Mandibular lateral incisor: FDI 32 and 42
The second lower incisor: a little wider than its neighbor, with an incisal edge that slopes toward the back.
Quick answer
- FDI 32 and 42, Universal 23 and 26, Palmer LL2 and LR2.
- Mandibular lateral incisor erupts at 7 to 8 years.
The numbers on both sides
| Tooth | FDI | Universal | Palmer |
|---|---|---|---|
| Lower left lateral incisor | 32 | 23 | LL2 |
| Lower right lateral incisor | 42 | 26 | LR2 |
In FDI the first digit is the quadrant and the second is the position counted from the midline. 32 is quadrant 3, position 2: the lower left lateral incisor. 42 is the same position in quadrant 4, on the lower right. 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 23 on the lower left and 26 on the lower right. Palmer writes the position inside a bracket that shows the quadrant. In plain text that gives LL2 and LR2.
A plain number can name two different teeth, so the system matters. Universal 32 is the mandibular right third molar, which is FDI 48.
Crown surfaces: mesial, distal, labial (facial), lingual and incisal.
Development and eruption
| Stage | Age |
|---|---|
| Calcification begins | 3 to 4 months |
| Crown completed | 4 to 5 years |
| Erupts | 7 to 8 years |
| Root completed | 10 years |
Calcification starts at 3 to 4 months, as for the central incisor, but the tooth erupts a year later, at 7 to 8 years, and the root closes at about 10 years.
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). Figures are usual values, and teeth vary from person to person.
Crown
The lateral incisor resembles the central incisor without its symmetry. The labial outline is more fan shaped, the cingulum is shifted distally and the marginal ridges are faint. In the tabulated means the crown is 9.5 mm long and 5.5 mm wide at contact.
The incisal ridge slopes down toward the distal side, and the crown is twisted distolingually so it follows the curve of the arch. The distoincisal angle is rounder than the sharp mesioincisal angle. The distal contact is in the incisal third, but lower than the mesial contact.
Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017). Figures are usual values, and teeth vary from person to person.
Roots and canals
The root resembles the central incisor root, with mesial and distal depressions, and is slightly longer: 14.0 mm in the tabulated means against 12.5 mm. The socket is larger and deeper to hold it. Ingle's Endodontics tabulates one canal.
In the Chilean CBCT sample of 336 teeth, all lateral incisors had one root and 31.5 percent had two canals. The pooled Chinese figure was 14.1 percent, from 798 of 5,647 teeth.
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); Betancourt and others, CBCT assessment of root and canal morphology in mandibular anterior teeth in a Chilean subpopulation, BMC Oral Health 2026; Aung and Myint, Evidence of Second Canal between Permanent Mandibular Central and Lateral Incisors in China, Int J Dent 2020. Figures are usual values, and teeth vary from person to person.
Neighbors and the baby tooth before it
The lateral incisor is slightly wider than the central incisor, and its incisal edge tilts distally where the central incisor's is straight. Next to it, the canine has a longer crown and a single cusp.
The primary mandibular lateral incisor has a rounder distoincisal angle than its central neighbor, and neither primary lower incisor has mamelons. The primary tooth sheds at 7 to 8 years.
Read on 24 October 2026. Sources: Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); Chussid, Anatomy of Primary Teeth, Columbia University College of Dental Medicine lecture; MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.); American Dental Association, Tooth development charts (primary and permanent). Figures are usual values, and teeth vary from person to person.
Local anesthesia
The inferior alveolar nerve reaches the tooth, and the incisive nerve is the part of it that supplies the teeth in front of the mental foramen. Infiltration also works at this site in adults, since in the lower arch it works mainly for teeth in front of the molars.
A mental nerve block, given in the fold at the second premolar, numbs the lip and chin but does not reliably give pulpal anesthesia. Pressing on the site afterward moves the solution into the foramen and turns it into an incisive block.
Read on 24 October 2026. Sources: MolarPath note Mandibular 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
Most of the increase in lower intercanine width happens as the lateral incisors take their place, with little change when the canines erupt.
The AAPD lists interproximal stripping of the mandibular primary canines as one way to make room for crowded permanent lateral incisors. Anomalies are rare in this tooth, though a bifurcated root is occasionally seen.
The permanent lateral incisor is wider than the primary lateral incisor it replaces. Across the four lower incisors the difference, called the incisor liability, is about 6 mm, and a spaced primary arch is what makes room for it.
Read on 24 October 2026. Sources: MolarPath note Eruption sequence and chronology (built on McDonald and Avery, 11th ed., and Proffit's Contemporary Orthodontics, 7th ed.); American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry (2024 revision); Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017). Figures are usual values, and teeth vary from person to person.
Questions and answers
What are the numbers for the mandibular lateral incisor?
FDI 32 and 42, Universal 23 and 26, Palmer LL2 and LR2.
How is the lateral different from the central?
It is slightly wider, its incisal edge slopes distally and its cingulum shifts toward the distal side.
How often does it have two canals?
In a Chilean CBCT sample, 31.5 percent of 336 teeth. A pooled analysis of Chinese studies gave 14.1 percent.
When does it erupt?
The ADA chart gives 7 to 8 years.
Read on 24 October 2026. Sources: American Dental Association, Tooth development charts (primary and permanent); Grawish and others, Permanent Maxillary and Mandibular Incisors, in Dental Anatomy (IntechOpen, 2017); Betancourt and others, CBCT assessment of root and canal morphology in mandibular anterior teeth in a Chilean subpopulation, BMC Oral Health 2026; Aung and Myint, Evidence of Second Canal between Permanent Mandibular Central and Lateral Incisors in China, Int J Dent 2020. Figures are usual values, and teeth vary from person to person.
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