Tartar and crowding on tooth 24
Tartar. Hard tartar (calculus) builds up most easily on the tongue side of the six lower front teeth. Brushing and flossing behind these teeth, and regular cleanings, help keep it under control.
Crowding can come back. The AAPD notes that lower incisors have a high rate of relapse into crowding and twisting after they are straightened, and that the jaws keep changing with age, which adds more crowding.
The same tooth on the right side, tooth 25, has its own section on adult teeth that come in behind baby teeth.
Where is tooth 24?
Tooth 24 is one of the two bottom front teeth right in the middle of your mouth: the one on your left side.
In a mirror, tooth 24 shows on the left side of your reflection. Someone looking into your mouth sees it on their right.
Right next to it, across the middle, is tooth 25, the other lower central incisor. Behind it is tooth 23, the lower left lateral incisor.
Its mirror twin on the right side is tooth 25. The tooth in the same spot in the upper jaw is tooth 9, the upper left central incisor.
Dental charts show the patient's right side on the left, so tooth 24 sits just right of the center line of the bottom row. The numbers then drop to the lower jaw: lower left teeth run from 17 (the wisdom tooth) to 24 (the front tooth).
What does the lower central incisor do?
Incisors have a thin, straight biting edge for cutting into food. They are the most visible teeth in the mouth. The lower central incisors are the smallest teeth in the adult mouth and the smallest of all the incisors.
Common problems with lower central incisors
- Cavities and chips. Small cavities are fixed with a filling. If decay or an injury reaches the nerve, root canal treatment can save the tooth, often followed by a crown.
If tooth 24 hurts, feels loose, or the gum around it swells, the Dental Emergency Checker can help you decide how soon to see a dentist. Swelling that spreads to the eye or neck, or makes it hard to breathe or swallow, is an emergency: call 911. These are typical problems for this kind of tooth, not a diagnosis.
When does tooth 24 come in?
Both the ADA and AAPD charts give 6–7 years for the lower central incisors.
Tooth 24 replaces the lower left baby central incisor (tooth O), which usually falls out at 6–7 years (ADA).
In the ADA chart, they are among the first to come in, along with the upper first molars and the lower first molars. In the AAPD's 13-step order, from the first molars (step 1) to the wisdom teeth (step 13), they are step 2.
Under the gum, according to the AAPD chart, it starts to harden (calcify) at about 3–4 months, has a finished crown by 4–5 years and has a finished root by about 9–10 years, a few years after it comes into the mouth.
How many roots does tooth 24 have?
One narrow root, flattened from side to side.
Tooth 24 in FDI and Palmer notation
| System | Tooth 24 is written | What it means |
|---|---|---|
| Universal (ADA, used in the US) | 24 | Adult teeth are numbered 1–32 around the mouth, starting at the upper right wisdom tooth. |
| FDI / ISO 3950 (international) | 31 | First digit 3 = lower left quarter; second digit 1 = first tooth from the middle. Said "three-one". |
| Palmer | ┌1 (often typed LL1) | The ┌ bracket marks the lower left quarter; 1 = first tooth from the middle. |
"24" in FDI is a different tooth. Read as an FDI code, 24 means the upper left first premolar (tooth 12 in Universal). Charts and X-ray reports from outside the US often use FDI, so check which system is in use.
On a US chart, "31" is a different tooth. Universal 31 is the lower right second molar (tooth 31), so "tooth 31" only means this tooth when the chart uses FDI.
Palmer needs the bracket. Every quarter of the mouth has a tooth 1 in Palmer notation; only the ┌ (or the letters LL) makes it this one.
All adult teeth in the lower left quarter
From the front of the mouth to the back:
| Universal | FDI | Palmer | Tooth |
|---|---|---|---|
| 24 | 31 | ┌1 (LL1) | Central incisor (this tooth) |
| 23 | 32 | ┌2 (LL2) | Lateral incisor |
| 22 | 33 | ┌3 (LL3) | Canine |
| 21 | 34 | ┌4 (LL4) | First premolar |
| 20 | 35 | ┌5 (LL5) | Second premolar |
| 19 | 36 | ┌6 (LL6) | First molar |
| 18 | 37 | ┌7 (LL7) | Second molar |
| 17 | 38 | ┌8 (LL8) | Wisdom tooth |
The Tooth Number Chart & Converter converts any tooth between the three systems.
Tools for tooth 24
- Adult Teeth Predictor: likely dates for your child's adult teeth.
- Dental Emergency Checker: how soon to see a dentist if it hurts or breaks.
- Knocked-Out Tooth Rescue: first aid for a knocked-out adult tooth.
- How Long Does Dental Work Last?: how long fillings, crowns, veneers and implants usually last, from long-term studies.
- Dental Treatment Plan Decoder: plain English for treatment-plan shorthand like "#30 MOD comp".
Frequently asked questions
What tooth is number 24?
Is tooth 24 the same as tooth 31?
At what age does tooth 24 come in?
Why does tartar build up behind tooth 24?
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.
- Cleveland Clinic. Teeth: Anatomy, Types, Function & Care. last updated January 26, 2023. Accessed October 26, 2026.
- Dawes C. Journal of the Canadian Dental Association 72(10):923–926. Why does supragingival calculus form preferentially on the lingual surface of the 6 lower anterior teeth?. 2006. Accessed October 26, 2026.
Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.