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.
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 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 overcrowding. 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.
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 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 wry bite 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, is located at 9111 Taft Street, Pembroke Pines, Florida. (954) 432-1111. Reformatted from the original on Netvet..