Abnormal Molar Wear in Horses

The most common forms of abnormal molar wear in horses include hooks, ramps, shear mouth, wave mouth, and step mouth. If left untreated, misalignment of the jaw due to these abnormal wear patterns may cause misalignment of the jaw, causing difficulty chewing, and abnormal incisor wear or abnormal molar wear elsewhere in the mouth.

Prognosis for all of these abnormalities is good if treated by a veterinarian promptly, and severe cases are entirely avoidable if teeth are floated on a regular basis as recommended by the vet. If dental malocclusions are not treated early enough, treatment may require multiple treatments to prevent exposing the root pulpits.

Some horses may not show any symptoms of dental pain or discomfort even when abnormal tooth wear is present. Due to this, regular dental examinations are important in order to catch and treat malocclusions early.

Hooks are one of the most common forms of abnormal wear in horse mouths. Caudal hooks involve elongation of the rear molar surfaces causing a point to form. Rostral hooks involve the front surface of the upper front molars elongating, forming a point and impeding lateral movement.

Similarly, ramps refer to overgrown front edges of the lower premolars.

Shear mouth entails sharp points forming on the upper molar cheek side and lower molars tongue side, due to extreme angulation of the chewing surface.

Step mouth occurs when a tooth is absent, and opposing molars are not ground down during chewing, forming a hill-like shape that extends into the gap left by the missing tooth. Step mouth is normally observed in horses post tooth extraction, or when permanent tooth eruption is delayed.

Wave mouth is caused by a combination of the above malocclusions, leading to a “wave-like” appearance of teeth. Wave mouth is uncommon, as a large number of teeth malocclusions are involved in creating this pattern.

Abnormal molar wear occurs due to impeded or insufficient wearing of the molars, resulting in overgrown sides or uneven chewing surfaces of the teeth.

Risk factors for abnormal dental wear include;

• Jaw misalignment (overbite, underbite)
• Missing teeth (extractions, delayed eruption of adult teeth)
• Improperly reduced teeth (opposing tooth was not properly corrected)
• Age (higher incidence in horses between 2 - 5 years due to softer teeth and higher risk of maleruption problems)
• Diet
• Lifestyle (stabled horses at higher risk due to softer foods and lack of grazing)
• Pre-existing dental conditions (abnormal incisor or molar wear)

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

Diagnostic tests include;

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

Typically abnormalities are quickly remedied during a routine dental float. Severe conditions may require specialized diets or multiple treatments spaced 12 to 18 months apart, as teeth can only be reduced a certain amount before exposing the root pulps. In severe cases floating may not be curative and a specialized diet is prescribed.

Abnormal tooth wear can not correct itself, and if untreated can lead to increasingly severe dental or oral damage. When treated by a veterinarian outcomes are favorable, and regular maintenance is recommended even without a history of malocclusions. Horses that develop wave complexes have a poorer prognosis, and may require extensive treatment over long periods to correct the abnormality.

Uneven molar wear is preventable through routine dental care and regular floating. Floats are recommended on an annual or bi-annual basis depending on factors such as horse age, diet, and health history.

Even wearing of molars can be encouraged by increasing grazing time, and feeding horses from the ground as opposed to in elevated feeders. These behaviors encourage more chewing, allowing for more consistent molar wear.

Abnormal molar wear is not contagious.

Uneven tooth wear is normal in horses, causing points to form on the outer side of upper teeth and the tongue side of the lower teeth. Conditions such as wave mouth, shear mouth, step mouth or tooth hooks are abnormal. These conditions are secondary to pain, missing or damaged teeth, and misalignment of teeth or jaws.

Dental flotation