Dental Materials
Select any two commonly used dental materials and their characteristic parameters (based on your background information on stress strain relation of materials).
Dental Amalgam
Dental amalgam is a mixture of elementary mercury (at about 43% to 54%) and an alloy powder (at about 46% to 57%) that consists primarily of silver, tin, and copper. Considerable attention has been given in the dental industry to the fact that dental amalgam contains heavy metals. Dental amalgam is durable and long lasting; it holds up well to the forces of biting and generally wears well. The substance is self-sealing and resists leakage, as it exhibits little to no shrinkage. Dental amalgam restoration is typically completed in one visit, and the frequency of repair and replacement is low. Dental amalgam restoration resists future decay at a high level, but when dental decay does occur in tooth surfaces repaired by dental amalgam, it is difficult to detect in the early stages.
The primary disadvantages of dental amalgam are that repair with the substance requires removal of some of the healthy tooth, and in larger dental amalgam fillings, the tooth that remains may be weaken such that it eventually fractures. Moreover, the metal in the dental amalgam mixture can conduct hot and cold temperatures, thereby contributing to tooth sensitivity -- although it is typically a temporary sensation. Also, the metal conductivity may result in very brief electrical flow when the dental amalgam contacts other metals. The cosmetic considerations...
Composite resin can be used for a number of different types of purposes, including fillings, inlays, partial or complete crowns, veneers, or to repair broken teeth. Composite resins may contain crystalline silica, a substance known to cause cancer. Composite resins are known to be durable and strong. An important attribute of composite resins is that it resists breakage, typically holding up well to the forces exerted by biting and chewing. There is little risk of leakage when composite resins are bonded only to tooth enamel. Composite resins do not corrode, and the frequency of replacement or repair is moderate. The resistance to further decay with composite resins is moderate and easy to find. The application of composite resins for fillings can be accomplished in single visits.
The primary disadvantages of composite resins are costs -- which are considerably more than dental amalgams -- and that the material may shrink as it hardens, which can lead to further decay and/or sensitivity to temperature changes. Composite resins are considered to wear down faster than dental enamel, and leakage may occur when composite resins are bonded underneath a…
