Baby tooth O is the lower left central incisor in the baby (primary) teeth. In the FDI (ISO 3950) system it is 71, and in Palmer notation it is ┌A. It usually comes in at 6-10 mos and falls out at 6-7 yrs.
Tooth O at a glance
| Universal (US) | O |
| FDI / ISO 3950 | 71 |
| Palmer | ┌A |
| Name | Lower left central incisor |
| Type | Central incisor (baby tooth) |
| Jaw | Lower (mandible) |
| Side | Patient’s left |
| Comes in | 6-10 mos |
| Falls out | 6-7 yrs |
| Roots | 1 |
| Root canals (usual) | 1 |
| Chewing surface | An incisal edge |
Where it is and what it does
It sits in the lower jaw on the patient’s left side, right at the front, next to the midline. Baby incisors bite into food and help children learn to make sounds such as “th”, “f” and “s”.
Neighbouring and related teeth
- Across the midline: Baby tooth P, the lower right central incisor
- Behind it: Baby tooth N, the lower left lateral incisor
- The matching tooth in the upper jaw: Baby tooth F
- Replaced by: Tooth number 24, the lower left central incisor
Common dental work on this tooth
Baby front teeth can be affected by early childhood tooth decay and by knocks and falls. A dentist may treat decay with a filling or, if a tooth is badly damaged, remove it.
Questions
What tooth is letter O?
Baby tooth O is the lower left central incisor (a baby tooth). Letters A to T are used for baby teeth in the Universal system used in the United States.
What is baby tooth O in the FDI and Palmer systems?
In FDI it is 71, said digit by digit (“seven-one”). The first digit is the quadrant and the second is the position from the midline. In Palmer notation it is ┌A.
When does baby tooth O fall out?
Usually at about 6-7 yrs, when the adult lower left central incisor pushes it out from underneath. It first comes in at about 6-10 mos.
For education only. This is not dental advice; your dentist can tell you what is right for your own teeth.