Canadian Tooth Numbering System

Dr. Taha Jomha, BMed Sci, DDS

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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