Which material is specifically mentioned as not being used directly on enamel?

Emery is a material that is specifically not used directly on enamel due to its abrasive nature. Emery contains aluminum oxide and is known for its coarse texture, making it suitable for shaping and polishing harder materials, but it can be too harsh for the delicate surface of enamel. Using such an abrasive material directly on enamel can lead to surface damage, microfractures, or the removal of enamel, which is critical to preserve for dental health.

In contrast, the other materials listed—pumice, silex, and whiting—are often utilized in dental procedures involving enamel because they are less abrasive and can effectively polish or clean enamel surfaces without causing significant damage. For instance, pumice is commonly used in dental prophylaxis to remove plaque and stains from teeth, while silex and whiting serve similar purposes in polishing. Thus, when considering safety and effectiveness in dental procedures, emery is understood to be inappropriate for use directly on enamel.