When does tooth Q come in and fall out?
The lower baby lateral incisors usually come in at 10–16 months and fall out at 7–8 years (ADA). The AAPD chart gives 7–10 months to come in and 7–8 years to fall out.
In the ADA chart, they usually come in after the upper baby lateral incisors (9–13 months) and before the upper baby first molars (13–19 months), and they fall out at the same time as the upper baby lateral incisors, after the lower baby central incisors (6–7 years) and before the upper baby first molars (9–11 years).
Tooth Q is replaced by tooth 26, the lower right lateral incisor, which usually comes in at 7–8 years (ADA). Under the gum, tooth Q starts to harden in the 4th month of pregnancy and is fully formed by about 18–24 months (AAPD).
Crowding when tooth Q is replaced
Early crowding often eases. A review cited by the AAPD found that crowding of the lower front teeth in the mixed-teeth years tended to decrease over time, and the more crowding there was, the more it improved on its own. Some children's crowding got worse, though.
To help crowded adult lateral incisors (tooth 26) line up, dentists may slim the sides of the baby canines next to them.
The same tooth on the left side, tooth N, has its own section on teething, late teeth and early care.
Where is tooth Q?
Tooth Q is in your child's lower jaw on their right side. It is the second tooth from the middle: start at the gap between the two bottom front teeth and count 2 teeth toward the back on their right side.
"Left" and "right" always mean the child's own sides, so when you face your child, tooth Q is on your left.
In front of it (toward the middle) is tooth P, the lower right baby central incisor. Behind it is tooth R, the lower right baby canine.
Its mirror twin on the left side is tooth N. The tooth in the same spot in the upper jaw is tooth D, the upper right baby lateral incisor.
Dental charts show the patient's right side on the left, so tooth Q sits on the left half of the bottom row. Lower right teeth finish the circle, from P (the front tooth) to T (the back molar).
What does the lower baby lateral incisor do?
Baby incisors are the front teeth young children use to bite and cut soft food. 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 Q have?
One small root, which dissolves as the adult tooth grows underneath.
Common problems with lower baby lateral incisors
- Injuries. Worldwide, about 1 in 5 children (22.7%) injure at least one baby tooth. In baby teeth the most common injury is a tooth pushed out of position (a luxation) rather than a broken tooth.
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 Q in FDI and Palmer notation
| System | Tooth Q is written | What it means |
|---|---|---|
| Universal (ADA, used in the US) | Q | Baby teeth are lettered A–T around the mouth, starting at the upper right back molar. |
| FDI / ISO 3950 (international) | 82 | First digit 8 = lower right quarter (baby teeth use 5–8); second digit 2 = second baby tooth from the middle. Said "eight-two". |
| Palmer | B┐ (often typed LRB) | The ┐ bracket marks the lower right quarter; B = second baby tooth from the middle. |
Palmer stops at E. Palmer letters only run from A to E in each quarter, so a "Q" can only be a Universal letter.
FDI baby teeth start with 5 to 8. The first digit 8 marks the lower right baby quarter, so FDI 82 can't be mixed up with an adult tooth.
Letters and numbers don't line up. Q is letter 17 of the alphabet, but baby tooth Q is replaced by adult tooth 26, not tooth 17.
All baby teeth in the lower right quarter
From the front of the mouth to the back:
| Universal | FDI | Palmer | Tooth |
|---|---|---|---|
| P | 81 | A┐ (LRA) | Baby central incisor |
| Q | 82 | B┐ (LRB) | Baby lateral incisor (this tooth) |
| R | 83 | C┐ (LRC) | Baby canine |
| S | 84 | D┐ (LRD) | Baby first molar |
| T | 85 | E┐ (LRE) | Baby second molar |
The Tooth Number Chart & Converter converts any tooth between the three systems.
Tools for tooth Q
- 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 Q?
When does tooth Q come in?
When does tooth Q fall out?
Will the adult tooth that replaces tooth Q come in crowded?
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.
- Levin L et al. (International Association of Dental Traumatology). Dental Traumatology 36(4):309–313. IADT guidelines for the management of traumatic dental injuries: General introduction. 2020. Accessed October 26, 2026.
- Petti S, Glendor U, Andersson L. Dental Traumatology 34(2):71–86. World traumatic dental injury prevalence and incidence, a meta-analysis. 2018. Accessed October 26, 2026.
Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.