Classification+of+Caries+and+Preparations

==

Class 1 (I)
lesions occur in pits and fissures on the facial, lingual, and occlusal surfaces of molars and premolars and, less often, the lingual surfaces of maxillary anterior teeth (most frequently lateral incisors, less frequently central incisors, rarely canines).

Class 2 (II)
lesions occur in the proximal surfaces of the posterior teeth (molars and premolars). If a proximal surface of a posterior tooth is involved in a restoration, it is a Class 2 restoration.

Class 3 (III)
lesions occur in the proximal surfaces of anterior teeth (central and lateral incisors and canines). Class 3 cavities do not involve an incisal angle.

Class 4 (IV)
lesions occur in the proximal surfaces of anterior teeth when the incisal angle requires restoration. The angle may have to be removed because of its fragility or for proper placement of the restoration, or it may have been fractured by trauma.

Class 5 (V)
lesions occur in smooth facial and lingual surfaces in the gingival third of teeth. Class 5 lesions begin close to the gingiva and may involve a cementum or dentin surface as well as enamel.

Class 6 (VI)
lesions are in pit or wear defects on the incisal edges of anterior teeth or the cusp tips of posterior teeth. In addition to being named for their classifications, cavity preparations and restorations are named for the tooth surfaces involved. For example, a restoration involving the mesial and occlusal surfaces of a posterior tooth is called a mesio-occlusal Class 2 restoration; simply saying mesio-occlusal restoration identifies it as a Class 2 restoration because the proximal surface of a posterior tooth is involved. A preparation or restoration involving the mesial, occlusal, distal, and facial surfaces of a posterior tooth is called a mesio-occlusodistofacial preparation or restoration.

(Summitt 129) Summitt, James B.. Fundamentals of Operative Dentistry: A Contemporary Approach, 3rd Edition. Quintessence Publishing (IL), 012006. .