Maxillary second premolar: FDI 15 and 25

The numbers on both sides

In FDI the first digit is the quadrant and the second is the position counted from the midline. 15 is quadrant 1, position 5: the upper right second premolar. 25 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 4 on the upper right and 13 on the upper left. Palmer writes the position inside a bracket that shows the quadrant. In plain text that gives UR5 and UL5.

A plain number can name two different teeth, so the system matters. Universal 15 is the maxillary left second molar, which is FDI 27. Universal 25 is the mandibular right central incisor, which is FDI 41.

Crown surfaces: mesial, distal, buccal, palatal (lingual) and occlusal.

The ADA chart also uses the older name second bicuspid.

Development and eruption

Calcification starts at 2 to 2.25 years and the crown is complete at 6 to 7 years. Eruption is at 10 to 12 years and the root is done at 12 to 14 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 rounder and less angular than the first premolar, and usually a little smaller from the biting edge to the neck and from front to back. Its two cusps are nearly equal, the buccal one slightly shorter and less pointed than the one on the first premolar.

The occlusal outline is oval. The grooves are shorter, shallower and more irregular, with many supplemental lines that give the surface a wrinkled look. The mesial developmental depression of the first premolar is absent, so there is no canine fossa.

Read on 24 October 2026. Sources: 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.

Roots and canals

One root is usual, with a longitudinal groove on the mesial and distal faces. The root splits in about 15 percent of teeth in the premolar chapter of Dental Anatomy, and the tip is often deflected distally. Ingle's Endodontics tabulates one root and one or two canals.

The distal contact is with the first molar, so it is larger than the mesial contact, and both contacts sit slightly lower than on the first premolar.

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

The main differences from its neighbor are the equal cusps, the oval outline and the missing mesial depression. The mandibular second premolar, in contrast, usually has three cusps.

It replaces the primary maxillary second molar, which resembles a small permanent first molar and is wider mesiodistally than the premolar. That width difference creates the leeway space: about 1.5 mm per side in the maxilla, by the figures in Proffit.

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.); 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 middle superior alveolar block is placed above this tooth, at the height of the mucobuccal fold, and works where the nerve exists. A buccal infiltration at the apex covers it in most adults, and a small palatal injection helps when the palatal margin is involved.

A small palatal infiltration in attached gingiva gives enough soft tissue anesthesia for one or two teeth. Fast or large palatal deposits cause pain and prolonged blanching.

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

The AAPD names the maxillary second premolar as the third most frequently missing permanent tooth, after the mandibular second premolar and the maxillary lateral incisor, with third molars left out.

When a premolar is congenitally absent the primary molar can be kept or taken out. Keeping it may cause occlusal problems because of its width, and the AAPD adds that a submerged, ankylosed tooth can leave a bone defect that complicates a later implant. A sound primary molar with no successor can often serve for many years.

Read on 24 October 2026. Sources: American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry (2024 revision); 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.

Questions and answers

Read on 24 October 2026. Sources: American Dental Association, Tooth development charts (primary and permanent); American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry (2024 revision); 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.