Hard tooth structure has been described as a composite material made up of enamel, mantle dentin, and the Dentino-Enamel Junction (DEJ). The surface hardness of enamel protects the tooth as it strikes against the opposing one, and guards the softer underlying DEJ and dentin. As it turns out, though, recent evidence suggests that enamel is not the inherently brittle material it was once believed to be.
Ceramics, such as those used for dental crowns, have a strong inter-atomic bond causing them to be brittle. Failure of brittle materials occurs because they have only limited ability to deform or "give" under pressure.
Natural dental enamel is composed of mineral crystals and protein. This composition enables the enamel to retain its structural integrity under bite force.
But the protein layers in the enamel give it a most interesting shearing characteristic, similar to that of metals - the atoms slip over one another when stress is applied. This enables the enamel to absorb a significant amount of pressure before it cracks. Since this physical property of gold mimics the natural characteristic (bio-mimetic) of dental enamel with regard to wear and fatigue, it is a superior choice for restoration compared to brittle materials such as ceramic or tooth-colored composites.
Additionally, it has been proven that dental ceramics, because of their inherent hardness, cause more wear on the antagonist dentition (the tooth opposite the ceramic crown) than does gold alloy. Dental materials with stress-strain responses more similar to those of natural enamel are less abrasiveness and better protect the opposing dentition. There is less stress concentrated at points where the teeth meet. Gold alloys possess these biomechanical characteristics as well as the ability to maintain their form long-term, more than any other material currently used in dentistry. Therefore, gold alloys function harmoniously with a patient's own dentition.
Build up of tooth with composite base prior to preparation