Black's Classification of Cavities

Class 1
Decay is diagnosed in the pits and fissures of the occlusal surfaces of molars and premolars, the buccal or lingual pits of molars, and the lingual pits of maxillary incisors. 
Restore: Amalgam or composite resins are the restorative material of choice. Selection will depend primarily on where the lesion is and what type of strength is required for the material.

Class 2
Decay is diagnosed in the proximal (mesial or distal) surfaces of premolars and molars. Because this surface area is more difficult to detect visually, a radiograph is also used to locate decay. The design of the preparation/restoration will include the occlusal surface and will involve proximal surfaces. 
Restore: The type of dental material used to restore this classification is silver amalgam (chosen for its strength) or newer composite (tooth-colored) resins designed for posterior teeth (chosen for esthetic appeal). If the tooth has extensive decay, the dentist may choose to restore the tooth with a gold or porcelain inlay, onlay, or crown.

Class 3
Decay is diagnosed in the proximal (mesial or distal) surfaces of incisors and canines. This decay is similar to class 2, except that it involves anterior teeth. It is easier for the dentist to access these surfaces with less tooth structure affected. 
Restore: The type of dental material used to restore this classification consists of composite (tooth-colored) resins (for esthetic appearance).




 
Class 4
Decay is diagnosed in the proximal (mesial or distal) surfaces of incisors and canines. The difference between class 4 and class 3 decay is that class 4 involves the incisal edge or angle of the tooth. 
Restore: The type of dental material used to restore this classification is composite (tooth-colored) resins (for esthetic appearance). If the tooth has extensive decay, the dentist may choose to restore the tooth with a porcelain crown.


Class 5
Decay is diagnosed in the gingival third of the facial or lingual surface of any tooth. This is also referred to as smooth-surface decay. 
Restore: The type of dental material used to restore this classification depends on which teeth are affected. If decay occurs in posterior teeth, the dentist may choose silver amalgam; if anterior teeth are involved, composite (tooth-colored) resin will most likely be used.

Class 6
Decay is diagnosed on the incisal edges of the anterior teeth and the cusp tips of the posterior teeth. Class 4 decay is caused by abrasion (wear) and defects. 
Restore: The dental material is chosen on the basis of which teeth are involved.