Which classification involves the interproximal surface of a posterior tooth?

• A. Class I
• B. Class III
• C. Class II
• D. Class V

Answer: (C)

Understanding how surfaces are classified helps you identify where a decay or restoration sits. The interproximal surface between two back teeth is a proximal surface of a posterior tooth, which is categorized as Class II. This class specifically covers the mesial or distal sides of premolars and molars that touch adjacent teeth. Other classifications describe different areas: Class I targets pits and fissures on occlusal surfaces of posterior teeth (and some other surfaces), Class III and Class IV involve proximal surfaces of anterior teeth (with or without involving the incisal edge), and Class V covers the cervical third of facial or lingual surfaces of any tooth. So, the surface described in the question is the proximal surface of a posterior tooth, i.e., Class II.