Palladium dental alloy

The main uses of palladium [13] are in the electronics and electrical industries, in circuitry and in dental alloys. It finds many catalytic applications in industry, as well as in diffusion cells for the synthesis of hydrogen, and in automobile catalysts. Jewellery and three way auto-catalysts are the principal uses of platinum, which fulfils a wide range of roles in the chemical industry. 

Siloxane compounds, in vitreous silica manufacture, 22 414 Siloxane materials, 20 240 Siloxane oligomers, in silicone polymerization, 22 555-556 Siloxanols, silylation and, 22 703 Silsesquioxane hybrids, 13 549 Silsesquioxanes, 15 188, 22 589-590 SilvaGas process, 3 696, 697 Silver (Ag), 22 636-667. See also Silver compounds. See Ag entries Argentothiosulfate complexes Batch desilverizing Lead-silver alloys Palladium-silver alloy membranes analytical methods for, 22 650-651 applications of, 22 636-637, 657-662 as bactericide, 22 656, 657, 660 barium alloys with, 3 344 in bimetallic monetary system, 22 647-648 in cast dental gold alloys, 8 307t coke formation on, 5 266 colloidal precipitation color, 7 343t colloidal suspensions, 7 275 color, 7 334, 335... 

Ruthenium alloyed to platinum, palladium, titanium and molybdenum have many apphcations. It is an effective hardening element for platinum and palladium. Such alloys have high resistance to corrosion and oxidation and are used to make electrical contacts for resistance to severe wear. Ruthenium-palladium alloys are used in jewelry, decorations, and dental work. Addition of 0.1% ruthenium markedly improves corrosion resistance of titanium. Ruthenium alloys make tips for fountain pen nibs, instrument pivots, and electrical goods. Ruthenium catalysts are used in selective hydrogenation of carbonyl groups to convert aldehydes and ketones to alcohols. 

Palladium silver alloys admit of receiving a high polish, and retain their bright surface. An alloy containing 38 per cent, of palladium, the remainder being silver, was formerly used for dental purposes. 

In a pursuit to design new low cost alloys, XPS has been used to analyze the oxidation state of palladium in dental alloys at the surface and at depths of 30, 100, and 1,000 A. The results are as shown in Fig. 5.19. 

Palladium is used in the electronics and chemical industries, but there are no convincing case reports on work-related allergic contact dermatitis. Instead, the exposure has mainly been from jewelry and dental alloys (Aberer et al. 1993). The majority of patch-test positive patients show concomitant reactivity to nickel this has been interpreted as a sign of cross-reactivity. Patients who patch-test positive to palladium chloride rarely react when tested with palladium discs (Todd and Burrows 1992 de Fine Olivarius and Menne 1992). Palladium chloride is a potent sensitizer in the guinea pig, and animals induced with palladium chloride also react to nickel at patch testing (Wahlberg and Boman 1992). 

Aberer W, Holub H, Strohal R, et al. (1993) Palladium in dental alloys - the dermatologists responsibility to warn Contact Dermatitis 28 163-165... 

In Japan, aU government-subsidized dental alloys must have a palladium content of at least 20 percent. 

Another 10% end-user of palladium is dentistry. By alloying it with palladium dental gold can be made harder and more wear resistant The introduction of more gold covering of porcelain crowns has increased this palladium use. 

The addition of 10 wt% palladium renders the alloy white (or silver) in color and shifts the hardening mechanism to solid-solution strengthening. Base element additions are indium, tin, gallium, and zinc. These are the most popular dental alloys because they can be easily modified to suit different porcelains and economic needs. 

Dentistry. Most casting alloys meet the composition and properties criteria of specification no. 5 of the American Dental Association (37) which prescribes four types of alloy systems constituted of gold—silver—copper with addition of platinum, palladium, and 2inc. Composition ranges are specified, as are mechanical properties and minimum fusion temperatures. Wrought alloys for plates also may include the same constituents. Similarly, specification no. 7 prescribes nickel and two types of alloys for dental wires with the same alloy constituents (see Dental materials). 

Alloys suitable for castings that ate to be bonded to porcelain must have expansion coefficients matching those of porcelain as well as soHdus temperatures above that at which the ceramic is fired. These ate composed of gold and palladium and small quantities of other constituents silver, calcium, iron, indium, tin, iridium, rhenium, and rhodium. The readily oxidi2able components increase the bond strength with the porcelain by chemical interaction of the oxidi2ed species with the oxide system of the enamel (see Dental materials). 

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. 

Copper [7440-50-8] Cu, produces a reddish color and reduces the melting pokit of the alloy. It produces heat-treatable compositions with gold, platinum, and palladium that result ki kicreased hardness, strength, and generally improved physical properties. The tarnish resistance of the alloy is usually decreased. The gold—copper, Au—Cu, system is the fundamental system of many dental gold alloys. Copper has a useful range of 0—20 wt %. 

Platinum, as an alloying element, is used in many dental casting golds (Tables 6 and 7) to improve hardness and elastic qualities. Platinum in combination with palladium and iridium has limited use for dental pins and wires. 

Bessing, C., Bergman, M. and Thoren, A. Potentiodynamic Polarization Analysis of Low-gold and Silver-Palladium Alloys in Three Different media. Dental Materials, 3, 153-159 (1987)... 

Metzger, P. R., Vrijhoef, M. M. A. and Greener, E. H. Corrosion Resistance of Three High-Palladium Alloys , Dental Materials, 1, 177-179 (1985)... 

J. Begerow, L. Dunemann, Internal platinum and palladium exposure of the general population with emphasis on the exposure from automobile exhaust and dental restorative alloys, in F. Zereini, F. Alt (eds), Anthropogenic Platinum-group Element emissions. Their Impact on Man and Environment, Springer, Berlin, 2000, pp. 227 D 236. 

Uses.—Palladium is seldom used in the pure state, and its alloys have hitherto received but little application even in scientific work, although recently a useful field has been discovered for utilising certain alloys, such as those of palladium and gold, as substitutes for platinum. They have been used, on account of their excellent resistance to atmospheric corrosion, for certain astronomical and dental purposes, and for coating the surfaces of reflectors used for searchlights, etc. Palladium salts are used in photography. 

Dental amalgam (SEDA-10,210) (SEDA-15,233) (14,15) is still used for about 75-80% of single-tooth restorations. The modern amalgam consists of a metalhc alloy (silver, tin, and copper, sometimes with small amounts of zinc, indium, and/or palladium) mixed with mercury in a percentage of 40-54% mercury by weight. The resultant plastic mass sets and hardens over a period of 8-24 hours. 

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