Tooth 30: Your Lower Right First Molar

Reviewed by the toothcheck Dental Team Independent dentist providing online second opinions.

Tooth 30 is your lower right first molar — the big, flat-topped grinding tooth partway back on the bottom right side of your mouth. A treatment plan listing "30" or "#30" means this tooth.

Worth settling immediately: right means your right, not the right of someone facing you. Tooth 30 sits on the same side as your right hand. Because X-rays are conventionally displayed as though you are facing the patient, tooth 30 appears on the left-hand side of the image — the opposite of where people instinctively look.

Where Tooth 30 Sits

Counting backwards along your lower right side:

Tooth 30 has the second premolar (29) directly in front of it and the second molar (31) directly behind. Counting forward from the very back of your mouth it is the third tooth — or the second, if the wisdom tooth was removed or never came through.

Tooth 30 is the mirror image of tooth 19 on the other side of your lower jaw. The two are anatomically near-identical, which is why they are so often discussed together.

What the Number 30 Actually Means

Dentists in the United States use the Universal Numbering System, the standard underpinning the American Dental Association procedure codes. It numbers the 32 adult teeth 1 to 32 in one continuous loop:

• 1 is the upper right wisdom tooth
• the count runs across the top to 16 at the upper left
• drops to 17, the lower left wisdom tooth
• and runs back across the bottom to 32, the lower right wisdom tooth

Because the bottom row is counted from left to right, the high numbers land on your lower right. Tooth 30 is third from the end of that run.

The same tooth is labelled differently in other systems:

Records showing a two-digit number like 46 are describing this tooth. Our guide to Universal vs FDI tooth numbering explains the conversion.

Why Tooth 30 Is One of the Most Treated Teeth

Lower first molars are repaired more often than most teeth in the mouth, for reasons that come down to timing and workload:

• It erupts around age six, ahead of nearly every other permanent tooth, giving it the longest exposure to decay. Hence the common name, the six-year molar.
• It takes a large share of chewing force, so wear, cracks and fractures show up here first.
• Its biting surface has deep grooves that hold food and resist a toothbrush, and it sits far enough back that brushing tends to be less thorough.
• No baby tooth is shed to make room for it. It erupts behind the baby teeth already present, so its arrival is easy to miss — and it often misses the sealant window as a result.

Anatomically tooth 30 usually has two roots and most commonly three canals, the same as its counterpart on the left. If a root canal is proposed, the number of canals is one of the factors driving both the difficulty and the fee.

Finding Tooth 30 on Your Own X-Ray

1. Work out the side. Films are displayed as though you are facing the patient, so the patient's right sits on the left of the image. This is where most people go wrong with tooth 30. 2. Find the lower back teeth on that side. Molars show two roots below the crown; premolars taper to a single root. 3. Count forward from the wisdom tooth. With a wisdom tooth present it is 32, then 31, then 30. Without one, the rearmost lower molar is usually 31.

For more detail see how to identify tooth numbers on an X-ray, and what a dental X-ray report says for the notation dentists write beside each number.

If Work Has Been Recommended on Tooth 30

This tooth attracts more crowns and root canals than almost any other, which also makes it a common source of large quotes. Before committing:

• Confirm the side. Tooth 30 is on your right. If your symptoms are on the lower left, the tooth in question is 19, not 30 — and a mismatch is worth raising.
• Ask to see the evidence on the image. A crown proposed for a lightly filled molar is a different case from one on a tooth already mostly rebuilt.
• Check the fee against your area. Root canal costs and crown costs both swing widely by location.

If the recommendation feels heavier than the problem, a second opinion dentist can read the same X-rays and put in writing whether it holds up — with no financial stake in which way you go.

Common Questions About Tooth 30

Which tooth is number 30?

Tooth 30 is your lower right first molar, the large grinding tooth partway back on the bottom right. The US Universal Numbering System numbers the 32 adult teeth 1 to 32, and the lower row is counted from left to right, which puts the high numbers on your right.

Where is tooth 30 in your mouth?

On the bottom right, about three teeth forward from the very back. The second premolar (29) sits directly in front of it and the second molar (31) directly behind. Right means your right, so on an X-ray displayed the usual way it appears on the left of the image.

Is tooth 30 a molar?

Yes, it is the lower right first molar. On an X-ray a lower molar shows two roots below the crown, while a premolar tapers to a single root.

What is tooth 30 in the FDI numbering system?

Tooth 30 in the US Universal system is tooth 46 in the FDI or ISO system used in most of the world, and lower right 6 in Palmer notation. All three refer to the same lower right first molar.

Are teeth 19 and 30 the same tooth?

No, but they are mirror images. Tooth 19 is the lower left first molar and tooth 30 is the lower right first molar. They are anatomically near-identical, which is why they are often discussed together and why mixing up the side is a common error worth checking on a treatment plan.

Last medically reviewed: September 2026