INBDE (Integrated National Board Dental Examination) Practice Exam

Is the failure or fracture usually on the porcelain-metal interface in metal-ceramic restorations?

1. Yes

2. No

3. Only in rare cases

4. Depends on the alloy used

The correct answer is: No

In metal-ceramic restorations, the failure or fracture is typically not on the porcelain-metal interface. This is because the bond between the metal and the porcelain is usually strong and well-established, especially when proper techniques are employed during the fabrication of the restoration. Instead, failures or fractures in metal-ceramic restorations commonly occur within the porcelain or the metal substructure itself due to various reasons such as incompatible coefficient of thermal expansion between the metal and porcelain, occlusal forces, or material defects. Therefore, the correct answer is "B. No." Option A is incorrect because, as explained, failures or fractures do not usually occur at the porcelain-metal interface. Option C is incorrect as well because it is not considered rare for failures or fractures to happen within the porcelain or the metal substructure rather than at the interface. Option D is incorrect because the location of failure or fracture in metal-ceramic restorations is not primarily dependent on the alloy used.