Maxillary central incisor: FDI 11 and 21

The numbers on both sides

In FDI the first digit is the quadrant and the second is the position counted from the midline. 11 is quadrant 1, position 1: the upper right central incisor. 21 is the same position in quadrant 2, on the upper left. Universal numbers adult teeth from 1 at the upper right third molar around to 32 at the lower right third molar, which makes this tooth 8 on the upper right and 9 on the upper left. Palmer writes the position inside a bracket that shows the quadrant. In plain text that gives UR1 and UL1.

A plain number can name two different teeth, so the system matters. Universal 11 is the maxillary left canine, which is FDI 23. Universal 21 is the mandibular left first premolar, which is FDI 34.

Crown surfaces: mesial, distal, labial (facial), lingual and incisal.

Development and eruption

Calcification starts a few months after birth, so the crown is finished by about 4 to 5 years, well before the tooth shows. It comes in behind the mandibular incisors and after the first molar. The root is only finished about two to three years after eruption, which explains the wide open apex on a radiograph of a 7-year-old.

Read on 24 October 2026. Sources: Human tooth development, tables citing Ash and Nelson, Wheeler's Dental Anatomy, Physiology and Occlusion (Wikipedia); American Dental Association, Tooth development charts (primary and permanent); MolarPath note Eruption sequence and chronology (built on McDonald and Avery, 11th ed., and Proffit's Contemporary Orthodontics, 7th ed.). Figures are usual values, and teeth vary from person to person.

Crown

The maxillary central incisor has the largest crown of the four incisors. From the front its outline is trapezoidal. In one tabulated set of mean measurements the crown is 10.5 mm long and 8.5 mm wide at the contact level, with 7.0 mm at the cervical line.

Behind the crown a rounded cingulum sits near the gum, and a shallow lingual fossa lies between the mesial and distal marginal ridges. On a freshly erupted tooth the incisal edge is scalloped by mamelons. The mesioincisal angle is close to a right angle and the distoincisal angle is rounder, which lets a clinician tell mesial from distal on an extracted tooth.

The mesial contact lies in the incisal third, close to the mesioincisal angle. The distal contact sits lower, at the junction of the incisal and middle thirds, so the two embrasures differ in size.

Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); MolarPath note Permanent tooth morphology (built on Wheeler's Dental Anatomy, 11th ed., and Sturdevant's Operative Dentistry, 8th ed.). Figures are usual values, and teeth vary from person to person.

Roots and canals

There is one root, cone shaped with a blunt apex, usually about 3 mm longer than the crown (13.0 mm in the same tabulated means). Ingle's Endodontics tabulates one root and one canal for every upper incisor.

The pulp is wider mesiodistally than labiopalatally. When the mamelons are well developed the chamber has three pulp horns, and the apical foramen can open a little off center.

Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); Number of roots and canals, from Ingle's Endodontics (animated-teeth.com). Figures are usual values, and teeth vary from person to person.

Neighbors and the baby tooth before it

Beside it, the lateral incisor is smaller in every dimension, has rounder incisal angles and a deeper palatal fossa. Across the arch the mandibular central incisor is the smallest crown in the mouth, 5.0 mm wide at contact against 8.5 mm here.

The primary predecessor is the primary maxillary central incisor, the only primary incisor with a crown wider than it is tall. The permanent germ lies lingual to the primary root, so the primary root starts to resorb on its lingual surface. A primary central incisor sheds at 6 to 7 years and its successor appears at 7 to 8 years.

Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.); MolarPath note Eruption sequence and chronology (built on McDonald and Avery, 11th ed., and Proffit's Contemporary Orthodontics, 7th ed.). Figures are usual values, and teeth vary from person to person.

Local anesthesia

The anterior superior alveolar nerve supplies the upper incisors and canine. A buccal infiltration over the root apex is the usual choice for a single tooth, because the buccal cortex over the incisors is thin. The palatal tissue behind the central incisors belongs to the nasopalatine nerve, which leaves the incisive foramen under the incisive papilla.

An infraorbital block reaches the anterior teeth as well, but it places solution far from the field and gives no bleeding control, so flap surgery still needs a local infiltration with vasoconstrictor.

Read on 24 October 2026. Sources: MolarPath note Maxillary techniques, local anesthesia (built on Malamed's Handbook of Local Anesthesia, 7th ed.). Figures are usual values, and teeth vary from person to person.

Clinical and exam points

Among the incisors, the incisor chapter in Dental Anatomy (IntechOpen) names this tooth as the one most likely to carry a talon cusp and the one most likely to be dilacerated. A mesiodens can develop between the central incisor roots, and a large labial frenum can leave a gap between the two teeth.

The AAPD notes that maxillary incisors can erupt ectopically or stay impacted behind a supernumerary tooth in up to two percent of the population, and that removing an erupted mesiodens lets the neighboring incisor erupt in 75 percent of cases. Ectopic eruption of a permanent incisor should be suspected after trauma to a primary incisor or when a primary incisor has had pulp treatment.

Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry (2024 revision). Figures are usual values, and teeth vary from person to person.

Questions and answers

Read on 24 October 2026. Sources: American Dental Association, Tooth development charts (primary and permanent); Human tooth development, tables citing Ash and Nelson, Wheeler's Dental Anatomy, Physiology and Occlusion (Wikipedia); Number of roots and canals, from Ingle's Endodontics (animated-teeth.com); Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017). Figures are usual values, and teeth vary from person to person.