Advances in dental ceramics/ dental implant courses by Indian dental academy

Fired onto the opaque layer, usually in conjunction with the incisal porcelain. It provides some translucency and contains oxide that aid shade matching. Body porcelains are available in a wide selection of shades matching. Body porcelains are available in a wide section of shades to match adjacent natural teeth. Most porcelain manufactures provide an opaque shade for each body shade.

Incisal porcelain: Usually translucent. As a result, the perceived color of the restoration is significantly influenced by the color of the underlying body porcelain.

Porcelain – alloy bonding: • Oxide layer formation  degassing conditioning bake oxidation • The linear coefficients of thermal expansion for the metal and ceramic must closely match to achieve a strong interfacial bond. αm = 13.5 to 14.5 x 10-6/0C αl = 13.0 to 14.0 x 10-6/0C The slightly higher coefficient for the metal causes the ceramic to be in a beneficial state of residual compressive stress at room temperature.

Interfacial bond should be strong enough so that fracture occurs entirely with in porcelain.

• Metal ceramic bond should exceed (28 mpa) to have cohesive failure through the porcelain rather than failure at interface.

• Another philosophical change in the recommended method for evaluating the metal-ceramic bond appears to be underway with the introduction of ISO standard No 9693 for dental porcelain