Root canal on tooth 13
What it involves. Root canal treatment removes inflamed or infected pulp from inside the tooth, then cleans, disinfects, fills and seals it. It can usually be done in one or two visits, and the tooth is then restored with a crown or filling.
One root, but often two canals. In a CBCT study of 1,118 upper second premolars, 94% had one root, but only 55% had a single canal.
Close to the sinus. In the same study, the root tips of single-rooted teeth sat on average about 2.5 mm below the floor of the sinus. Overall, roots sat farther from the sinus in older people.
Sinus link. The roots of upper back teeth can reach up into the maxillary sinus, with only a thin layer of tissue between them. Because of that, a long-lasting infection at the root tip can sometimes spread into the sinus (odontogenic sinusitis).
Left and right usually match: root and canal numbers were the same on both sides in about 82% of upper second premolar pairs in another CBCT study.
The same tooth on the right side, tooth 4, has its own section on a second premolar that never formed.
Where is tooth 13?
Tooth 13 is in your upper jaw on your left side. It is the fifth tooth from the middle: start at the gap between the two top front teeth and count 5 teeth toward the back on your left side.
In a mirror, tooth 13 shows on the left side of your reflection. Someone looking into your mouth sees it on their right.
In front of it (toward the middle) is tooth 12, the upper left first premolar. Behind it is tooth 14, the upper left first molar.
Its mirror twin on the right side is tooth 4. The tooth in the same spot in the lower jaw is tooth 20, the lower left second premolar.
Dental charts show the patient's right side on the left, so tooth 13 sits on the right half of the top row. Universal numbers continue across the top: upper left teeth run from 9 (the front tooth) to 16 (the wisdom tooth).
What does the upper second premolar do?
Premolars (also called bicuspids) sit between the canines and the molars and help crush and grind food. They have features of both their neighbors. The upper second premolar looks a lot like the first premolar beside it, but it usually has just one root.
It is also called the "second bicuspid".
Adult premolars replace the baby molars. There are no premolars among the 20 baby teeth.
How many roots does tooth 13 have?
Usually 1 root, sometimes 2.
When does tooth 13 come in?
Both the ADA and AAPD charts give 10–12 years for the upper second premolars.
Tooth 13 replaces the upper left baby second molar (tooth J), which usually falls out at 10–12 years (ADA).
In the ADA chart, they come in at the same time as the lower first premolars, after the upper first premolars (10–11 years) and before the upper canines (11–12 years). In the AAPD's 13-step order, from the first molars (step 1) to the wisdom teeth (step 13), they are step 9.
Under the gum, according to the AAPD chart, it starts to harden (calcify) at about 24–30 months, has a finished crown by 6–7 years and has a finished root by about 12–14 years, a few years after it comes into the mouth.
Common problems with upper second premolars
- Cavities in the grooves and between the teeth. 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 13 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.
Tooth 13 in FDI and Palmer notation
| System | Tooth 13 is written | What it means |
|---|---|---|
| Universal (ADA, used in the US) | 13 | Adult teeth are numbered 1–32 around the mouth, starting at the upper right wisdom tooth. |
| FDI / ISO 3950 (international) | 25 | First digit 2 = upper left quarter; second digit 5 = fifth tooth from the middle. Said "two-five". |
| Palmer | └5 (often typed UL5) | The └ bracket marks the upper left quarter; 5 = fifth tooth from the middle. |
"13" in FDI is a different tooth. Read as an FDI code, 13 means the upper right canine (tooth 6 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, "25" is a different tooth. Universal 25 is the lower right central incisor (tooth 25), so "tooth 25" only means this tooth when the chart uses FDI.
Palmer needs the bracket. Every quarter of the mouth has a tooth 5 in Palmer notation; only the └ (or the letters UL) makes it this one.
All adult teeth in the upper left quarter
From the front of the mouth to the back:
| Universal | FDI | Palmer | Tooth |
|---|---|---|---|
| 9 | 21 | └1 (UL1) | Central incisor |
| 10 | 22 | └2 (UL2) | Lateral incisor |
| 11 | 23 | └3 (UL3) | Canine |
| 12 | 24 | └4 (UL4) | First premolar |
| 13 | 25 | └5 (UL5) | Second premolar (this tooth) |
| 14 | 26 | └6 (UL6) | First molar |
| 15 | 27 | └7 (UL7) | Second molar |
| 16 | 28 | └8 (UL8) | Wisdom tooth |
The Tooth Number Chart & Converter converts any tooth between the three systems.
Tools for tooth 13
- Dental Emergency Checker: how soon to see a dentist if it hurts or breaks.
- Dental Numbness Calculator: how long numbness lasts after a filling.
- Dental Insurance Calculator: what your plan may pay for a crown or root canal.
- Adult Teeth Predictor: likely dates for your child's adult teeth.
- 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 13?
Is tooth 13 the same as tooth 25?
At what age does tooth 13 come in?
How many canals does tooth 13 have?
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.
- 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.
- Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Permanent Dentition. Accessed October 26, 2026.
- Cleveland Clinic. Teeth: Anatomy, Types, Function & Care. last updated January 26, 2023. Accessed October 26, 2026.
- American Association of Endodontists. What is a Root Canal?. Accessed October 26, 2026.
- Ordinola-Zapata R, Azevedo B, Tataryn RW, Versiani MA. Otolaryngologic Clinics of North America 57(6):927–939. Maxillary Dental Anatomy and Physiology: Endodontic and Periodontal. 2024. Accessed October 26, 2026.
- Yan Y, Li J, Zhu H, Liu J, Ren J, Zou L. BMC Oral Health 21:358. CBCT evaluation of root canal morphology and anatomical relationship of root of maxillary second premolar to maxillary sinus in a western Chinese population. 2021. Accessed October 26, 2026.
- Li YH et al. Archives of Oral Biology 94:84–92. Symmetry of root anatomy and root canal morphology in maxillary premolars analyzed using cone-beam computed tomography. 2018. Accessed October 26, 2026.
Last reviewed by the Dental Health Time editorial team, against the sources above. How we review.