Aging a Horse by Teeth Photographs

Since 1900, experts have used the shape of horses’ teeth to estimate their ages. But recent research has demonstrated that Galvayne’s system for assigning specific dental features to specific ages is inaccurate.

Examining the biting surface of an incisor’s incisors for dark marks (cups), light brown lines (marks) and spots (stars) may offer clues as to a horse’s age.

Galvayne’s Groove

Use of horse teeth as an indicator of age has long been utilized within the industry; however, as horses age their dental features become less reliable – the so-called “seven-year hook” and Galvayne’s groove in their incisor teeth being two such indicators.

Galvayne’s Groove is a dark or brownish line on the lateral surface of an upper corner incisor that typically begins appearing around age 10 and extends halfway down by 15; by age 20, this groove was present across its entirety; at 25 it started dissipating, eventually disappearing altogether by age 30.

Horsemen have long looked to Galvayne’s Groove as an indicator of an equine’s age. However, it must be remembered that teeth reflect many factors including environmental conditions, diet and vices such as crib biting. Even so, reasonable accuracy can still be obtained up to approximately age 10. After this point it should only be used as a guide.

Seven-Year Hook

Changes to a horse’s teeth occur throughout its lifetime, providing us with a way of estimating its age. For best results, examine changes on incisors located at the front of its mouth as these can easily be accessible for examination. Watch its biting edge for wear indications that could indicate its age such as brown lines (cup), light brown marks (dental star), or an undulated surface with chewing surface irregularities that suggest wear from chewing activity.

At approximately three and a half years, deciduous central incisors become pushed out of their proper places by permanent ones that come in below them and start grinding against each other, eventually appearing more oval-shaped due to this wear and tear.

The seven-Year Hook, also referred to as an indicator of age in horses, typically dissipates by 20 years old.


Cups are deep indentations on the chewing surfaces of a horse’s incisors caused by different hardnesses among their teeth (enamel, dentin and cementum) wearing away over time and wear marks appearing. As these indentations become more prominent with time they form what’s known as a cup-like structure which is encircled by an enamel ring above its biting surface.

As horses age, their cups diminish to become something known as a “dental star.” Dental stars first begin appearing around age 8-10 as the cup wears away and becomes worn away; these dark spots consisting of pulp cavities filled with secondary dentin change shape from oval, triangular and eventually round over time as their shape shifts with growth.

Aging horses by their teeth is an accurate method for estimating their approximate age up to approximately five years old, but beyond this point accurate determinations become more challenging due to factors like diet and vices which can have a substantial effect on a horse’s teeth, making it appear younger or older than it actually should be.


Before age 5, horses’ teeth usually erupt at predictable intervals. After this point, aging a horse becomes more complicated but still possible by looking at various tooth-related features – marks, cups, or stars on incisors for example – that indicate their age.

First to note is the shape of an incisor profile; over time it progressively becomes slanted from upright in young horses to almost horizontal at their corners in old horses. Next comes brown lines (marks) and spots (cups), followed by yellowish-colored dental stars appearing at their centers; these replace pulp cavities with secondary dentin to form irregular rectangles or ovals and eventually round shapes at corners, moving towards center occlusal surfaces as age advances.

These characteristics may provide clues as to a horse’s approximate age; however, these methods aren’t reliable and other factors like diet and dental care may influence how quickly a horse ages.

Angle of Teeth

As horses age, the angle of their incisors changes as well. Young horses typically have almost vertical incisors; as they mature they shift more horizontally before becoming squarer again as maturity nears. When aged horses reach old age their incisors narrow more than they widen, giving rise to the old saying “long in the tooth”.

As well as paying attention to the “hook” and groove, you should also focus on observing a “star.” A star is a small brown mark found on an upper corner incisor’s biting surface caused by stain accumulation on a tooth’s pulp due to wear-and-tear over time. Stars serve as useful indicators of age in horses since they reveal whether its teeth have worn down to gum level as permanent premolars have taken the place of deciduous ones and whether any permanent molars have started full eruption.






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