Counting Teeth and Tooth Identification

Counting your teeth and identifying their surfaces involves a very precise method.

Have you ever wondered what your dentist means when they are examining and counting your teeth and they start saying a string of numbers and letters? When dentists and dental hygienists talk about numbers and letters as they peer into your mouth, they are identifying specific teeth. Using a coding system of letters and numbers allows dentists to specify which teeth have decay or other problems.

CAUTION – things are about to get complicated!

Each tooth has two numbers. For the first number we split the mouth up into 4 quadrants. Top right (quadrant 1), Top left (quadrant 2), Lower left (quadrant 3), Lower right (quadrant 4).

For the second digit in the number we use the following code:

Central incisor -No.1, Lateral incisor– No. 2, Canine – No. 3, First premolar – No. 4, Second premolar – No. 5, First molar – No. 6, Second molar – No. 7, Third molar (also known as the ‘wisdom tooth’)– No. 8. Using these two sets of numbers combined, your dentist can identify each tooth in your mouth. The first number signifies which quadrant of the mouth the tooth is located in, and the second number identifies the tooth type. So your upper right central incisor will be referred to as tooth 11 (and your dentist will say ‘one-one’, not ‘eleven’) and your lower left wisdom tooth is a 38 (‘three-eight’).


Phew…. you got that?

Baby there’s more….

With baby teeth there are 20 deciduous (baby) teeth, five in each quadrant. So a similar numbering system exists for baby teeth, except that the quadrant numbers start at 5. Top right (quadrant 5), Top left (quadrant 6), Lower left (quadrant 7), Lower right (quadrant 8). So your upper right deciduous central incisor will be referred to as tooth 51 and your lower right first premolar will be referred to as tooth 84. Sometimes both adult teeth and baby teeth will be present in the mouth at the same time. This can mean the tooth numbers from both charts are mixed together.


Now to the surfaces of the teeth:

Every tooth has 5 surfaces each with a different name. A tooth has two proximal surfaces, or surfaces that normally touch another tooth.  There is a surface that is oriented toward the midline of the dental arch and another that is oriented away from the midline of the arch. The mesial (M) is the proximal surface closest to the midline of the arch and the distal (D) is the proximal surface furthest away from the midline of the arch. The facial is the surface of a tooth that faces towards the lips or cheeks. The labial (L) is the surface of an anterior tooth that faces the lips and the buccal (B) is the surface of a back tooth that faces the cheeks. The surface of a tooth facing towards the tongue is called the lingual (L). Chewing surfaces of a front tooth is the incisal (I) and for a back tooth it’s called the occlusal (O).


Charting accurately means knowing numbers and surfaces.

So when you come in for a check up with your dentist they will have a look around and if you have any existing treatment we will put that in your chart using the letter and numbering code talked about earlier. For example if you have a composite filling which most patients call a white filling the dentist may say to their dental assistant there is an existing composite on the 34 MOD. So then we know that you have a filling on your lower left first premolar on the mesial, occlusal and distal surfaces of that tooth.

I hope this gives you an understanding of what we may be talking about when you come in for your check-up and hear us saying funny numbers.


By Kelsi Mitchell

Cert III Dental Assistant