Tooth Numbering Chart: FDI, Universal and UK Notation
Tooth numbering gives every tooth a code, so a treatment plan or X-ray report cannot be misread. Outside the USA most records use the FDI two-digit system[3][5]: the first digit is the quarter of the mouth (1 upper right, 2 upper left, 3 lower left, 4 lower right) and the second is the tooth, counted from the front tooth (1) back to the wisdom tooth (8)[5]. So 36 is the lower left first molar. US dentists number teeth 1 to 32[4]; UK letters often use codes such as UR6[6].
How many teeth adults and children have
People usually have 20 baby (primary) teeth, which start to come through at about 6 months of age and fall out at different times during childhood. By the age of 21 all 32 permanent teeth have usually come through[1]. Some adults have fewer than 32 because wisdom teeth never formed, never came through or were removed; our guide to wisdom teeth explains when they are left alone and when they are taken out.
Each half of each jaw holds the same sequence of 8 permanent teeth, from the middle of the smile backwards. Tooth numbering follows this sequence, which is why the last digit of an FDI number tells you the type of tooth[5]:
| FDI tooth digit | Tooth | Per quarter | Main job |
|---|---|---|---|
| 1 and 2 | Central and lateral incisors | 2 | Cutting food; most visible when you smile |
| 3 | Canine (eye tooth) | 1 | Tearing food; guides the jaw when you move it sideways |
| 4 and 5 | First and second premolars | 2 | Crushing and chewing |
| 6, 7 and 8 | First, second and third molars (8 = wisdom tooth) | 3 | Grinding food |
The digit-to-tooth sequence is from Su et al. (2025)[5]; the jobs are a general description, not a clinical classification.
The parts of a tooth
A tooth is made of four tissues. Three of them, enamel, dentin and cementum, are hard tissues; the fourth, the pulp in the centre, is soft and contains nerves, blood vessels and connective tissue[2]. The table shows what each part is and why it appears on treatment plans.
| Part | What it is | Why it matters on a plan or report |
|---|---|---|
| Enamel | The hard, calcified outer layer of the crown. It contains no living cells, so it cannot repair damage from decay or wear[2] | Lost enamel does not grow back; see tooth wear and enamel erosion |
| Dentin | The layer beneath enamel and cementum, with microscopic tubules that let heat, cold or acid stimulate the nerves when the enamel is lost[2] | Exposed dentin is a common reason for sensitive teeth |
| Pulp and root canal | The soft centre of the tooth with nerves and blood vessels; the root canal is the part of the pulp space inside the root[2] | Treated when inflamed or infected; see root canal treatment |
| Cementum | Hard connective tissue covering the root, which anchors the periodontal ligament[2] | Covers roots exposed by receding gums |
| Crown, neck and root | The crown is the visible part, normally covered by enamel; the neck is where the crown joins the root[2] | A dental crown restoration covers the clinical crown |
| Gums, bone and periodontal ligament | Gums cover and protect the roots; the alveolar bone surrounds the roots; the periodontal ligament connects the root to its socket[2] | Measured in a gum check; see gum disease |
The FDI two-digit system
The two-digit system was described by Jochen Viohl in Berlin in 1966 and proposed by the Fédération Dentaire Internationale (FDI) for worldwide use in 1970[4][8]. Each tooth gets two digits: the first is the quadrant and the second is the tooth within that quadrant[4][5]. The quadrants run clockwise as you face the patient, starting from the upper right (1), then upper left (2), lower left (3) and lower right (4); the second digit counts from the central incisor backwards[5].
- 11 and 21 are the two upper front teeth (right and left);
- 16 and 26 are the upper first molars;
- 36 and 46 are the lower first molars;
- 18, 28, 38 and 48 are the four wisdom teeth.
