Calculation of interfacial stress in porcelain-fused-to-metal systems.

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.

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.

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.

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.

Creating tight, anatomically correct interproximal contacts.

Achievement of an excellent contact, one that provides a natural look and feel, reproducing the natural tooth contact or sometimes improving it, can be achieved in many ways. Understanding the separate issues of tightness and anatomy is crucial to achieving the desired result. In most cases, use of a contoured sectional matrix and McKean-style ring is the surest way to achieve the desired result. Unusual circumstances, such as wide preparations and malpositioned teeth, call for innovative techniques, some of which are illustrated in this article.

Removal of "black-line" margins and improving esthetics of porcelain-fused-to-metal crowns: update in technique.

A repair technique is presented for elimination of "black line" crown margins and extension of margins onto cervical surfaces. A resin bonding agent that adheres simultaneously to metal, porcelain, and dentin is utilized to expedite completion of the repair. The bonding resin is opaqued with a light-curing, filled resin and then covered with a suitable composite resin. This technique updates a previously published technique by eliminating glass-ionomer cement liners and liner etching and improves both efficiency and esthetics of the repair.

A new polymer glass utilized for modification and repair of fixed partial dentures.

A new polymer glass, Artglass, is utilized for esthetic modification of an existing porcelain-fused-to-metal fixed partial denture. The masking ability of the polymer glass is demonstrated. A procedure is described for simultaneous adhesion of the Artglass to multiple intraoral surfaces.

Adhesion monomers utilized for fixed partial denture (porcelain/metal) repair.

A technique is presented for repair of fatigue-fractured fixed partial dentures with an overlaid, bonded porcelain/metal repair. The repair techniques utilize recent advances in resin-to-metal and resin-to-porcelain adhesion. Clinical procedures are given for adhesion of repair castings to intraoral porcelain or metal surfaces. Metal surface preparation techniques depend on the chemistry of the metal and include intraoral tin plating of noble metals. Direct adhesion of composite resin luting agents is used for base metals.

Gold-acrylic resin facing replaced by intraoral bonding of a polyglass: a case report.

A gold-acrylic resin abutment for a removable partial denture was esthetically and functionally restored with a bonded Artglass facing. Surface preparations utilized were intraoral sandblasting and tin plating. An adhesive resin composite, Panavia 21, bonded the new Artglass facing to the prepared gold surface of the abutment.

Bite-formed posterior resin composite restorations, placed with a self-etching primer and a novel matrix.

Problems encountered in placement of posterior resin composite restorations have limited their clinical application. This article identifies and solves 4 of the frequently encountered problems: establishment of tight and anatomically correct contacts, refinement of occlusion, postoperative sensitivity, and time required for the procedure. A posterior resin composite is placed using a self-etching primer. A novel matrix, flowable composite, and bite-formed occlusion facilitate the clinical procedure.

Intraoral metal adhesion utilized for occlusal rehabilitation.

Recent advances in adhesive monomers and surface preparation methods allow strong resin adhesion to all intraoral metal surfaces. Resin-metal bond strengths may exceed typical resin-etched enamel bonds. Innovations in prosthetic procedures have resulted. Data for metal adhesion are reviewed and the use of intraoral metal adhesion to finalize an occlusal rehabilitation is illustrated. Included in the metal surface preparations are intraoral sandblasting and intraoral tin plating.

Building laminate veneers and fixed bridges with polymer glass technology.

A new type of material is being introduced to American dentistry. The material is a polymer glass, tested in Europe as Artglass. The material is purported to be equal to or better than porcelain for esthetic dentistry. The strength, color translucency, and color vitality allow minimal destruction of enamel for esthetics. An Artglass occlusal is less abrasive to enamel than porcelain and approximates gold. The characteristics of this material system introduces "minimal invasive dentistry" to routine dental repair and reconstruction. A case study of the senior author's reconstruction of his anterior teeth is presented.

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.