The tooth numbering system used in Australia is FDI two-digit notation, where the first digit is the quadrant of your mouth and the second is the tooth position counting out from the midline. Under that system your upper right first molar is tooth 16, said out loud as one six rather than sixteen. Patients often ask me why a treatment plan lists numbers instead of names, so here is the plain English version of dental tooth numbers.
Key takeaways
- FDI two-digit notation is the international standard and the one you will usually see on Australian charts, quotes and referrals.
- Quadrants 1 to 4 cover adult teeth, starting at the upper right. Quadrants 5 to 8 cover the same four areas for baby teeth.
- The second digit counts outwards from 1 at the midline to 8 at the wisdom tooth.
- The Universal system runs 1 to 32 and is mainly American. Palmer notation uses a bracket symbol and still appears in orthodontics and older paper records.
- Left and right are described from your point of view, not the viewer's, which is why the sides look reversed on an X-ray.
- Tooth numbers and Australian dental item numbers are two completely different things.
Why dentists number teeth at all
Names on their own are not precise enough. An adult mouth has four first molars, and calling one of them the big tooth up the back does not tell a laboratory technician, a health fund or a colleague which one you mean. A number does the job in two characters with no room for confusion.
A shared shorthand
Numbering also travels well. A chart written in Melrose Park can be read by a specialist across the city or a dentist overseas without translation, which matters if you move, need urgent care away from home, or want a second opinion. Australian dental schools and the profession more broadly teach the same notation used through most of Europe, Asia and South America.
Where you will see the numbers
Tooth numbers appear on treatment plans and written quotes, on referral letters, in radiograph reports, in orthodontic records and in the notes read back to you at a check-up. If you have ever heard a dentist call out a run of numbers and letters while an assistant types, that is charting. The tooth number comes first, then the surfaces involved and what was found.
FDI two-digit notation, step by step
The FDI World Dental Federation system, published internationally as ISO 3950, gives every tooth a two-digit label. The two digits are read separately, which is why you hear four seven rather than forty seven.
The first digit is the quadrant
Your mouth divides into four quadrants: a vertical line between the two front teeth, and a horizontal line between the upper and lower jaws. For adult teeth, 1 is upper right, 2 is upper left, 3 is lower left and 4 is lower right. The count always starts at the upper right and works around the mouth in order.
The second digit is the position
Counting outwards from the midline, the central incisor is 1, the lateral incisor is 2, the canine is 3, the first premolar is 4, the second premolar is 5, the first molar is 6, the second molar is 7 and the third molar or wisdom tooth is 8. Put the digits together and tooth 23 is the upper left canine, tooth 47 is the lower right second molar, and tooth 38 is the lower left wisdom tooth.
Baby teeth use quadrants 5 to 8
Children's teeth follow the same logic with different quadrant digits: 5 is upper right, 6 is upper left, 7 is lower left and 8 is lower right. Position digits only run 1 to 5, because each quadrant of a child's mouth holds two incisors, a canine and two molars, with no premolars and no wisdom teeth. So tooth 54 is the upper right first baby molar. If you want to know when each of those teeth is likely to appear, our guide to baby teeth eruption order sets out the usual sequence.
The plain English name for every tooth
The front teeth
The four teeth at the front of each jaw are incisors. The two in the middle are central incisors and the ones either side are lateral incisors. They are shaped like small chisels and are built for cutting. Next along sits the canine, sometimes called the eye tooth, with a single point and the longest root in the mouth.
The back teeth
Behind each canine sit two premolars, first then second, usually with two cusps each. Then come the molars, broad teeth with several cusps that do most of the grinding. First molars typically arrive around age six, second molars around age twelve, and third molars in the late teens or twenties if they arrive at all. Wisdom teeth are the ones most often left out of a count, and when they cause trouble they can do it quietly, as covered in our article on wisdom tooth cysts.
How many teeth should there be
An adult typically has 32 teeth including four wisdom teeth, or 28 without them. Children have 20 baby teeth. Some people are born without one or more adult teeth, most commonly a lateral incisor, a second premolar or a wisdom tooth, and on a chart that simply shows up as a number that is not there. If a baby tooth is lost well before its adult replacement is ready, the spacing can drift, which is why early loss of baby teeth is worth reviewing rather than ignoring.
