In the universal numbering system, which tooth corresponds to #21?

In the universal numbering system, each tooth is assigned a specific number to facilitate identification and communication about dental treatments. The numbering begins at the right maxillary third molar with the number 1 and continues sequentially across the upper arch to the left maxillary third molar, then it moves down to the lower arch starting from the left mandibular third molar, continuing to the right mandibular third molar, which is designated as number 32.

Tooth #21 specifically refers to the mandibular first premolar, which is accurately placed in the universal numbering system as follows: the mandibular teeth are numbered starting from 17 for the left mandibular third molar, moving sequentially to the right. The first premolar in the lower arch, which is the mandibular first premolar, corresponds to number 21. This knowledge is critical for dental professionals as accurate tooth identification is essential for treatment planning, patient communication, and record-keeping.