Diastemata in horses are among the most common and painful dental problems faced by owners of senior horses. Although these defects can occur in young animals as a developmental abnormality, in older horses they are usually acquired. This results directly from the particular structure of hypsodont teeth.
Why do gaps develop between senior horses' teeth?
Normally, a horse's molars and premolars fit very closely together, forming a continuous grinding surface for feed. With age, this mechanism weakens for two main reasons:
- Changes in the shape of the reserve crown: A horse's teeth are not perfect cubes. Their reserve crown , hidden in the gum, tapers towards the root. As the horse ages and the tooth continually moves outwards (erupts), its narrower part appears at the gum line. This naturally creates gaps, known as diastemata.
- Loose teeth (periodontal disease): In older horses, the reserve crown is short. The tooth loses its firm anchorage in the socket compared with an 8-10-year-old horse. Chewing forces cause the teeth to move, opening gaps where food collects.
How pain develops: a diastema as a food trap
A diastema in a horse is not painful in itself; the problem is what happens inside the gap:
- Hay or grass fibres are forced into the gap during chewing.
- The gap is often narrower at the chewing surface than at the gum, trapping food so that it cannot be removed naturally.
- The trapped feed begins to rot and ferment, causing severe gum inflammation (periodontitis).
- Bacteria destroy the periodontal ligaments, which can lead to infection of the jawbone or painful sinusitis.
Symptoms of diastemata in horses - what should you look for?
An affected horse experiences severe pain when biting down. The most common signs are:
- Quidding: Often described as 'spitting out cigars': dropping balls of chewed hay.
- Bad breath: A rotting smell noticeable when grooming your horse.
- Headshaking: A response to pain, particularly when eating or being ridden.
- Changes in feed preferences: Your horse readily eats soaked mash or grass pelletsbut avoids hay.
- Facial swelling and asymmetry: A sign of advanced inflammation.
How can you help an older horse? Treating diastemata
Dental problems in senior horses require checks every 6 months. Your vet may take the following steps:
- Mechanical cleaning of the gaps: Removing rotting material gives your horse immediate relief.
- Diastema widening: A procedure using a special burr to shape the gap so that feed can fall out naturally.
- Dental fillings: Blocking the gap with a special material to prevent food from reaching the gum.
- Changing to a liquid diet: Replacing tough hay with soaked forage (mash), which does not become wedged in the gaps.
Sources and bibliography:
- Dixon, P. M., et al. “Equine periodontal disease: A study of 400 cases”.
- N.M. Kennedy, P.M. Dixon. “Equine periodontal disease”, Equine Veterinary Education.
