Primary maxillary first molar: FDI 54 and 64

The numbers on both sides

In FDI the first digit is the quadrant and the second is the position counted from the midline. 54 is quadrant 5, position 4: the upper right primary first molar. 64 is the same position in quadrant 6, on the upper left. Universal gives baby teeth the letters A to T, from the upper right second molar around to the lower right second molar, which makes this tooth B on the upper right and I on the upper left. Palmer writes the letter for the position inside a bracket that shows the quadrant. In plain text that gives URD and ULD.

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

Development and eruption

Calcification starts at about 15.5 weeks in utero and the crown is complete at 6 months. The tooth erupts at 13 to 19 months, after the incisors, and the root is complete at 2.5 years. It is shed at 9 to 11 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

This tooth is atypical. It looks more like a premolar than a molar, with three or four cusps and a prominent mesiobuccal cervical tubercle, a bulge near the gum on the cheek side. One primary anatomy lecture sums it up as a molar with a unique look and three cusps.

The crown is short and squat for its width and narrows sharply at the neck. The enamel is about half as thick as permanent enamel, and the contacts with neighboring teeth are broad and flat, so proximal surfaces are common caries sites when the arch has no spaces.

Read on 24 October 2026. Sources: 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.

Roots and canals

Three widely divergent roots hold the tooth, two on the cheek side (mesiobuccal and distobuccal) and one palatal. A CBCT study of 1,002 maxillary primary molars in 268 children aged 3 to 7 years found three roots in 57.9 percent of the first molars. Most roots held one canal, and a second canal in the mesiobuccal root appeared in 2.2 percent of the first molars.

The short root trunk puts the furcation near the neck. The floor is thin and porous, with accessory canals opening into the furcation. The wide spread of the roots leaves room for the premolar crown between them.

Read on 24 October 2026. Sources: Kim and others, Root and Canal Morphology of Maxillary Primary Molar using CBCT and 3D CT, Journal of the Korean Academy of Pediatric Dentistry 2021; Kirilova and others, Micro-CT Assessment of Dentin Mineral Density and Furcation Morphology in Primary First and Second Molars, Dentistry Journal 2026; MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.); Salama and others, Anatomy of primary incisor and molar root canals, Pediatric Dentistry 14(2), 1992. Figures are usual values, and teeth vary from person to person.

Neighbors and the tooth that replaces it

The second molar beside it is larger and looks like a small permanent first molar. The first molar is the odd one, and the AAPD notes that hypodontia in the primary dentition almost always involves the maxillary incisors and the first primary molars, at under one percent.

The successor is the maxillary first premolar, which erupts at 10 to 11 years and develops between the roots of this tooth. As the premolar approaches, the roots resorb from their inner surfaces near the furcation.

Read on 24 October 2026. Sources: MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.); American Academy of Pediatric Dentistry, Management of the Developing Dentition and Occlusion in Pediatric Dentistry (2024 revision); American Dental Association, Tooth development charts (primary and permanent). Figures are usual values, and teeth vary from person to person.

Local anesthesia

Maxillary infiltration is routine for all teeth, and in children the thin, porous bone lets a buccal deposit diffuse to the pulp. Slow injection reduces discomfort.

The permanent successor is still developing beneath the tooth, so an intraligamentary injection, which places solution under pressure beside the root, carries a risk to the follicle. Buccal infiltration avoids it.

Read on 24 October 2026. Sources: MolarPath note Maxillary techniques, local anesthesia (built on Malamed's Handbook of Local Anesthesia, 7th ed.); 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

The pulp chamber is large for the size of the crown, and the pulp horns lie close to the dentinoenamel junction. The mesial horns are higher than the distal ones, and the mesiobuccal horn is the most prominent and the easiest to expose. About 4 mm of tooth structure separates a cusp tip from the roof of the chamber, so deep occlusal caries reaches the pulp early.

Primary molar roots are flat and usually hold several flat, ribbon-like canals that connect with one another, so complete debridement is not possible and pulpectomy depends heavily on irrigation. For a stainless steel crown, the buccal cervical ridge should be preserved to keep the crown retained.

Read on 24 October 2026. Sources: MolarPath note Pulp chambers and root canal morphology (built on Cohen's Pathways of the Pulp, 12th ed.); Chussid, Anatomy of Primary Teeth, Columbia University College of Dental Medicine lecture. 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); Kim and others, Root and Canal Morphology of Maxillary Primary Molar using CBCT and 3D CT, Journal of the Korean Academy of Pediatric Dentistry 2021; MolarPath note Primary tooth morphology (built on McDonald and Avery's Dentistry for the Child and Adolescent, 11th ed.). Figures are usual values, and teeth vary from person to person.