Prognathism refers to a condition wherein the lower jaw is longer than the upper jaw. Dog breeders refer to this condition as an overshot bite. The lower jaw supports the lower teeth and is the largest and strongest bone of the muzzle. All short-nosed (brachychephalic) breeds, including the Pug, Boxer, Bulldog, Boston Terrier and Pekingese have a prognathic occlusion pattern. The standards for brachycephalic heads allow or require prognathism. Some breeds, such as German Shepherd Dog, will go through a normal stage as puppies, in which the bite is overshot.3 One of the mild types of prognathism, level bite, refers to a condition when the incisors meet cusp-tip to cusp-tip rather than having the uppers overlap the lowers (scissor bite). Due to the abnormal incisor cusp-tip contact, all incisors will experience abnormal crown wear. Individual incisors will also experience a greater frequency of fracture than incisors with a scissor occlusion.
Brachygnathism refers to a condition in which an overbite, or overshot upper jaw exists. Both brachygnathism and prognathism are inheritable traits, passed from one generation to another. Although not life-threatening, these anatomic abnormalities can interfere with normal biting action and eating and can predispose to dental and jaw problems. Orthodontic correction of brachygnathism and prognathism can be utilized in select cases for medical purposes. Dogs suffering from a distinct overbite or underbite, unless normal for the breed, should be neutered to prevent propagation of these undesirable traits. The overshot bite may correct itself spontaneously in young puppies if the gap is no greater than the head of a wooden match.3
- Mordecai Siegal, Jeffrey E. Barlough. UC Davis Book of Dogs.
- Chris C. Pinney. The Complete Home Veterinary Guide.
- Debra Eldredge, Lisa D. Carlson, DVM, Delbert G. Carlson, James M. Giffin. Dog Owner's Home Veterinary Handbook.
- Localization of Canine Brachycephaly Using an Across Breed Mapping Approach