Upper first premolars – #12 and #5
The first of the two premolars on each side of the upper jaw, just behind the canines.
Roots
Usually two, but this depends a lot on the population: studies report two roots in anywhere from 7% to 96% of these teeth, and one root is more common in some Asian populations. Three roots are rare (under 7%).
Canals
Usually two. In a Saudi scan study, 75% had two canals at the tip of the root, 21% had one and 3% had three.
These are typical counts from scan studies. Teeth vary, and only an X-ray or scan shows what a particular tooth has.
When they come in
Usually at 10–11 years old, according to the ADA's eruption chart.
They replace the upper baby first molars, which fall out at 9–11 years.
They bite against the lower first premolars.
Sources
Wolf et al. 2025; Alqedairi et al. 2018; Martins et al. 2024; American Dental Association 2012; Harris 2005. Full titles are on the About page.