Dental ageing

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Ageing a horse based on their teeth involves assessing the presence of incisors (front teeth) as deciduous or permanent, incisor occlusal (grinding) surface, bite alignment and the presence of hooks and grooves on the upper incisors. It's important to understand the underlying tooth structure and growth to appreciate the changes we see during examination. 

As a guide, we use the following to assess foals and yearlings:

• 6 days – central incisors present
• 6 weeks – centrals and intermediates
• 6 months – all deciduous incisors present
• 1yo – 1st molar present
• 2yo – 2nd molar present.

General rules for adult incisor eruption:

• 2.5yo – permanent central incisors
• 3.5yo – intermediate incisors 
• 4.5yo – corner incisors erupted.
• 5yo – all adult incisors should be in ‘wear’  
• 6yo – corner incisors in contact labially (lip aspect)
• 7yo – corner incisors in full contact lingually (tongue aspect)

A relatively precise age can be estimated up until 6-7 years. After the age of 7 age estimations become less accurate due to numerous factors including quality of feed, environment, heredity, and disease. Dental ageing is not an exact science, but a tool used to guide our estimations. 

Younger teeth are 'softer' and have a faster eruption rate. As teeth become older the rate of eruption slows and teeth harden, which is why younger horses require a dental more often. 

Quick note: younger incisors are wider than they are tall, and older teeth are long and thin, hence the term 'long in the teeth'.