Abnormal Incisor Wear in Horses

Abnormal incisor wear is commonly due to hereditary jaw misalignment, molar malocclusions, missing or delayed eruption of teeth, cribbing, or uneven chewing patterns.

Abnormal incisor wear is uncommon and is quickly corrected if treated early. Horses experiencing difficulty chewing due to abnormal wear may lose weight, so prompt veterinary examination is recommended for any horse showing symptoms of abnormal wear.

Horses with abnormal tooth wear may not show any symptoms indicating pain. As a result, regular oral exams from a veterinarian are important to address these conditions early.

The most common types of abnormal wear are ventral or dorsal curvature, underbite, overbite, and diagonal bite.

Overbites involve the upper incisors protruding past the lower teeth.

Underbites are the opposite; lower incisors are further forward than the upper teeth.

Diagonal bite occurs due to one side of the jaw having overgrown lower incisors, while the opposing side has overgrown upper incisors leading to a slanted appearance from the front.

Ventral curvature involves the corner lower incisors growing too long, with the opposing teeth being too short allowing appearance of the teeth to curve upwards like a smile, whereas dorsal curvature involves the upper incisors growing too long causing a frown-like curvature.

Abnormal wear typically occurs due to the typical figure-eight pattern of chewing being interrupted or impeded. Abnormal incisors can also be secondary to cribbing or wood chewing.

Potential risk factors include;

• Congenital jaw misalignment (overbite, underbite)
• Pre-existing abnormal dental wear (hooks, ramps, shear mouth, wave mouth)
• Missing teeth (tooth extractions, retained deciduous caps)
• Old age causing expiry of teeth

Diagnostic tests on horses are commonly performed under sedation, to allow thorough examination of the mouth.

Diagnostic tests include;

• Physical examination
• Oral examination with use of an oral speculum

Treatment typically involves a dental float to correct the abnormality. In severe cases, multiple floats over periods of months to years may be required in order to fully treat the condition without causing damage to the tooth pulps.

Severe cases of congenital overbites (parrot mouth) or underbites (sow mouth) may require corrective surgery.

Abnormal incisor wear is not self-correcting, and progresses until treated by a veterinarian. Minor abnormalities are commonly remedied with a single treatment, but more severe conditions such as a diagonal bite require frequent corrections. Regular maintenance is recommended for horses regardless of their dental history.

Abnormal wear is preventable by receiving routine dental floats during annual or bi-annual checkups. Discouraging or interrupting cribbing can help prevent ventral and dorsal curvatures, as well as diagonal bite. Restricting a horse’s access to wood they may wish to chew on can also prevent curvatures and diagonal bite.

Severe congenital overbites and underbites can be prevented through selective breeding, but once a horse has developed these conditions they may require corrective surgery.

Abnormal wear is not contagious.

Abnormal incisor wear is uncommon and often secondary to other dental or behavioral problems.

Dental flotation