Each tooth surface has a name. For example, a cavity or another anomaly can be located on one or more surfaces of a tooth. In addition, billing for treatments is made by the surface, which explains why fillings on two different premolars may have different fees.
In writing, we use the first letter of the surface to describe the area in question. For example: tooth #37 O (O = occlusal).
Mesial = M
Lingual = L
Distal = D
Occlusal = O (for molars) or Incisal = I (for front teeth)