Tooth Number 19: Lower Left First Molar

Cavities, sealants and root canals on tooth 19

Cavities in the deep grooves. Children aged 6–11 without sealants have almost 3 times as many first-molar cavities as children with them.

Sealants. These thin coatings are painted on the chewing surfaces of back teeth. The CDC says they prevent 80% of cavities over 2 years in the back teeth, where 9 in 10 cavities occur.

The most treated tooth. In a survey of 3,350 patients at endodontic offices, the lower first molar was the tooth that most often needed a root canal (18.8% of treated teeth).

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.

Three or four canals. A review of 18,781 lower first molars found 3 canals in 61.3% and 4 in 35.7%. The front root held two canals in 94.4% of teeth. The back root had a single canal in 62.7%, so more than a third had a second canal there.

The same tooth on the right side, tooth 30, has its own section on crowns, fillings and implants.

Where is tooth 19?

Tooth 19 is in your lower jaw on your left side. It is the sixth tooth from the middle: start at the gap between the two bottom front teeth and count 6 teeth toward the back on your left side.

In a mirror, tooth 19 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 20, the lower left second premolar. Behind it is tooth 18, the lower left second molar. When it first comes in at about age 6, the tooth in front of it is usually still the baby second molar (tooth K), which the second premolar replaces years later.

Its mirror twin on the right side is tooth 30. The tooth in the same spot in the upper jaw is tooth 14, the upper left first molar.

Dental charts show the patient's right side on the left, so tooth 19 sits on the right half 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).

When does tooth 19 come in?

The lower first molars usually come in at 6–7 years according to the ADA chart. The AAPD chart gives 5.5–7 years.

In the ADA chart, they are among the first to come in, along with the upper first molars and the lower central incisors. In the AAPD's 13-step order, from the first molars (step 1) to the wisdom teeth (step 13), they are step 1.

Under the gum, according to the AAPD chart, it starts to harden (calcify) around birth, has a finished crown by 30–36 months and has a finished root by about 9–10 years, a few years after it comes into the mouth.

What does the lower first molar do?

Molars do the heavy grinding. Cleveland Clinic notes that about 90% of chewing happens on the molars. Molars have broad, flat chewing surfaces with 4–5 cusps (points) and the largest crowns of any teeth. The lower first molar is the largest tooth in the lower jaw, usually with five cusps.

It is also called the "6-year molar". First molars are named for the age they usually arrive, about 6 years.

Adult molars don't replace any baby tooth. They come in behind the baby teeth as the jaw grows.

How many roots does tooth 19 have?

2 roots, one at the front (mesial) and one at the back (distal). A review of 18,781 teeth found a third root in 13%, much more often in some ethnic groups.

Common problems with lower first molars

• Treatment. 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 19 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 19 in FDI and Palmer notation

There is no FDI tooth 19. In FDI the second digit only runs from 1 to 8, so 19 can only be a Universal number.

"36" can only be FDI. Universal numbers stop at 32, so a tooth 36 on any chart is this tooth.

Palmer needs the bracket. Every quarter of the mouth has a tooth 6 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:

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

Tools for tooth 19

• 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.
• Dental Numbness Calculator: lower molars usually get a nerve block, which lasts longer (about 3–3½ hours with lidocaine, vs about 2½ hours for a shot by the tooth).
• Dental Insurance Calculator: what your plan may pay for a crown or root canal.
• 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 Academy of Pediatric Dentistry. Dental Growth and Development (chronology after Logan & Kronfeld 1933, adapted 2003). Accessed October 26, 2026.
3. World Health Organization. Oral health surveys: basic methods, 5th edition (tooth notation after ISO 3950). 2013. Accessed October 26, 2026.
4. Nelson SJ. Elsevier. Wheeler's Dental Anatomy, Physiology and Occlusion, 11th edition. 2019.
5. American Dental Association. ADA Dental Claim Form (tooth designation systems). Accessed October 26, 2026.
6. Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Types of Teeth and their Functions. Accessed October 26, 2026.
7. Dentalcare.com (continuing education course CE500). An Overview of Dental Anatomy: Permanent Dentition. Accessed October 26, 2026.
8. Cleveland Clinic. Teeth: Anatomy, Types, Function & Care. last updated January 26, 2023. Accessed October 26, 2026.
9. Centers for Disease Control and Prevention. Dental Sealant Facts. May 15, 2024. Accessed October 26, 2026.
10. American Association of Endodontists. What is a Root Canal?. Accessed October 26, 2026.
11. U.S. FDA label via DailyMed (Dentsply). XYLOCAINE Dental (lidocaine HCl and epinephrine) injection. updated August 13, 2026. Accessed October 26, 2026.
12. de Pablo OV, Estevez R, Péix Sánchez M, Heilborn C, Cohenca N. Journal of Endodontics 36(12):1919–1931. Root anatomy and canal configuration of the permanent mandibular first molar: a systematic review. 2010. Accessed October 26, 2026.
13. Wayman BE, Patten JA, Dazey SE. Journal of Endodontics 20(8):399–401. Relative frequency of teeth needing endodontic treatment in 3350 consecutive endodontic patients. 1994. Accessed October 26, 2026.
14. Almadhoon HW, Abuiriban RW, Almassri H, Al-Hamed FS. Journal of Evidence-Based Dental Practice 22(2):101712. Efficacy of 4% articaine buccal infiltration versus inferior alveolar nerve block for mandibular molars with symptomatic irreversible pulpitis: a systematic review and meta-analysis. 2022. Accessed October 26, 2026.

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