Tooth #21 – Lower left first premolar
4th tooth back from the middle, lower left.
- International
- 34
- Palmer
- 4
- Type
- Premolar
- Roots
- 1
- Canals
- usually 1
- Comes in
- 10–12 years
The first of the two smaller back teeth (premolars) on the lower left, just behind the canine.
- In front: #22 lower left canine
- Behind: #20 lower left second premolar
- Same tooth on the other side: #28 lower right first premolar
- Bites against: #12 upper left first premolar
It replaces the lower left baby first molar (L), which falls out at 9–11 years.
Usually one root (1–3) and usually one canal (1–3).
Lower first premolars: roots, canals and the studies behind the counts →
This tooth is #21 in the US and 34 in the international (FDI) system, where the 3 means the lower left quarter and the 4 is its place counting from the front.
In the international system, 21 is the upper left central incisor (#9).
American Dental Association 2024; Harris 2005; American Dental Association 2012. Full titles are on the About page.