Mandibular first premolar: FDI 34 and 44

The numbers on both sides

In FDI the first digit is the quadrant and the second is the position counted from the midline. 34 is quadrant 3, position 4: the lower left first premolar. 44 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 21 on the lower left and 28 on the lower right. Palmer writes the position inside a bracket that shows the quadrant. In plain text that gives LL4 and LR4.

Crown surfaces: mesial, distal, buccal, lingual and occlusal.

The ADA chart also uses the older name first bicuspid.

Development and eruption

Calcification starts between 1.5 and 2 years and the crown is complete at 5 to 6 years. The tooth erupts at 10 to 12 years, after the lower canine, and the root closes at 12 to 13 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 crown is rhomboid and tilts toward the tongue. The buccal cusp is large and does the work, and from the cheek side the tooth resembles the mandibular canine. The lingual cusp is a small tubercle that plays little part in chewing.

A transverse ridge joins the two cusps and divides a linear mesial fossa from a rounder distal fossa. The mesial marginal ridge is shorter and is crossed by the mesiolingual groove, the most characteristic feature of the tooth. That groove helps tell the right tooth from the left and, like other fissures, can hold plaque.

Read on 24 October 2026. Sources: Nagas and others, The Permanent Maxillary and Mandibular Premolar Teeth, in Dental Anatomy (IntechOpen, 2018); 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

The root is usually single, straight, tapering and often curved distally. Ingle's Endodontics tabulates one root and one canal, but the canal often divides in the middle or apical third.

A pooled analysis of 8,677 teeth from 22 studies found 85.20 percent single rooted, 11.20 percent two rooted and 2.50 percent three rooted. Vertucci type I, one canal from orifice to apex, was 74.34 percent and type V was 15.45 percent. A systematic review of C-shaped canals reports a pooled 8.4 percent for this tooth.

Read on 24 October 2026. Sources: Number of roots and canals, from Ingle's Endodontics (animated-teeth.com); Karobari and others, Roots and Root Canals Characterization of Permanent Mandibular Premolars, J Clin Med 2023; Yousefi and others, Prevalence of c-shaped canal morphology in premolar and molar teeth assessed by CBCT, BMC Oral Health 2025. Figures are usual values, and teeth vary from person to person.

Neighbors and the baby tooth before it

Compared with the second premolar, the first is smaller and has one functioning cusp. The second premolar has a broader table that works like a molar. Compared with the canine, its crown is shorter, although it has almost the same width cheek to tongue.

It replaces the primary mandibular first molar, a tooth that resembles no permanent tooth. The primary molar has four cusps, a prominent mesial marginal ridge and a transverse ridge across the table.

Read on 24 October 2026. Sources: Nagas and others, The Permanent Maxillary and Mandibular Premolar Teeth, in Dental Anatomy (IntechOpen, 2018); MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.); Chussid, Anatomy of Primary Teeth, Columbia University College of Dental Medicine lecture. Figures are usual values, and teeth vary from person to person.

Local anesthesia

The inferior alveolar block reaches the tooth. Because the premolar sits in front of the mental foramen, an incisive nerve block also gives pulpal anesthesia, and leaves the tongue alone.

A mental nerve block, given at the fold by the second premolar, numbs the lip, chin and buccal mucosa in front of the foramen, but it does not reliably numb the pulp. The foramen itself most often lies under the second premolar.

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

On a radiograph, a canal that vanishes in the middle of the root is the fast break that signals a division. Branches are smaller than the parent canal, so the outline seems to disappear. The sign should prompt a search for a second canal.

With 15.45 percent of teeth falling into Vertucci type V and a meaningful share of two-rooted teeth, a lower first premolar that looks simple can hide an untreated branch, one of the exceptions behind persistent disease in single-rooted teeth.

Read on 24 October 2026. Sources: MolarPath note Pulp chambers and root canal morphology (built on Cohen's Pathways of the Pulp, 12th ed.); Karobari and others, Roots and Root Canals Characterization of Permanent Mandibular Premolars, J Clin Med 2023. 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); Karobari and others, Roots and Root Canals Characterization of Permanent Mandibular Premolars, J Clin Med 2023; MolarPath note Pulp chambers and root canal morphology (built on Cohen's Pathways of the Pulp, 12th ed.); Nagas and others, The Permanent Maxillary and Mandibular Premolar Teeth, in Dental Anatomy (IntechOpen, 2018). Figures are usual values, and teeth vary from person to person.