Tooth Numbers Decoded: What UL6, LR7 and 36 Mean

Your treatment plan says “Crown UL6” on one line and “RCT 36” on the next, and the dentist talked you through it in about ninety seconds. Before you paste it into ChatGPT, before you compare prices, and before you sign anything, do one simple check. Match every line on the plan to a real tooth in your mouth. A plan you can’t map tooth by tooth is a plan you can’t judge.

That’s harder than it sounds, because UK dentists use two different numbering systems, often on the same page. AI tools trained mostly on American material can also quietly swap in a third.

The two systems on UK paperwork

Palmer notation is the one with letters. Your mouth is split into four quarters, which dentists call quadrants:

• UR: upper right
• UL: upper left
• LR: lower right
• LL: lower left

Within each quadrant, teeth are numbered 1 to 8, counting outwards from the centre of your smile. So UL6 is the sixth tooth back on your upper left, and LR7 is the seventh tooth back on your lower right.

FDI notation (the international standard, ISO 3950) uses two digits. The first digit is the quadrant and the second is the tooth:

• 1 = upper right
• 2 = upper left
• 3 = lower left
• 4 = lower right

The quadrants run clockwise from your upper right as you face the world. So 36 is quadrant 3 (lower left), tooth 6. Say it as “three-six”, not “thirty-six”. Dentists do, and once you hear it that way it stops sounding like a count.

One rule catches almost everyone: left and right mean your left and right, not the left and right of someone looking at you. If you stand in front of a mirror, UL6 shows up on the right-hand side of the reflection.

The whole mouth on one grid

Here is every adult tooth in both systems, laid out as the dentist sees you when you’re in the chair:

                        UPPER JAW
   YOUR RIGHT                                 YOUR LEFT
 UR8 UR7 UR6 UR5 UR4 UR3 UR2 UR1 | UL1 UL2 UL3 UL4 UL5 UL6 UL7 UL8
  18  17  16  15  14  13  12  11 |  21  22  23  24  25  26  27  28
 --------------------------------+--------------------------------
  48  47  46  45  44  43  42  41 |  31  32  33  34  35  36  37  38
 LR8 LR7 LR6 LR5 LR4 LR3 LR2 LR1 | LL1 LL2 LL3 LL4 LL5 LL6 LL7 LL8
                        LOWER JAW

The tooth number tells you the type of tooth, and the type tells you a lot about what treatment should cost:

Root count is the reason a root canal on a 6 or 7 costs more than one on a front tooth. A private molar root canal in the UK commonly runs £500 to £1,000 at a general dentist, and more with a specialist endodontist. A front tooth is usually several hundred pounds less. If your quote charges molar prices for a tooth numbered 1, 2 or 3, ask why.

Decoding the three in the title

• UL6 = upper left first molar = 26 in FDI
• LR7 = lower right second molar = 47 in FDI
• 36 = lower left first molar = LL6 in Palmer

Notice that UL6 and 36 are both first molars, just on different jaws. Both are big back teeth that take most of the chewing load. They’re where crowns and root canals tend to land.

You might also see Palmer written with a corner symbol instead of letters, something like 6┘ or └6. The bracket shows which quadrant: the vertical line sits on the side nearest the middle of your mouth, the horizontal line above or below shows lower or upper jaw. Software output tends to convert these to UR/UL/LR/LL. Handwritten notes often don’t.

Baby teeth use letters A to E in Palmer (so a child’s plan might say “ULE”) and quadrants 5 to 8 in FDI (so 55 is a baby upper right second molar). If your plan is for an adult and you see a 5x, 6x, 7x or 8x number, either you’ve got a retained baby tooth, which happens, or there’s a typo worth querying.

The American trap your AI tool might fall into

The US uses the Universal system, which numbers teeth 1 to 32 in one continuous loop. ChatGPT, Gemini, Claude and Copilot have all read far more American dental content than British, and if you don’t tell them which system you mean, they may guess wrong on any number between 11 and 32. Every one of those numbers means something in both systems.

The clash is real. Look at “tooth 14”:

Different side, different tooth type, different price bracket. An AI explaining “root canal on 14” under the US system will tell you it’s a three-rooted molar on your left. Your dentist means a one- or two-rooted premolar on your right. Any cost comparison built on that answer is wrong from the first line.

