Introduction to Dental Material

The primary objective of restorative dentistry is to replace diseased or lost tooth structure with materials that restore function and appearance. A variety of materials are used for different types of restorations. The restorative material must be selected before the tooth is prepared for restoration. Therefore understanding the properties that distinguish one material from another is important. A brief survey of the types of restorations, along with a description of restorative materials, illustrates the factors involved in the section process.
First a loss of tooth structure, which requires restoration of a portion of an anterior tooth, may be caused either by injury or by caries. Resin composite materials usually are chosen for this restorative task. These materials are shaded to match the teeth in appearance. Their strength is a secondary factore because the anterior teeh are usually not subject to high bitting force. Although resin composite materials are weaker than metals, their excellent appearance and acceptable durabillity are the main reason for their choise.

A mettalic restoration may be preferable to a resin composite material for the restoration of the portion of a posterior tooth subject to considerably greater bitting forces because of strength and wear resistance considerations. Because a posterior restoration is not noticeable, the appearance factor is not as important. However, increasing numbers of patients are requesting the placement of esthetic posterior  composite.
Dental silver amalgam restorations and  gold inlays are used most often for this type of posterior restoration. An amalgam paste is placed directly into the prepared tooth cavity and carved to the correct anatomy. An inlay is a restoration prepared outside the mouth and cemented to the prepared tooth.


The cavity preparation for the amalgam restoration is tappered so that it isnlarger at the base than at the occlusal surface. This design is necessary because amalgam cannot be bonded adequately to tooth structure and the restoration must be retained machanically. In addition, the cavity preparation for the gold alloy inlay is tappered so that the base is slightly smaller than the occlusal surface. This design is required because the solid cast gold alloy restoration must be able to be inserted and cemented to the cavity preparation.

The inlay involves the occlusal and proximal surface or surfaces of the tooth but also may cover one of the cusps of the posterior tooth. When the restoration involves the occlusal and proximal surface and surfaces and covers all the cusp it is called onlay.


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Taken from :
Dental Materials
Robert G. Craig