Int./Adv Teeth

Don't look a gift horse in the mouth. But why? Well because you're likely evaluating it's age -- the ancient world's equivalent of checking the price tag of a gift you've received :)

But what would you be checking for? Well you know (since you either already know OR you read the beginner section :) that a horse's teeth never stop growing. So it stands to reason that they change shape over the years and with practice you can learn to judge the horse's age. Now this is unfortunately never really accurate beyond about age 7 -- but it can, at least, put you in the right ballpark. Why not accurate? Because as we know, wear changes based (among other things) on diet. So every horse's teeth will change at a slightly different rate.

So the very first thing to check -- does your horse still have baby teeth (if so, they're under the age of five). If they do, how many do they have?

Incisors

• Deciduous central incisors - come in at birth or within the first two weeks
  
• Deciduous middle incisors - come in at 4-6 weeks old
  
• Deciduous corner incisors - come in at 6-9 months
  
• Permanent central incisors - come in 2.5-3 years
  
• Permanent middle incisors - come in 3.5-4 years
  
• Permanent corner incisors - come in 4.5-5 years

Note, while it's a lot harder to check the molars, they also come in on schedule:

Premolars (the set at the front of the mouth, meets the bars)

• Wolf teeth (technically PM1) - no deciduous set, permanent ones at 5-6 months (if ever)
  
• All three other deciduous sets: come in at birth or within the first two weeks
  
• Permanent PM2 - 2.5 years
  
• Permanent PM3 - 3 years
  
• Permanent PM4 - 4 years

Molars (the set at the back of the mouth)

• There are no deciduous molars. The horse gets permanent ones as they get older.
  
• 1st - 9-12 months
  
• 2nd - 2 years
  
• 3rd - 3.5 years

Note for both molars and premolars the count goes from front to back. PM1, the wolf teeth, are closest to the incisors, PM2 the next tooth back, etc.

Your horse is said to have a "full mouth" about age 5 when all permanent incisors, premolars and molars are in. How to tell? Deciduous teeth tend to be smaller (I know, big surprise eh?), whiter, and have several grooves on the surface. If the teeth are big, yellow, and rectangular in shape, they're probably permanent. A good thing to do is find a horse who you know is 3 or 4 years of age and look at their teeth to see the difference between the baby teeth and the adult teeth. Ummmm find either a very patient horse or get somebody to help you do this the first time ;) Just a suggestion.

Note that if the gelding or stallion has canines it means they must be at least 4 years old (often these don't come in till 5).

After 5 things get a little trickier, but there are things you can specifically look for:

• The cups - in young horses you can see a cup in the incisors (essentially an oval shaped concave area that will eventually be worn away). By 9 the cups are gone (usually leave central incisors about 7, middle around 8, and corner around 9).
  
• The dental star - this appears at about 6 years of age (in the central incisor - other incisors to follow in the next year or two). If you look at the top of the incisor, you'll see a dark yellow/brown circular/star shape (technically what you're seeing is a dentin-filled pulp chamber -- don't you feel smarter now?). At this age it starts out as a narrow line and morphs into a rounder and bigger shape with age - most dramatic around age 10 (and then usually disappears entirely between 15 and 20). It's toward the front of the tooth.
  
• The hook - at about 7 years of age (and sometimes again at 9) a hook will appear on the upper corner incisor.
  
• Galvayne's Groove - a dark line that runs longitudinally on the upper corner incisor. This shows up about 10 years old, is half way down the tooth at 15, all the way down the tooth by 20, gone by 25. Useful if it's there but not all horses show this.

Then the other thing to evaluate (requires more practice) is the shape of the teeth:

• On a young horse the shape will be oval, then it will square off to become more rectangular. In old age the corners are worn and you end up with an almost triangular shape.
  
• Similarly the angle (when viewed from the side) at which the incisors meet changes. A young horse the teeth meet almost straight up and down like | (technically about 135deg for those who like those things - it's hard to show that accuracy in ascii art :). In an older horse though (age 20+), the angle has changed dramatically so that the incisors meet at almost 90deg (looks like < then).