proprietary composition and unspecified toxicity, we prefer to use sodium nitrite for corrosion inhibition during autoclaving. Sodium nitritie is readily available from chemical suppliers and is generally much less expensive than most commercial inhibitors. Although the autoclave used in this investigation is typical of many used in clinical situations, minor variations in design, steam impurities, and other unknown factors might effect the results. Further research is needed to determine the corrosive effects of impurities in the steam supply, residual detergents, method of postautoclave drying, steam supply deoxygenation, pH, and possibly the use of oxygen scavengers within the autoclave.

Alloys↗

PubMedDate not supplied

Total etch--the rational dentin bonding protocol.

Phosphoric acid etching of dentin is critically reexamined in view of current adhesive resin development. Research and clinical experience both suggest that "total etch," the simultaneous etching of dentin and enamel, is a rational protocol with many modern adhesive resins.

Acid Etching, Dental↗

PubMedDate not supplied

Reliable porcelain repairs.

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Dental Porcelain↗

PubMedDate not supplied

Posterior composite technique utilizing directed polymerization shrinkage and a novel matrix.

A technique is described for novel placement of posterior composites. Two frequently encountered problems are eliminated with this technique: difficulty in achieving good interproximal contacts and composite shrinkage away from the tooth. The desirability of indirect composites is questioned in view of recent research and the technique for direct composites described.

Bicuspid↗

PubMedDate not supplied

Adhesive monomers for porcelain repair.

The purpose of this investigation was to test the bond strengths of several adhesive systems intended for intraoral resin-to-porcelain and resin-to-metal bonding. All measurements were compared with resin bonding to etched bovine enamel. Based on these data and the authors' own clinical experiences, protocols for intraoral porcelain repair are presented for fractures in porcelain only, fractures with both porcelain and metal exposed, and fractures with all metal exposure.

Dental Bonding↗