Canadian Tooth Numbering System (By The Numbers)

Have you ever wanted to know what the dentist is talking about when he is reading out a bunch of random numbers?  This post will discuss the tooth numbering system that dentists use in Canada.  I will also discuss briefly the surfaces of teeth.

The mouth is divided into 4 sections that we call quadrants.  Quadrant 1 is the upper right, 2 is the upper left, 3 is the lower left, and 4 is the lower right.  If you were facing a person then quadrant 1 is YOUR upper left and then go clockwise and you are going 2, 3, 4.

Within each quadrant of your mouth there are 8 teeth.  Teeth 1 and 2 are the incisors.  3 is the canine (cuspid).  4 and 5 are bicuspids.  6, 7, and 8 are molars.  The 6 is your 6 year molar, the 7 your 12 year molar, and the 8 is your wisdom tooth.

Identifying a tooth is easy.  All tooth numbers are a combination of the quadrant and then the tooth number.  For example, tooth number 14 would be the upper right bicuspid.  Tooth 21 is the first incisor on the top left.  How about your bottom right wisdom tooth?  This would be tooth number 48.

There are 4 additional quadrants used in dentistry.  These are used to identify primary or baby teeth.  Quadrant 5 is the baby tooth version of quadrant 1.  Quadrant 6 is the baby tooth version of quadrant 2 and so on and so forth.  For example if you were referring to tooth 51, this is the baby first incisor.  Including wisdom teeth there are 32 adult teeth and 20 baby teeth.

In addition to tooth numbers dentists also describe a tooth or filling by its surfaces.  A tooth has the following services:

M – mesial, the front of the tooth
D – distal, the back of the tooth
O – occlusal, the top of the tooth
B – buccal, the outside surface of the tooth (facing cheek)
L – lingual, the inside surface of the tooth (facing tongue)

For example if your dentist says you need a filling 16MOD.  This means that the filling is on the top right first molar, and the mesial, occlusal, and distal surfaces are involved.



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10 replies
  1. says:

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  2. patillero
    patillero says:

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  3. Jeffery
    Jeffery says:

    Everything is very open with a very clear clarification of the issues.
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  4. Gordon Hamilton
    Gordon Hamilton says:

    I read your article (and other similar articles). They all seem to be from the perspective that the identified teeth are in your mouth. What if a certain tooth never existed. Say that permanent tooth #13 never developed but was just a space between tooth #12 and the next tooth. Further assume that the two teeth just back from the aforementioned space had been capped with a bridge-cap. Would it be obvious to a dentist what the numbers of the two capped teeth would be? Would they be #14 and #15 or would they be #13 and #14? Can a professional please reply via email as this is my current dilemma?

  5. thjomha
    thjomha says:

    Great question! So the numbering of the teeth is determined by where that tooth would be located in an ideal mouth. So yes is someone was missing tooth 12 and tooth 13 was in its spot….we still call it 13. A dentist can usually figure out which tooth it is by studying the tooth and root form. As for upper bicuspids (14 and 15) this can be a bit tricky. Many patients who have had orthodontics will be missing either 14 or 15. We usually just make an educated guess based on X-ray since 15 usually has one root and 14 usually has a bifurcated root. Sometimes I call a tooth 15 until I extract it and realize it’s 15! And as for bridge we still maintain original tooth numbers. It is obvious to the dentist what tooth numbers are involved in the bridge. This is usually confirmed by X-ray. Hope this helps. -taha

  6. Michaela
    Michaela says:

    Thank You for this post!
    I am a Medical Office Assistant graduate who just got a job at a Dental Office. It is a steep learning curve and your article is a great help.

  7. Abby Taylor
    Abby Taylor says:

    How does the primary numbering system work? I am an RDA in Austin, TX but I am moving back home to Canada and going to hygiene school so I am trying to relearn a whole new numbering system!

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