Numbers like 36, 37, 38, 46, 47 and 48 are safer because they don’t exist in Universal, so a decent model will usually work out that you mean FDI. Don’t rely on it. State the system every time.

A worked example

Here’s a realistic private plan from a high-street practice. The patient has been told they need “a bit of work on the left side”.

TREATMENT PLAN – Private
Exam & radiographs (2 BW)                     £85.00
UL6  MOD composite                           £195.00
26   Endodontics (molar)                     £780.00
26   Porcelain bonded crown                  £695.00
LL7  O composite                             £120.00
36   Extraction                              £150.00
46   Implant + crown                       £2,650.00
                                    TOTAL  £4,675.00

Decode each line against the grid:

Three things jump out once you’ve mapped it.

First, UL6 and 26 are the same tooth, so you’re being quoted a large white filling (MOD means it covers the mesial, occlusal and distal surfaces: front side, biting surface and back side) and a root canal and a crown, all on one molar. That can be legitimate. A filling is sometimes placed first to rebuild the tooth before root canal treatment. But £195 + £780 + £695 = £1,670 on one tooth is a good question to put to the dentist: is the filling a core build-up for the crown, and is it already included in the crown fee at some practices?

The second issue is bigger. The extraction is on 36, lower left. The implant is on 46, lower right. If the plan is to replace the tooth being taken out, those numbers should match. Either there’s an existing gap on the lower right you already knew about, or someone has typed 46 for 36. A single wrong digit puts a £2,650 implant on the wrong side of your jaw, at least on paper, and on paper is what you’ll be signing.

Third, the patient was told “work on the left side”. Five of the six treatment lines are on the left. One isn’t. Before mapping, nobody would have spotted that.

Getting an AI tool to do this properly

Remove your name, date of birth, address and NHS number before you paste anything. Then give the tool the context it lacks. A prompt that works well in ChatGPT, Claude or Gemini:

I'm a patient in the UK. Below is my dental treatment plan.
UK dentists use Palmer notation (UR/UL/LR/LL + 1-8) and FDI
two-digit notation (quadrants 1-4). Do NOT use the US Universal
1-32 system.

1. Convert every line to both Palmer and FDI, and name the tooth.
2. Tell me which lines refer to the same tooth.
3. Flag any line where the tooth doesn't match the treatment
   logically (e.g. an implant on a different tooth from the
   extraction).
4. List questions I should ask the dentist.

[paste plan here]

Check the first answer against the grid above before trusting anything else it says. If it calls 26 a “lower” tooth or puts 14 on your left, it has slipped into the American system. Correct it and ask again. The conversion is mechanical, and any decent model gets it right once told. Its opinions on prices and clinical need are much less reliable, and that’s why the tooth map has to be solid before you ask for them.

NHS plans use the same numbers

An NHS FP17DC treatment plan in England lists teeth the same way, but you pay by band rather than by item. From April 2025 those were £27.40 for Band 1, £75.30 for Band 2 and £326.70 for Band 3 (check nhs.uk for the current year’s figures). The numbering still matters. A Band 3 course covering crown work on 26 shouldn’t come back with a separate private line for “26 build-up” unless the dentist has explained that you’ve chosen a private option for that tooth. Mixed NHS and private plans are allowed, but every private item has to be written down and agreed by you. Mapping each line to a tooth is how you spot which parts are which. For the band rules, the codes and what’s included in each, see Treatment Plans Explained.

Doing it in your own mouth

Open your mouth in a mirror, or better, use your phone’s front camera with the flash on. Find your two upper front teeth, and remember the mirror flips left and right. Count back from the centre on the side the plan names. The 6 is usually the first big, square tooth with several cusps on top. If you count to 6 and land on a gap, a crown you already have, or a tooth the dentist never mentioned, write it down.

Then ring the practice and read out the tooth number and the treatment, and ask them to confirm which tooth they mean. Receptionists get this question rarely enough that you may be passed to the dentist or nurse, and that’s fine. A practice that can answer “is the implant on 36 or 46?” in one sentence is one you can probably trust with the rest of the plan. If they can’t, that’s a reason to get a second quote before you pay a deposit.