The system is widely used in clinics and universities across Europe and Asia[5]. A 1993 review described it as used throughout the world, but not in the USA[3], and by 1989 it had been adopted by the International Organization for Standardization (ISO/TC 106), the World Health Organization and Interpol, among others[4]. Read each number as two separate digits: “two-one”, not “twenty-one”. “Right” and “left” always mean the patient’s right and left.
Baby teeth have separate codes in each system. If your child’s treatment plan shows codes you do not recognise, ask the dentist to point to the tooth.
The US Universal system and UK notation
The Universal system numbers the permanent teeth from 1 to 32. It begins with the upper right third molar (1), counts around the upper jaw and down to the lower left third molar (17), and finishes with the lower right third molar (32)[4]. It is the system US patients usually see[3].
The older Zsigmondy/Palmer system numbers the teeth 1 to 8 from the central incisor to the third molar in each quadrant and marks the quadrant with a grid symbol around the number[4]. In UK and Irish dental hospitals surveyed in 2016, the notation systems in use were, in order of frequency, the Alphanumeric, the Palmer and the FDI system; none used the Universal system, and most referral letters from dentists used Alphanumeric notation[6]. In Alphanumeric notation the quadrant is written as letters, so UR6 is the upper right first molar and LL1 the lower left central incisor.
The same number can mean different teeth. “Tooth 12” is the upper right lateral incisor in the FDI system but the upper left first premolar in the Universal system. In one survey of 66 dental students, interns, dentists and technicians, only 56% correctly recognised which system a questionnaire was written in[7]. Before you agree to any treatment, check which system your plan uses and which tooth each number means.
Tooth numbering chart: FDI, Universal and UK
The two tables convert every permanent tooth between the three systems. Upper teeth are listed from the patient’s right wisdom tooth to the left wisdom tooth, and lower teeth from left to right, which follows the Universal count[4].
| Tooth | FDI | Universal (US) | UK |
|---|---|---|---|
| Upper right third molar (wisdom tooth) | 18 | 1 | UR8 |
| Upper right second molar | 17 | 2 | UR7 |
| Upper right first molar | 16 | 3 | UR6 |
| Upper right second premolar | 15 | 4 | UR5 |
| Upper right first premolar | 14 | 5 | UR4 |
| Upper right canine | 13 | 6 | UR3 |
| Upper right lateral incisor | 12 | 7 | UR2 |
| Upper right central incisor | 11 | 8 | UR1 |
| Upper left central incisor | 21 | 9 | UL1 |
| Upper left lateral incisor | 22 | 10 | UL2 |
| Upper left canine | 23 | 11 | UL3 |
| Upper left first premolar | 24 | 12 | UL4 |
| Upper left second premolar | 25 | 13 | UL5 |
| Upper left first molar | 26 | 14 | UL6 |
| Upper left second molar | 27 | 15 | UL7 |
| Upper left third molar (wisdom tooth) | 28 | 16 | UL8 |
| Tooth | FDI | Universal (US) | UK |
|---|---|---|---|
| Lower left central incisor | 31 | 24 | LL1 |
| Lower left lateral incisor | 32 | 23 | LL2 |
| Lower left canine | 33 | 22 | LL3 |
| Lower left first premolar | 34 | 21 | LL4 |
| Lower left second premolar | 35 | 20 | LL5 |
| Lower left first molar | 36 | 19 | LL6 |
| Lower left second molar | 37 | 18 | LL7 |
| Lower left third molar (wisdom tooth) | 38 | 17 | LL8 |
| Lower right third molar (wisdom tooth) | 48 | 32 | LR8 |
| Lower right second molar | 47 | 31 | LR7 |
| Lower right first molar | 46 | 30 | LR6 |
| Lower right second premolar | 45 | 29 | LR5 |
| Lower right first premolar | 44 | 28 | LR4 |
| Lower right canine | 43 | 27 | LR3 |
| Lower right lateral incisor | 42 | 26 | LR2 |
| Lower right central incisor | 41 | 25 | LR1 |
FDI quadrant order and tooth sequence: Su et al. 2025[5]; Universal start and end points: Al-Johany 2016[4]. UK Alphanumeric codes use the same 1–8 sequence as the Palmer system[4][6].
