When is a Class II cavity preparation typically indicated?

A Class II cavity preparation is specifically indicated for cavities located on the mesial and distal surfaces of posterior teeth, such as molars and premolars. This type of preparation addresses interproximal decay that often occurs between two adjacent teeth. Since Class II preparations involve more than one surface, they require a distinct shape to adequately remove the decay and restore the integrity of the tooth.

In contrast, decay on the facial surface would typically be managed with a Class I or Class III preparation, making that option less relevant to the question. Incisal edge restorations refer to Class IV preparations, which involve the anterior teeth at the incisal edge and do not pertain to the interproximal areas targeted by Class II procedures. Treating deep caries can occur in a variety of cavity classes depending on the specific location and extent of decay, so it doesn't specifically indicate the need for a Class II cavity preparation. Thus, the choice correctly identifies the situation in which a Class II cavity preparation is typically indicated.