Tooth Letter S: Lower Right Baby First Molar

When does tooth S come in and fall out?

The lower baby first molars usually come in at 14–18 months and fall out at 9–11 years (ADA). The AAPD chart gives 11–18 months to come in and 10–12 years to fall out.

In the ADA chart, they usually come in after the upper baby first molars (13–19 months) and before the upper baby canines (16–22 months), and they fall out at the same time as the upper baby first molars, after the lower baby lateral incisors (7–8 years) and before the lower baby canines (9–12 years).

Tooth S is replaced by tooth 28, the lower right first premolar, which usually comes in at 10–12 years (ADA). Under the gum, tooth S starts to harden in the 4th month of pregnancy and is fully formed by about 24–30 months (AAPD).

Crowns for a decayed tooth S

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.

Crowns for baby molars. Preformed crowns, usually stainless steel, are recommended for baby molars that are very decayed, badly broken down or have had nerve treatment. In a Cochrane review, crowns were less likely than fillings to fail badly or cause pain over the long term.

The Hall Technique. With this method, the metal crown is pushed onto the tooth without a numbing shot, drilling or decay removal. The review found it likely causes less discomfort than a filling.

For a better look, crowns also come with a white veneer, or made wholly of white ceramic.

The same tooth on the left side, tooth L, has its own section on space maintainers after early loss.

Where is tooth S?

Tooth S is in your child's lower jaw on their right side. It is the fourth tooth from the middle: start at the gap between the two bottom 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 S is on your left.

In front of it (toward the middle) is tooth R, the lower right baby canine. Behind it is tooth T, the lower right baby second molar.

Its mirror twin on the left side is tooth L. The tooth in the same spot in the upper jaw is tooth B, the upper right baby first molar.

Dental charts show the patient's right side on the left, so tooth S 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 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.

How many roots does tooth S have?

2 roots, one at the front and one at the back. 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 S

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 S in FDI and Palmer notation

Palmer stops at E. Palmer letters only run from A to E in each quarter, so an "S" 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 84 can't be mixed up with an adult tooth.

Letters and numbers don't line up. S is letter 19 of the alphabet, but baby tooth S is replaced by adult tooth 28, not tooth 19.

All baby teeth in the lower 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 S

• 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. American Dental Association (MouthHealthy). Tooth Decay with Baby Bottles. Accessed October 26, 2026.
10. Innes NP et al. Cochrane Database of Systematic Reviews, CD005512. Preformed crowns for decayed primary molar teeth. 2015. Accessed October 26, 2026.

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