Name that Bite . . .

by Dr. Jan Bellows, D.V.M.

Diplomate American Veterinary Dental College

Diplomate American Board Veterinary Practitioners

What is really meant by the words: Overbite, open bite, overjet, level

bite, overshot, underbite, anterior crossbite, wry bite, retained deciduous

teeth, base narrow canines? Breeders, show judges, veterinarians and others

who want to express specific dental conditions in dogs and cats need to use

the proper terms. This article will review commonly used and misused words

to describe tooth alignment.

Anatomy

Dogs normally have twenty-eight deciduous (primary or baby) teeth that

erupt during the first six months of life. Most breeds have forty-two adult

teeth. Cats have twenty-six deciduous and thirty adult teeth. There are four

types of teeth. Incisors of are the smaller teeth located between the

canines on the upper and lower jaws. They are used for grasping food and help

keep the tongue within the mouth. Canines (also called cuspids or fang

teeth) are located on the sides of the incisors and used to grasp food.

Premolars (bicuspids) are for shearing or cutting food and are located

behind the canines. The molars are the last teeth in the mouth. They are

used for grinding nourishment for entry into the esophagus.

Missing or Extra Teeth

Dogs and cats are frequently born without the proper number of teeth.

Extra (supernumerary) teeth can cause periodontal disease from over

crowding. The American Kennel Club sets the standards concerning minimum

number of teeth for each breed of dog that can be shown. Dental x-rays can be

safely taken as early as ten weeks of age to evaluate if the correct number

of adult teeth will emerge. This is recommended as a part of the prepurchase

examination in certain breeds. Usually missing teeth will not cause an

eating problem.

Occlusion

The way teeth align with each other is termed occlusion. Normal

occlusion in most breeds consists of the upper (maxillary) incisors just

overlapping the lower (mandibular) incisors (scissor bite). The lower canine

should be located equidistant between the last (lateral) incisor and the

upper canine tooth. Premolar tips of the lower jaw should point between the

spaces of the upper jaw teeth. Flat faced breeds (Boxers, Shih-Tzu, and

Lhasa Apso) normally do not have scissors bites.

Malocclusion

Malocclusion refers to abnormal tooth alignment. Overbite (overshot,

class two, overjet, mandibular brachygnathism) occurs when the lower jaw is

shorter that the upper. There is a gap between the upper and lower incisors

when the mouth is closed. The upper premolars are displaced at least

twenty-five percent toward the front when compared to the lower premolars.

An underbite (undershot, reverse scissor bite, prognathism, class 3) occurs

when the lower teeth protrude in front of the upper jaw teeth. If the

upper and lower incisor teeth meet each other edge to edge, the occlusion is

an even or level bite. When the upper and lower incisors do not overlap or

even meet each other when the mouth is closed, the pet has an open bite.

Anterior crossbite occurs when the canine and premolar teeth on both sides

of the mouth occlude normally but one or more of the lower incisors are

positioned in front of the upper incisors. Anterior crossbite is the most

common malocclusion, is not considered genetic or hereditary and is

correctable. If there is an anterior crossbite there must be a condition

termed posterior crossbite. Posterior crossbite occurs when one or more of

the premolar lower jaw teeth overlap the upper jaw teeth. This is a rare

condition that occurs in the larger nosed dog breeds. A wry mouth or wrybite

occurs when one side of the jaw grows longer than the other. It is

considered hereditary and difficult to correct. Base narrow canines occur

when the lower canine teeth protrude inward and can damage the upper palate.

Often this condition is due to retained baby teeth and can usually be

corrected through inclined planes used to push the teeth into normal

occlusion.

Dr. Jan Bellows is one of the thirty veterinary dental specialists in the

country recognized by the American Veterinary Medical Association. His

office, All Pets Dental Clinic located at 9111 Taft Street, Pembroke Pines,

Florida. (954) 432-1111.