How to read your treatment plan
In Türkiye, private dental facilities must record each patient’s diagnosis, treatment and any X-ray records in detail together with the tooth numbers[9]. A clear plan therefore lists, for each tooth, the tooth number, the treatment, the material and the price. The lines below are an illustration of that format with our current prices, not a real patient’s plan:
| Tooth (FDI) | Treatment | Material or system | Price |
|---|---|---|---|
| 11, 21 | Laminate veneer | E.max (Ivoclar IPS e.max) | €250 per tooth |
| 36 | Root canal treatment, 3 roots | — | €180 |
| 36 | Crown | Zirconia (Amann Girrbach) | €185 |
| 46 | Implant with standard abutment | Nucleoss | €300 |
| 46 | Crown on the implant | Zirconia (Amann Girrbach) | €185 |
Consultation and the panoramic X-ray taken at the examination have no separate fee. Prices are indicative; your final written quote follows the examination and X-rays and is valid for 30 days. Unless the treatment plan changes, the written price does not change.
Some abbreviations you may meet on plans and reports from different clinics and countries:
- Surfaces: M (mesial, towards the midline), D (distal, away from the midline), O (occlusal, the biting surface of back teeth), I (incisal, the biting edge of front teeth), B or F (buccal or facial, towards the cheek or lips), L or P (lingual or palatal, towards the tongue or palate). “36 MO” is a filling on the mesial and biting surfaces of the lower left first molar.
- Treatments: RCT (root canal treatment), Ext (extraction), Imp (implant), Zr (zirconia), PFM (porcelain fused to metal, a crown type you may see on older records).
If a line is unclear, ask before treatment starts which system is used and which tooth is meant, and look at the tooth in a mirror with the dentist. You are also entitled to copies of your records; our treatment record handover checklist lists what to ask for so that your dentist at home can read them. All our prices are on the dental treatment prices page.
How to read your X-ray report
A panoramic X-ray shows all the teeth and both jaws in one image; small intraoral X-rays show one or a few teeth in more detail. Reports refer to the teeth by number, for example “periapical lesion at 46” or “impacted 38”. Words you may see:
- Radiolucent (dark on the image): an area with less mineral, such as decay, a cavity or bone loss;
- Radiopaque (bright): dense material such as enamel, fillings, crowns, root canal fillings or implants;
- Periapical lesion: a dark area at the tip of a root, often linked to an inflamed or infected pulp;
- Bone level or bone loss: how much bone supports the teeth, used to judge gum disease;
- Impacted: a tooth, often a wisdom tooth, that has not come through fully.
An X-ray report describes what the image shows; a diagnosis also needs an examination. If you are not sure which side of an image is your right side, ask the dentist who took it to point it out. How the different X-ray types compare, and how much radiation they involve, is explained in dental X-rays and CBCT.
At Ulubey Dental Clinic, Dr. Ali Cem Ulubey and Dr. Surur Ulubey take a panoramic X-ray for every patient and take intraoral X-rays in the clinic when a tooth needs a closer look; when a case needs a 3D cone-beam (CBCT) scan, Dr. Ali Cem Ulubey reviews it himself. The dentists go through the plan tooth by tooth with you, in English, Turkish, Persian (Farsi) or Azerbaijani Turkish. Words used across these guides are explained in our dental glossary.
Frequently asked questions
Which tooth is number 14?
It depends on the system. In the FDI two-digit system, 14 is the upper right first premolar: quadrant 1 is the upper right, and tooth 4 is the first premolar. In the US Universal system, 14 is the upper left first molar, which is 26 in the FDI system. Always check which system your plan or report uses before treatment starts.
What is tooth 36?
