approximal, interproximal

What is the approximal surface?

It is the contact surface facing the adjacent tooth. Approximal is therefore a collective term that divides into two directions: mesial faces towards the midline of the dental arch, distal faces away from it. Tooth 36 therefore has a mesial surface facing tooth 35 and a distal surface facing tooth 37. In anatomy one also encounters proximal, which generally means “close to the body” and is not synonymous with approximal.

Why this area is clinically challenging

Toothbrushes cannot reach the approximal surfaces. For this reason caries develops there particularly frequently, and it remains invisible for a long time because the adjacent tooth blocks the view. It is usually detected on a bitewing radiograph. In Black's cavity classification system, approximal lesions on posterior teeth fall under Class II, and on anterior teeth under Class III. Dental floss and interdental brushes are the standard recommendation here. When placing a filling, restoring a firm contact point with the adjacent tooth is critical: if it remains too weak, food debris accumulates and the defect recurs.

How is the term recorded?

Together with the tooth number under the FDI tooth numbering system and other surfaces, the usual shorthand notation results. “mo at 16” denotes a mesio-occlusal filling on the upper right first molar. In English-medium teaching in Hungary, Romania, Bulgaria, or Croatia the term is “approximal” or “interproximal”, the meaning being the same. Anyone taking over previous findings from abroad should check which numbering system is used, otherwise the notation shifts by an entire quadrant. If in doubt, a look at the associated radiograph helps.