Tooth 21 (FDI): maxillary left central incisor

The three numbers

Careful with plain numbers: Universal 21 is a different tooth, the mandibular left first premolar (FDI 34).

About this tooth

Name

Maxillary left central incisor

Set

Adult (permanent)

Position

Upper arch, patient left (upper left, quadrant 2)

Erupts

7 to 8 years

Roots

1

Root canals

1

Crown surfaces

Mesial, distal, labial (facial), lingual and incisal.

Also written

#9 (Universal), 2.1 (FDI with a dot), upper left 1

Read on 23 October 2026. Sources: American Dental Association, Tooth development charts (primary and permanent); Number of roots and canals, from Ingle's Endodontics; Dental anatomy, citing Ash and Nelson, Wheeler's Dental Anatomy, Physiology and Occlusion. Ages and counts are usual figures, and teeth vary from person to person.

On the chart

Teeth next to it

• Toward the middle: 11 (maxillary right central incisor)
• Toward the back: 22 (maxillary left lateral incisor)
• Across the midline: 11 (maxillary right central incisor)
• In the other arch: 31 (mandibular left central incisor)

Convert any other tooth with the full chart.