In the FDI system, 36 is the lower left first molar: the first digit 3 means the lower left quadrant and the second digit 6 means the first molar. In the US Universal system the same tooth is number 19, and in UK Alphanumeric notation it is LL6. There is no tooth 36 in the Universal system, which only goes up to 32.
How many teeth should an adult have?
Most adults have 32 permanent teeth, which have usually all come through by the age of 21. Many adults have fewer because wisdom teeth never formed, stayed in the jaw or were removed. Children have 20 baby teeth, which start to come through at about 6 months of age and fall out at different times during childhood.
Which numbers are the wisdom teeth?
In the FDI system the wisdom teeth are 18, 28, 38 and 48, because 8 is the last tooth in each quadrant. In the US Universal system they are 1, 16, 17 and 32. In UK Alphanumeric notation they are UR8, UL8, LL8 and LR8. A report that mentions an impacted 38, for example, refers to the lower left wisdom tooth.
Why does my UK dentist write UR6 instead of 16?
Many UK dentists use Alphanumeric notation, in which the quadrant is written as letters (UR, UL, LL, LR) and the tooth as a number from 1 to 8 counted from the front. UR6 is the upper right first molar, which is 16 in the FDI system and 3 in the US Universal system. A 2016 survey found Alphanumeric notation was the most used in UK and Irish dental hospitals.
Can I get my dental records with the tooth numbers?
Yes. In Türkiye, private dental facilities must record diagnosis, treatment and X-ray records in detail with the tooth numbers, and you can ask for copies of your records. Ask for the plan, the X-rays as files and a list of the teeth treated, so that your dentist at home can continue your care without guessing.
Sources
- American Dental Association, MouthHealthy. Eruption charts (accessed 26 October 2026). www.mouthhealthy.org/all-topics-a-z/eruption-charts
- American Dental Association, MouthHealthy. Tooth: the anatomy of a tooth (accessed 26 October 2026). www.mouthhealthy.org/all-topics-a-z/tooth
- Peck S, Peck L. A time for change of tooth numbering systems. J Dent Educ. 1993;57(8):643-647. PMID 8349894. pubmed.ncbi.nlm.nih.gov/8349894
- Al-Johany SS. Tooth numbering system in Saudi Arabia: survey. Saudi Dent J. 2016;28(4):183-188. PMID 27872549 (full text PMC5110463). pubmed.ncbi.nlm.nih.gov/27872549
- Su YS, Cha IE, Mao YC, et al. Hybrid Faster R-CNN for tooth numbering in periapical radiographs based on Fédération Dentaire Internationale system. Diagnostics (Basel). 2025;15(22):2900. PMID 41300924 (full text PMC12651699). pubmed.ncbi.nlm.nih.gov/41300924
- Pemberton MN, Ashley M. The use and understanding of dental notation systems in UK and Irish dental hospitals. Br Dent J. 2017;223(6):429-434. PMID 28883553. pubmed.ncbi.nlm.nih.gov/28883553
- Shehabeldin RR, Hamama HH. Introduction of “qpdb” teeth numbering system. Heliyon. 2024;10(2):e24367. PMID 38298675 (full text PMC10827761). pubmed.ncbi.nlm.nih.gov/38298675
- Türp JC, Alt KW. Designating teeth: the advantages of the FDI’s two-digit system. Quintessence Int. 1995;26(7):501-504. PMID 8935036. pubmed.ncbi.nlm.nih.gov/8935036
- Republic of Türkiye. Ağız ve Diş Sağlığı Hizmeti Sunulan Özel Sağlık Kuruluşları Hakkında Yönetmelik (Regulation on private oral and dental health facilities), Official Gazette 6 October 2022 No. 31975, Article 22(2) (accessed 26 October 2026). www.resmigazete.gov.tr/eskiler/2022/10/20221006-1.htm
This article is general patient information and does not replace a clinical examination or X-rays.
Editor contact: [email protected] · ulubeydental.com/contact-us
