E Q U I N E D E N T I S T RY — A N I N T R O D U C T I O N
1
Welfare
The prevention and correction of dental abnormalities is critical to the welfare of the horse. Due to aspects of
their anatomy all horses require regular dental care regardless of age or use as if untreated they will develop
severe, painful and potentially life threatening problems. Due to the difficulty in assessing a horse’s oral cavity
many horses suffer for prolonged periods because of the failure of anyone to recognise that there is a problem
“out of sight, out of mind”.
Signs of dental disease
Halitosis or bad breath is a sure sign of dental disease; it indicates the presence of harmful bacteria and is
associated with gingivitis and periodontal disease (gum disease). The presence of plaque on teeth also indicates
dental disease and requires treatment. In any horse suffering weight loss, choke colic or diarrhoea dental disease
should be on the list of differentials. By observing a horse eat a lot of information can be obtained. Signs of
dental disease when eating include the spilling of feed, washing the mouth after eating, excess salivation, eating
either faster or slower than is normal, packing feed in the cheeks, abnormal jaw movements, tilting the head
and dropping balls of feed. (This is not an exhaustive list).
In the ridden horse signs of dental disease include poor collection, chewing of the bit, tail swishing and aggressive
behaviour such as rearing, bucking or kicking, resistance in one or both directions, placing the tongue over the
bit and opening the mouth. (Again not an exhaustive list).
Remember to consider dental problems for horses showing signs of unacceptable behaviour, many of these horses
exhibit these behaviours in response to pain.
Anatomy
Clinically relevant anatomy
The innervation of the dental arcades and their immediate surrounding structures is supplied by the trigeminal
nerve, the fifth cranial nerve. This nerve exits the cranium below the ear and progresses cranially, dividing into
the maxillary nerve and mandibular nerve. Blood supply to the equine tooth is still not fully understood but is
supplied via pulp canals entering the tooth at the apical foramen. Vessels of note include the greater palatine
artery which lies on the lateral borders of the hard palate and communicates with both internal maxillary arteries,
rupture of this artery can lead to severe haemorrhage. The muscles of mastication are the paired lateral muscles
from the maxilla and cranium to the mandible, these are the masseter and temporalis muscles that close the jaw
and pull to the side. The medial pterygoideus muscles also close the jaw.
The muscles responsible for the opening of the jaw are the digastricus geniohydeus, and the genioglossus coupled
with the sternohyoideus and omohyoideus. The muscles of the cheeks and lips are supplied by the facial nerve,
the seventh cranial nerve and consist of the levator depressor, labii maxillaris and mandibularis, the orbicularis
oris, the incisivus mandibularis and maxillaris, the buccinator and zygomaticus muscles. These muscles control
the functions of lip closure, elevation, retraction, and depression as well as flattening of the cheeks. Motor
innervation of the tongue is provided by the hypoglossal nerve, cranial nerve twelve.
Equine teeth are comprised of three tissues enamel, cementum and dentine; equine teeth are hyposodont
or long crowned teeth, with the long reserve crowns embedded in the deepened alveoli. Horses are anosignathic
the distance between the maxillary cheek teeth rows is a median 23% wider than that between the mandibular
rows, a feature that is termed anisognathia. This is in comparison with human teeth that are isognathic or equally
spaced.