When using the Triadan classification for identifying individual teeth the horses' mouth is split into 4 arcades.

Each arcade has up to 11 teeth. The horses 4 middle incisors (2 form the top row 2 from the bottom) are number 1. All other teeth are then numbered consecutively from there. Each of the 4 arcades is numbered 1 - 4. The two numbers can then be joined to specify any single tooth.

Ageing Horses

There are many reasons why the age of a horse should be considered as important. Suitability for rider, insurance policies, prognosis of disease and forecasting the working life of the horse are just a few.

All first teeth with a permanent tooth to follow are called deciduous teeth (baby teeth to us). Deciduous incisors are smaller, whiter and the occlusal tables are more oval than permanent incisors. Permanent incisors are larger and squarer, initially with the occlusal surface covered with cement and are yellowish in colour.

The 01's (central incisors) erupt within a few days of birth.

The 02's (middle incisors) erupt between 4 - 6 weeks.

The 03's (corner incisors) erupt between 6 - 9 months.

Horses are born with 06 - 08's (premolars) on both upper and lower arcades.

The 09's erupt as permanent molars at 1 year

The 10's erupt as permanent molars at 2 years

The 11's erupt as permanent molars at 3 - 3.5 years

The most suitable teeth for ageing horses are the lower incisors. The eruption of the cheek teeth can be used to assist until all have erupted but after this the situation of these teeth make them unsuitable for assisting when ageing horses.

Changes in the occlusal surface

It is important to describe what we can see when ageing horses before we determine what we see at different ages.


Yellow brown in colour. Situated on the labial edge (towards the horses lips) of the occlusal surface.Consists of dentine that wears down into the pulp chamber. Initially seen as a linear stripe (parallel to labial edge) but as the horse ages the dental star becomes round and eventually central on the occlusal surface of the tooth.

CUP (infundibulum)

Enamel folding throughout part of the incisor showing on the occlusal surface. Superficial half is empty and fills with food particles making its appearance black. The bottom of the cup is filled with cement. Once the cement part of the cup is in occlusion the cup is filled or has disappeared. The cement core and surrounding enamel ring is called the mark.


In younger horses the mark is oval. As the tooth wears the mark becomes smaller and rounder and moves lingually (towards the horses tongue). Eventually the cement of the infundibulum bottom wears away and the mark disappears.

Angle of incisors

When viewed from a side profile young horses incisors are positioned in a straight line with each other. As the horse gets older, the angle that the upper and lower incisors make becomes more acute.

It is through noticing change in the appearance of the occlusal surface of the incisors that we can age a horse.