When does tooth M come in and fall out?
The lower baby canines usually come in at 17–23 months and fall out at 9–12 years (ADA). The AAPD chart gives 16–20 months to come in and 9–11 years to fall out.
In the ADA chart, they usually come in after the upper baby canines (16–22 months) and before the lower baby second molars (23–31 months), and they usually fall out after the lower baby first molars (9–11 years) and before the upper baby second molars (10–12 years).
Tooth M is replaced by tooth 22, the lower left canine, which usually comes in at 9–10 years (ADA). Under the gum, tooth M starts to harden in the 4th month of pregnancy and is fully formed by about 30–39 months (AAPD).
Removing tooth M to make room
When the lower adult incisors come in crowded, dentists sometimes slim the sides of the lower baby canines or remove them early to make room. A holding wire (passive lingual arch) may then be fitted to save space for the adult teeth behind.
A trade-off. Removing the lower baby canines straightens the incisors, but it can cost up to 2.7 mm of arch length, so dentists weigh one against the other.
The same tooth on the right side, tooth R, has its own section on what happens when one is lost early.
Where is tooth M?
Tooth M is in your child's lower jaw on their left side. It is the third tooth from the middle: start at the gap between the two bottom front teeth and count 3 teeth toward the back on their left side.
"Left" and "right" always mean the child's own sides, so when you face your child, tooth M is on your right.
In front of it (toward the middle) is tooth N, the lower left baby lateral incisor. Behind it is tooth L, the lower left baby first molar.
Its mirror twin on the right side is tooth R. The tooth in the same spot in the upper jaw is tooth H, the upper left baby canine.
Dental charts show the patient's right side on the left, so tooth M sits on the right half of the bottom row. The letters then drop to the lower jaw: lower left teeth run from K (the back molar) to O (the front tooth).
What does the lower baby canine do?
Baby canines are pointed teeth that help tear food and keep room for the adult canines. Baby teeth matter even though they fall out: children need them to chew, speak and smile, and they help the adult teeth come in correctly.
How many roots does tooth M have?
One root.
Common problems with lower baby canines
- Cavities. The AAPD advises repairing decayed baby teeth when possible, rebuilding each tooth to its original shape so it keeps its place until the adult tooth is ready.
If a baby tooth is knocked loose or out in a fall, or your child has swelling, fever or pain, call your dentist. Never put a knocked-out baby tooth back in (Knocked-Out Tooth Rescue explains why). Swelling that makes it hard to breathe or swallow is an emergency: call 911. These are typical problems for this kind of tooth, not a diagnosis.
Tooth M in FDI and Palmer notation
| System | Tooth M is written | What it means |
|---|---|---|
| Universal (ADA, used in the US) | M | Baby teeth are lettered A–T around the mouth, starting at the upper right back molar. |
| FDI / ISO 3950 (international) | 73 | First digit 7 = lower left quarter (baby teeth use 5–8); second digit 3 = third baby tooth from the middle. Said "seven-three". |
| Palmer | ┌C (often typed LLC) | The ┌ bracket marks the lower left quarter; C = third baby tooth from the middle. |
Palmer stops at E. Palmer letters only run from A to E in each quarter, so an "M" can only be a Universal letter.
FDI baby teeth start with 5 to 8. The first digit 7 marks the lower left baby quarter, so FDI 73 can't be mixed up with an adult tooth.
Letters and numbers don't line up. M is letter 13 of the alphabet, but baby tooth M is replaced by adult tooth 22, not tooth 13.
All baby teeth in the lower left quarter
From the front of the mouth to the back:
| Universal | FDI | Palmer | Tooth |
|---|---|---|---|
| O | 71 | ┌A (LLA) | Baby central incisor |
| N | 72 | ┌B (LLB) | Baby lateral incisor |
| M | 73 | ┌C (LLC) | Baby canine (this tooth) |
| L | 74 | ┌D (LLD) | Baby first molar |
| K | 75 | ┌E (LLE) | Baby second molar |
The Tooth Number Chart & Converter converts any tooth between the three systems.
Tools for tooth M
- Teething Calculator: which baby teeth are due at your baby's age.
- Baby Teeth Tracker: log each tooth in and out.
- Kids Fluoride Calculator: how much toothpaste to use; the ADA says a rice-grain smear until age 3, then a pea-size amount.
- Tooth Fairy Calculator: what families give for a lost tooth.
- Dental Treatment Plan Decoder: plain English for treatment-plan shorthand like "#30 MOD comp".
Frequently asked questions
What tooth is letter M?
When does tooth M come in?
When does tooth M fall out?
Why would a dentist remove tooth M early?
Sources
- American Dental Association (MouthHealthy). Permanent Tooth Development (eruption chart). 2012. Accessed October 26, 2026.
- American Dental Association (MouthHealthy). Primary Tooth Development (eruption chart). 2012. Accessed October 26, 2026.
- American Academy of Pediatric Dentistry. Dental Growth and Development (chronology after Logan & Kronfeld 1933, adapted 2003). Accessed October 26, 2026.
- American Academy of Pediatric Dentistry. Management of the Developing Dentition and Occlusion in Pediatric Dentistry (Reference Manual of Pediatric Dentistry). latest revision 2024. Accessed October 26, 2026.
- World Health Organization. Oral health surveys: basic methods, 5th edition (tooth notation after ISO 3950). 2013. Accessed October 26, 2026.
- Nelson SJ. Elsevier. Wheeler's Dental Anatomy, Physiology and Occlusion, 11th edition. 2019.
- American Dental Association. ADA Dental Claim Form (tooth designation systems). Accessed October 26, 2026.
- Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Types of Teeth and their Functions. Accessed October 26, 2026.
- American Dental Association (MouthHealthy). Tooth Decay with Baby Bottles. Accessed October 26, 2026.
Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.