When it comes to teeth, we have more in common with dogs and cats than we do with our horses. As brachydonts, our teeth have short crowns – the part that protrudes from the gum. But horses are hyspodonts, meaning that their teeth feature tall, enamel-covered crowns that extend well below the gum surface and continue to grow, or “erupt”, throughout life.
Until now, much of our knowledge about the structures surrounding horses’ teeth has been based on studies in brachydont species. A European research team has revealed that while equine gingiva (gums) do indeed share similarities with brachydont gingiva, they also have characteristics of their own.
“The study examined the heads of 20 equine cadavers, looking in detail at the gingival anatomy of both the incisors and cheek teeth,” says Neil Townsend MRCVS, adding that the horses had been euthanised for reasons other than dental problems. “Specifically, the researchers noted diastema – gaps between the teeth – and periodontal pockets, where gum recession extends into the periodontal ligament that anchors the tooth in its socket.
“They also looked at the natural pocket around each tooth, known as the gingival sulcus,” Neil adds. “Previously, this was thought to measure up to 5mm in depth in the horse. Every sulcus studied measured less than 3mm, however, and in 90% of teeth no more than 1mm.
“As with humans, equine gums are wrapped tightly around the teeth – so any gap that is present may indicate disease.”
Bacterial barrier
As well as outlining the first scientific description of healthy equine gingiva, the researchers gained valuable insight into periodontal disease – known as periodontitis.
“Every head examined had at least one periodontal pocket,” explains Neil. “Given that the horses used ranged from nine months to 26 years old, this shows that periodontitis affects all ages.
“All periodontal pockets present were between the teeth, which is consistent with previous anatomical and clinical studies,” adds Neil. “In humans and small animals, periodontitis can occur anywhere along a tooth and is initiated by the formation of bacteria and plaque, but horses differ in that the condition is initiated by diastema and food impaction between teeth. This destroys the gingiva and allows penetration of bacteria, leading to destruction of the tooth substance and pocket formation.”
The research also observed that the prevalence of diastema increased with age and was more common in cheek teeth than incisors. Neil concludes that such detailed anatomical knowledge helps to underpin our approach to equine periodontitis, enabling treatments used in other species to be adapted where appropriate.
“The equine gingiva is securely attached to both incisors and cheek teeth, acting as a barrier to food and bacteria,” he says. “Periodontitis begins with the breakdown of this barrier. The most effective preventative measure is regular – at least yearly – examination of your horse’s mouth by a vet, or an equine dental technician qualified with the British Association of Equine Dental Technicians (BAEDT) or the Worldwide Association of Equine Dentistry (WWAED).”
Detecting gum disease
Gingivitis (gum inflammation) or periodontitis of the incisors is easiest to spot, given the location of these biting teeth at the front of the mouth. Food packed between the incisors may be visible, and once removed will usually reveal that the gum has receded to expose more of the tooth. If left untreated, this will eventually damage the periodontal ligament, loosening the tooth and causing further pain.
Specialist equipment is required to detect periodontitis affecting the cheek teeth. Early signs may include quidding, where the horse drops balls of semi-chewed long fibre such as hay or haylage, or halitosis (bad breath). A particularly stoical horse may show few clinical signs but may be unsettled when ridden.
A sedated oral examination in the very early stages can reveal subtle signs, allowing prompt treatment.
The author: Neil Townsend MRCVS is a specialist in equine surgery and dentistry, based at Three Counties Equine Hospital in Tewkesbury, Gloucestershire, which provides both an in-house and referral dentistry service. He also lectures on the subject, in the UK and internationally (tceh.co.uk).
Ref Horse & Hound; 19 March 2020
