Crowns and bridges

In dentistry, palladium alloys are widely used as alternatives to base metal alloys in the manufacture of crowns and bridges as weU as the replacement of lost or damaged teeth (see Dental materials). Such alloys contain over 80% palladium, and hence offer significant cost benefits over alloys containing a high proportion of gold. 

Zinc oxide—eugenol impression pastes are used primarily as corrective washes over compound impressions, as veneer impressions, as temporary liners or stabilizers in base-plates and dentures, and as bite-registration pastes for recording occlusal relationships in inlay, crown, and bridge techniques. 

Inl y Casting Waxes. The three types of inlay casting waxes, ie, types A, B, and C, are used to produce wax patterns for the lost wax casting process in the production of cast gold inlays, crowns, and bridges. Some inlay wax is also used to produce patterns for acryflc restorations. 

Platinum has many uses in dentistry. Pure platinum foil serves as the matrix in the constmction of fused-porcelain restorations. Platinum foil may be laminated with gold foil for cold-welded foil restorations. Platinum wire has found use as retention posts and pins in crown and bridge restorations. Heating elements and thermocouples in high-fusing porcelain furnaces are usually made of platinum or its alloys (see Platinum-GROUP metals). 

Table 10. Composition of Base-Metal Alloys for Crowns and Bridges, %...

Casting of Ti alloys for crowns and bridges is done in investment molds that have been allowed to cool almost to room temperatures after firing. The castings are cleaned in electrolytic solutions or in special chemical polishing solutions that impart a bright smooth surface finish to the casting... 

Uses. Dental solders and fluxes are used to join orthodontic wires, fasten attachments to partial dentures, repair castings units, and join crown and bridge units either before or after the appHcation of porcelain. They may also be used to repair fixed and removable dental appHances. 

Resins are also used for permanent tooth-colored veneers on fixed prostheses, ie, crown and bridges. Compositions for this application include acryflcs, vinyl—acryflcs, and dimethacrylates, as well as silica- or quartz-microfilled composites. The resins are placed on the metallic substrates of the prostheses and cured by heat or light. These resins are inexpensive, easy to fabricate, and can be matched to the color of tooth stmcture. Acrylic facings do not chemically adhere to the metals and are retained only by curing the resin into mechanical undercuts designed into the metal substrate. They have relatively low mechanical strength and color stability, and poor abrasion and strain resistance they also deform more under the stress of mastication than porcelain veneers or facings. 

Various materials are used in dental prosthetic practice for the preparation of dental implants, crowns, and bridges. Some of these materials contain copper, which is added in order to improve mechanical or/and chemical properties, but some of them may contain the copper as an impurity. Considering the fact that dental implants remain in the oral cavity for a long time, and that they are exposed to the corrosive action of oral fluids and various kinds of food and beverages, it is necessary to check their possible harmful effects upon the human health. 

Anusavice, K. J. Council on Dental Materials, Instruments and Equipment Report on Base Metal Alloys for Crown and Bridge Applications Benefits and Risks , Journal of the American Dental Association, 111, 479-483 (1985)... 

Gulabivala, K., Setchell, D. J. Davies, E. H. (1987). An application of the jet test method for the evaluation of disintegration of dental luting cements in marginal gaps analogous to those of crowns and bridges. Clinical Materials,... 

Anusavice KJ. 1985. Report on base alloys for crown and bridge applications Benefits and risks. J Am Dent Assoc 111 479-483. 

Crosslinkable polyhedral oligomeric silsesquioxane, (11), prepared by Jin [2] were used as dental composites in restorative applications, especially in crown and bridge materials. 

Crown and bridge casting alloys (conventional alloys)... 

T. Moritz. D. Linaschke, and W. Eiselt. Development of ceramic crowns and bridges using electrophoretic deposition. Key Eng. Mater., 314, 207-12 (2006). 

B ourier Transform Infrared Spectrometry (F IR) Four crown and bridge alloys, alloys A, B. C. and E in Table I,... 

Dental crowns and bridges consist of a metal substrate covered by multiple layers of porcelain and glass. The first layer of porcelain must be opaque to hide the metal, while subsequent layers provide color matching to the surrounding teeth, and the correct luster and translu-cency to match the appearance of natural teeth. Good thermal compatibility between the various layers is essential to prevent thermal shock cracking, and to minimize residual stresses which could lead to stress-corrosion failures, or failure due to the combined residual and masticatory stresses. 

E2 Ivoclar Vivadent / IPS Empress 2 Heat-pressed, glass-ceramic with lithium disilicate, used as core material in crowns and bridges... 

L. Probster and J, Diehl, Slip-Casting Alumina Ceramics for Crown and Bridge Restorations, intessence Ini., 23,25-31 (1992). 

Uses methacrylic component in dental materials, such as crown and bridge products in artificial nails A... 

---