The other systems you may come across
Universal numbering
The Universal Numbering System is used mainly in the United States. It runs a single count from 1 to 32, starting at the upper right wisdom tooth, travelling along the upper arch to the upper left wisdom tooth, then dropping to the lower left wisdom tooth and finishing at the lower right. Baby teeth take letters A to T along the same path. Under this system the upper right first molar is number 3. If you have had dental work done in America, expect to see it on those records.
Palmer notation
Palmer notation keeps the numbers 1 to 8 but marks the quadrant with a right-angled bracket drawn around the number, opening towards the side of the mouth involved. Baby teeth use letters A to E. It is compact and quick to draw by hand, and it still turns up in orthodontic records, oral surgery notes and older files. Its weakness is that the bracket does not type easily, so digital records have largely moved to FDI.
| System | Upper right first molar is written as | Numbering pattern | Mainly used for |
|---|---|---|---|
| FDI two-digit (ISO 3950) | 16, said one six | Quadrant digit 1 to 4 for adult teeth and 5 to 8 for baby teeth, then position 1 to 8 from the midline | Standard notation in Australia and most of the world, and in digital dental records |
| Universal | 3 | Adult teeth 1 to 32 starting at the upper right wisdom tooth, letters A to T for baby teeth | Clinical records and insurance claims in the United States |
| Palmer | 6 inside a quadrant bracket | Number 1 to 8 within a bracket showing the quadrant, letters A to E for baby teeth | Orthodontics, oral surgery notes and older handwritten records |
Why your right side looks like the left
Dental charts and X-ray images are labelled from the patient's perspective, as if you were looking outwards from behind your own teeth. Your upper right quadrant therefore appears on the left of the image. It is the same convention used across medical imaging, and it is worth knowing, because it explains why a screen showing a problem tooth on what looks like the left is actually describing something on your right.
A quick way to orient yourself
Find the midline first, then count outwards. Do not count inwards from the very back tooth, because a missing or unerupted wisdom tooth will throw the whole count off by one.
Reading your own treatment plan
What a line item usually contains
A typical line lists an item number, a short description, a tooth number and a fee. An item for a two-surface filling on tooth 36 means a filling involving two surfaces of the lower left first molar. Knowing the tooth number lets you check the plan matches what was discussed, and lets you ask sensible questions if it does not.
Item numbers are not tooth numbers
This one trips up a lot of people. Australian dental item numbers, set out in the Australian Schedule of Dental Services and Glossary maintained by the Australian Dental Association, describe the procedure rather than the tooth. Item 011, for example, is a comprehensive oral examination and applies to the whole mouth. Tooth numbers sit in a separate column. Health funds pay against item numbers, so a statement can list several items against one tooth, or one item with no tooth number at all.
Questions worth asking
If a number on your plan does not look familiar, ask which tooth it is and ask to see it on the screen. Any dentist should be glad to point it out. It is also fair to ask what may happen if treatment is delayed, and whether a more conservative option exists. If a tooth is coming out, understanding the stages of healing after an extraction makes the plan easier to weigh up.
Frequently asked questions
Why do dentists say one six instead of sixteen?
Because the two digits carry separate meanings. The first is the quadrant and the second is the position, so reading them as a single number would blur two pieces of information into one.
Which tooth numbering system is used in Australia?
FDI two-digit notation is the usual system in Australian practice and dental software. Palmer notation still appears in some orthodontic and surgical records, and the Universal system may show up on records from the United States.
What number is a wisdom tooth?
The position digit for every wisdom tooth is 8. So the four wisdom teeth are 18, 28, 38 and 48, working from the upper right around to the lower right.
How are baby teeth numbered?
Baby teeth use quadrant digits 5 to 8 and position digits 1 to 5. The lower left second baby molar, for example, is tooth 75.
Why is my right side shown on the left of the X-ray?
Images and charts are oriented from your perspective, not the viewer's. Once you know that, the layout stops being confusing.
Do I actually need to know my tooth numbers?
You do not need to memorise them, but recognising the pattern makes quotes, health fund statements and referral letters far easier to check, and it makes conversations about your own care more straightforward.
Book a check-up with the team at Lumi Dental
If you would like your own chart explained tooth by tooth, the team at Lumi Dental in Melrose Park is happy to take you through it on screen at your appointment, along with anything on your quote you are unsure about. You can see what a general dental check-up involves, and have a look at the current new-patient offers on our current deals page. The practice is open Monday to Saturday, with Sunday by appointment.
This article is general information only and is not a substitute for personal dental advice. Your own teeth, medical history and X-rays need to be assessed by a dentist before any recommendation can be made.
