Now that we've learnt the equivalent of north/east/south/west on your mouth map, our next step is to name the towns and cities! In this case that means knowing which tooth is which and being able to describe it in a way that everyone knows what you're talking about! To do this we use the modified Triadan system, in which each tooth has a standard identification number. If you know your numbers, you will always know where you are :)
For this system each tooth has a code consisting of three numbers. The first number depicts the quadrant the tooth is located in. The first quadrant is the top right, the second the top left, third bottom left and fourth bottom right. Sounds confusing? Yes! However, it's a lot easier to remember if you picture an animal looking straight at you with it's mouth open. Start at the top left from your own view and number the quadrants clockwise from there, as our lovely assistant Megan is demonstrating below!
Top tip: if your dog or cat still has it's baby teeth the quadrant numbering is different, but also easy to remember as it's just a continuation of the clockwise counting. Quadrant 1 becomes 5, 2 becomes 6, 3 becomes 7 and 4 becomes 8!
The second and third number in the code tell us which tooth is which, counting from the most mesial to the most distal tooth.
- Incisors: 01, 02, 03
- Canines: 04
- Premolars: 05, 06, 07, 08
- Molars: 09, 10, 11
This numbering is easiest to understand in dogs, as they have 42 teeth and don't skip any numbers. However, cats have a more specialized set of teeth and therefore have less teeth (only 30). On the top jaw they are 'missing' the 1st premolar and on the bottom jaw the 1st and 2nd premolar. Nevertheless the upper carnassial tooth is the fourth premolar and therefore is given the 08 code, where the lower carnassial tooth is the first molar and therefore is given th 09 code. Thus in cats we simply 'skip' the missing premolar numbers.
Top tip: baby tooth follow the same numbering rules. Baby (deciduous) dentition doesn't include molars, but there are teeth that visually look like these. This is because deciduous premolar teeth visually look like the adult tooth that will eventually grown behind it. In other words the baby tooth that looks like the adult lower carnassial (first molar in adult) is actually the fourth premolar! And the tooth that looks like the adult upper carnassial (fourth premolar in adult)? That's actually the third premolar!
These two number codes combine to make the three number code that defines each tooths location. For example: 108 is the right upper carnassial (P4), 307 is the lower left third premolar, 411 is the lower right third molar and 204 is the upper left canine tooth!
Knowing this and your directional terms from the last post you should be able to describe where anything is in any mouth you come across! This is the last of our blog posts dedicated to anatomy and terminology. That doesn't mean there isn't a lot more to learn, but this will become the focus of our 'Sunday Structure' Anatomy Quiz! Exclusive to Instagram stories, make sure you're following us @vetsmiles to learn some interesting tidbits each week!
Next up: an introduction to the oral examination!!
Skull pictures sourced from wikicommons and edited with numbering
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