Tooth Number 26: Lower Right Lateral Incisor

Root canal on tooth 26

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.

A hidden second canal. Lower incisors look simple, but a review of 71,404 lower front teeth from 26 countries found second canals more often in lateral incisors than in central incisors. Canal shapes also varied by ethnicity, so dentists study the X-rays closely before treatment.

The same tooth on the left side, tooth 23, has its own section on making room when it comes in crowded.

Where is tooth 26?

Tooth 26 is in your lower jaw on your 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 your right side.

In a mirror, tooth 26 shows on the right side of your reflection. Someone looking into your mouth sees it on their left.

In front of it (toward the middle) is tooth 25, the lower right central incisor. Behind it is tooth 27, the lower right canine.

Its mirror twin on the left side is tooth 23. The tooth in the same spot in the upper jaw is tooth 7, the upper right lateral incisor.

Dental charts show the patient's right side on the left, so tooth 26 sits on the left half of the bottom row. Lower right teeth finish the circle, from 25 (the front tooth) to 32 (the wisdom tooth).

What does the lower lateral incisor do?

Incisors have a thin, straight biting edge for cutting into food. They are the most visible teeth in the mouth. Lower lateral incisors are slightly wider than the lower central incisors beside them, but still among the smallest adult teeth.

Common problems with lower lateral incisors

• 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.
• 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 26 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 26 come in?

Both the ADA and AAPD charts give 7–8 years for the lower lateral incisors.

Tooth 26 replaces the lower right baby lateral incisor (tooth Q), which usually falls out at 7–8 years (ADA).

In the ADA chart, they come in at the same time as the upper central incisors, after the lower central incisors (6–7 years) and before the upper lateral incisors (8–9 years). In the AAPD's 13-step order, from the first molars (step 1) to the wisdom teeth (step 13), they are step 4.

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 10 years, a few years after it comes into the mouth.

How many roots does tooth 26 have?

One narrow root.

Tooth 26 in FDI and Palmer notation

"26" in FDI is a different tooth. Read as an FDI code, 26 means the upper left first molar (tooth 14 in Universal). Charts and X-ray reports from outside the US often use FDI, so check which system is in use.

"42" can only be FDI. Universal numbers stop at 32, so a tooth 42 on any chart is this tooth.

Palmer needs the bracket. Every quarter of the mouth has a tooth 2 in Palmer notation; only the ┐ (or the letters LR) makes it this one.

All adult 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 26

• 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

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. World Health Organization. Oral health surveys: basic methods, 5th edition (tooth notation after ISO 3950). 2013. Accessed October 26, 2026.
5. Nelson SJ. Elsevier. Wheeler's Dental Anatomy, Physiology and Occlusion, 11th edition. 2019.
6. American Dental Association. ADA Dental Claim Form (tooth designation systems). Accessed October 26, 2026.
7. Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Types of Teeth and their Functions. Accessed October 26, 2026.
8. Cleveland Clinic. Teeth: Anatomy, Types, Function & Care. last updated January 26, 2023. Accessed October 26, 2026.
9. American Association of Endodontists. What is a Root Canal?. Accessed October 26, 2026.
10. 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.
11. Dhuldhoya DN et al. Journal of Conservative Dentistry 25(3):226–240. Root canal anatomy of human permanent mandibular incisors and mandibular canines: A systematic review. 2022. Accessed October 26, 2026.

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