Australian Dental Council (ADC) Practice Test

A porcelain veneer may "pop off" from an underlying gold crown due to several factors that can compromise the bond between the porcelain and the metal. When considering the specifics:

The application of a thick layer of pure gold surface conditioner can negatively affect the bonding process. If the conditioner is too thick, it can lead to a weaker bond because the thickness may prevent the porcelain from adequately interacting with the metal surface, which is essential for achieving a strong attachment.

Contamination at the porcelain-metal interface is another critical factor. Any oils, moisture, or other contaminants present during the bonding process can create a barrier that inhibits proper adhesion of the porcelain to the crown. Such contamination can prevent the bonding materials from effectively creating a solid interface.

Underfiring the opaque layer also contributes to the risk of veneer failure. Proper firing temperature and duration are essential for ensuring that the porcelain achieves optimal physical properties and bond strength. If the opaque layer is underfired, it may not develop the necessary characteristics to bond well with the gold crown, leading to a failure of the veneer.

Considering all these factors, it is clear that each one can individually contribute to the "pop off" of the veneer. Therefore, the comprehensive nature of the potential issues points to "all of the