Biomedical Engineering Reference
In-Depth Information
Fig. 6.2
The maximum depth, width, and volume of the wear loss of the wear scars for the fi ve
types of resin composites under different kinds of lubrication [
22
]
6.2
Wear Behavior of Dental Alloys
Dental alloys, with favorable mechanical properties, have been studied and applied
extensively as dental materials for over a century. Generally, most metals are strong
enough to withstand the maximum possible oral forces and have been found to be
competitive among dental materials. Dental metallic materials can be classifi ed as
noble alloys and base alloys. The International Organization for Standardization
(ISO), the American Dental Association (ADA), and the Chinese national standard
(GB) have defi ned clearly that an alloy in which the net content of one or several
kinds of noble metal is no less than 25 % is called a “noble metal alloy.” A noble
metal element is defi ned as the element that can retain a favorable metal surface. It
can react with brimstone easily to become sulfi de. Because of singular antioxida-
tion, excellent resistance to corrosion, and satisfactory burnish in heating, casting,
and welding, noble metals have become the ideal metal materials in dentistry. Noble
metal elements include Au, Pd, Pt, Ir, Rh, Os, and Ru. In dentistry, the base metal
element is the element added in noble metal alloy. They include Ag, Cu, Zn, Sn, In,
Ga, Ni, and others, which can improve the mechanical function of the noble metal
alloy. Ag has been confi rmed as the best conductor among heat and electricity. It
cannot degenerate in any centidegree among clean and dry air, but it can combine
with S, Cl, and P or these compounds. Because these reactions will cause a
discoloration in Ag, it cannot be used in dentistry. Other base metal elements mainly
