Malocclussion

Description

Both undershot jaw and overshot jaw are conditions of malocclusion. A malocclusion is an improper meeting of upper and lower teeth that can interfere with a horse's ability to masticate feed. A malocclusion often results in poor digestion, and, in some cases, malnutrition because the horse has trouble eating or grazing and cannot chew feed well enough for good digestion.

Both undershot and overshot jaw are usually inherited. Many horses have slight malocclusions and the problem is serious only when the misalignment is so pronounced that the horse cannot graze and chew effectively, resulting in uneven wearing of the teeth and other dental problems.

When the conditions are evident in a young horse, they usually become worse as the horse grows and matures.

Symptoms

• Misalignment of top and bottom jaws
• Inability to masticate feed properly
• Need for frequent dental care because teeth do not wear evenly
• Teeth grow too long and form sharp hooks that can damage cheeks and/or gums
• Reluctance to eat
• Malnutrition

Causes

Both undershot jaw and overshot jaw are hereditary.

Prevention

Careful selection of breeding stock is the best prevention of these conditions.

Treatment

Treatment of both undershot jaw and overshot jaw works best if detected by the time the horse is six months old. Wire tension bands from the upper incisors to the first maxillary cheek teeth to slow the growth of the upper jaw sometimes works well to correct overshot jaw. A veterinarian can devise a treatment based on the conformation of the horse's jaws. If braces are required, they may need to be left in place for several months. Careful monitoring is necessary to make sure no adverse effects occur.