Malocclusion of Teeth in Dogs

Normally, a puppy will have 28 baby teeth once it is six months old. By the time it reaches adulthood, most dog breeds will have 42 teeth. A misalignment of a dog's teeth, or malocclusion, occurs when their bite does not fit accordingly. This may begin as the puppy's baby teeth come in and usually worsens as their adult teeth follow.

The smaller front teeth between the canines on the upper and lower jaws are called incisors. These are used to grasp food and to keep the tongue inside the mouth. Canines (also known as cuspids or fangs) are found behind the front teeth, which are also used to grasp. Behind the canines are the premolars (or bicuspids) and their function is to shear or cut food. Molars are the last teeth found at the back of the mouth and they are used for chewing.

Symptoms and Types

Common problems that can arise from malocclusion:

• Mouth injuries
• Periodontal disease
• Soft-tissue defects from tooth contact in the floor of the mouth and the roof of the mouth (palate)
• Wear on the teeth
• Fractures

If problems with the palate persist, a fistula may result and become infected. In cases of misaligned teeth (or malocclusion), the dog may have difficulty chewing, picking up food, and may be inclined to eat only larger pieces. They are also prone to tartar and plaque build-up.

There are several types of diagnosable malocclusion:

• Overbite (sometimes called overshot, Class 2, overjet, or mandibular brachygnathism)
• Underbite (also called undershot, reverse scissor bite, prognathism, and Class 3)
• Level bite (sometimes called even bite)
• Open bite (front teeth don’t meet each other when mouth is closed)
• Anterior crossbite (canine and premolars occlude normally but one or more lower incisors are in front of the upper incisors)
• Posterior crossbite (one or more premolar teeth overlap the upper teeth)
• Wry mouth or bite (one side of jaw grows longer than the other)
• Base narrow canines (lower teeth protrude inward and can harm the upper palate)

The tips of the premolars (the teeth right behind the canines) should touch the spaces between the upper premolars, which is called the scissor bite. However, it is normal for flat-faced breeds (brachycephalic) such as Boxers, Shih Tzus, and Lhasa Apsos not to have scissor bites.