Tooth Letter B: Upper Right Baby First Molar

When does tooth B come in and fall out?

The upper baby first molars usually come in at 13–19 months and fall out at 9–11 years (ADA). The AAPD chart gives 11–18 months to come in and 9–11 years to fall out.

In the ADA chart, they usually come in after the lower baby lateral incisors (10–16 months) and before the lower baby first molars (14–18 months), and they fall out at the same time as the lower baby first molars, after the lower baby lateral incisors (7–8 years) and before the lower baby canines (9–12 years).

Tooth B is replaced by tooth 5, the upper right first premolar, which usually comes in at 10–11 years (ADA). Under the gum, tooth B starts to harden in the 4th month of pregnancy and is fully formed by about 24–30 months (AAPD).

Tooth B sinking below its neighbors

Fused to the bone. Baby molars are the teeth most likely to fuse to the jawbone (ankylosis), which the AAPD reports in 7% to 14% of children. A fused tooth stops moving and can look like it is sinking as the teeth around it keep growing.

A sinking baby molar can let the teeth beside it tip into the space. A review found that keeping the tooth may work long term when the sinking is mild or moderate, less than half of its root has dissolved, and it has no decay or filling.

Losing it early. If a baby tooth is lost early to decay or injury, nearby teeth can drift into the room the adult tooth needs. Dentists sometimes fit a space maintainer, though the AAPD notes the evidence on how well they prevent crowding is limited.

The same tooth on the left side, tooth I, has its own section on decay between baby molars.

Where is tooth B?

Tooth B is in your child's upper jaw on their right side. It is the fourth tooth from the middle: start at the gap between the two top front teeth and count 4 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 B is on your left.

In front of it (toward the middle) is tooth C, the upper right baby canine. Behind it is tooth A, the upper right baby second molar.

Its mirror twin on the left side is tooth I. The tooth in the same spot in the lower jaw is tooth S, the lower right baby first molar.

Dental charts show the patient's right side on the left, so tooth B sits on the left half of the top row. Baby teeth use letters in the same path as adult numbers: upper right teeth run from A (the back molar) to E (the front tooth).

What does the upper baby first molar do?

Baby molars do the grinding for young children, and they keep room for the premolars that replace them. 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.

Adult premolars replace the baby molars, so this tooth is followed by the upper first premolar, not by a molar.

How many roots does tooth B have?

3 roots. Baby molar roots are thin and spread wide apart. The premolar that will replace the baby molar forms in the space between them.

When to call a dentist about tooth B

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.

Tooth B in FDI and Palmer notation

Palmer letters mean something else. In Palmer notation the letters A–E count out from the middle in each quarter, so a Palmer "B" is always a baby lateral incisor, not this tooth. In Palmer, tooth B is D┘ (URD).

FDI baby teeth start with 5 to 8. The first digit 5 marks the upper right baby quarter, so FDI 54 can't be mixed up with an adult tooth.

Letters and numbers don't line up. B is letter 2 of the alphabet, but baby tooth B is replaced by adult tooth 5, not tooth 2.

All baby teeth in the upper right quarter

From the front of the mouth to the back:

The Tooth Number Chart & Converter converts any tooth between the three systems.

Tools for tooth B

• 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

Sources

1. American Dental Association (MouthHealthy). Permanent Tooth Development (eruption chart). 2012. Accessed October 26, 2026.
2. American Dental Association (MouthHealthy). Primary Tooth Development (eruption chart). 2012. Accessed October 26, 2026.
3. American Academy of Pediatric Dentistry. Dental Growth and Development (chronology after Logan & Kronfeld 1933, adapted 2003). Accessed October 26, 2026.
4. 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.
5. World Health Organization. Oral health surveys: basic methods, 5th edition (tooth notation after ISO 3950). 2013. Accessed October 26, 2026.
6. Nelson SJ. Elsevier. Wheeler's Dental Anatomy, Physiology and Occlusion, 11th edition. 2019.
7. American Dental Association. ADA Dental Claim Form (tooth designation systems). Accessed October 26, 2026.
8. Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Types of Teeth and their Functions. Accessed October 26, 2026.
9. Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Permanent Dentition. Accessed October 26, 2026.
10. American Dental Association (MouthHealthy). Tooth Decay with Baby Bottles. Accessed October 26, 2026.
11. Patano A et al. Children (Basel) 10(3):582. Therapeutic Strategies of Primary Molar Infraocclusion: A Systematic Review. 2023. Accessed October 26, 2026.

Last reviewed October 26, 2026 by the Dental Health Time editorial team, against the sources above. How we review.