Tooth number 20 is the lower left second premolar, a permanent (adult) tooth. In the FDI (ISO 3950) system it is 35, and in Palmer notation it is ┌5.
Tooth #20 at a glance
| Universal (US) | 20 |
| FDI / ISO 3950 | 35 |
| Palmer | ┌5 |
| Name | Lower left second premolar |
| Type | Second premolar (adult tooth) |
| Jaw | Lower (mandible) |
| Side | Patient’s left |
| Comes in | 11-12 yrs |
| Roots | 1 |
| Root canals (usual) | 1 |
| Chewing surface | 2 or 3 cusps |
Where it is and what it does
It sits in the lower jaw on the patient’s left side, fifth from the midline. Premolars (also called bicuspids) crush and tear food. They sit between the canines and the molars and share the work of both.
Neighbouring and related teeth
- In front of it (toward the midline): Tooth number 21, the lower left first premolar
- Behind it: Tooth number 19, the lower left first molar
- Same tooth on the other side: Tooth number 29
- The matching tooth in the upper jaw: Tooth number 13
- Replaces: Baby tooth K, the baby lower left second molar
Common dental work on this tooth
Premolars commonly get fillings. First premolars are also the teeth most often removed to make space for orthodontic treatment (braces).
Questions
What tooth is number 20?
Tooth number 20 is the lower left second premolar. Numbers 1 to 32 are used for adult teeth in the Universal system used in the United States, starting with the upper right wisdom tooth.
What is tooth number 20 in the FDI and Palmer systems?
In FDI it is 35, said digit by digit (“three-five”). The first digit is the quadrant and the second is the position from the midline. In Palmer notation it is ┌5.
When does tooth 20 come in?
Usually at about 11-12 yrs. Timing varies from person to person.
For education only. This is not dental advice; your dentist can tell you what is right for your own teeth.