Occlusal Evaluation in Dogs
Genetic counseling for breeding pairs involves an occlusal evaluation and determination of whether any abnormalities are likely to be passed on to potential offspring.
CRITERIA UTILIZED FOR BITE DETERMINATION:
- Tooth Position - The upper incisors should overlap the lower incisors in what is called a “Scissor Bite.” The lower canine teeth when the jaws are closed should be equidistant to either the upper canine or upper lateral incisor. The four premolars in the lower jaw should be one tooth in front of their counterpart in the upper jaw so that when the jaws are closed there should be a “zig zag” open space that is visible.
- Facial symmetry - If you draw an imaginary line along the midline of the face the bone structures on either side should be apparently equal in size and form. The midline of the dental arches should equally separate the two upper and lower central incisors.
- Numbers of Teeth - In the Mesocephalic breeds like German Shepherd, and Dolichocephalic breeds like Collies , the normal number of teeth is 42 adult teeth. Missing teeth, that are not radiographically visible, are a genetic fault.
Bite Evaluation
Bite evaluation involves the study of an animal’s occlusion or how the teeth erupt and their position to each other when the jaws are closed. This can be developmentally altered or be predetermined genetically. In the case of teeth that have developed into improper occlusion from adult teeth malerupting, the underlying cause might be jaw trauma that affects the position of the young tooth bud. This subsequently erupts into an inappropriate position or becomes embedded and not visible due to the axis of eruption being disturbed. In addition to trauma, retention of baby teeth can cause adult teeth to erupt into an abnormal position due to the deciduous tooth’s root guiding the adult in it’s emergence into the wrong position
Genetic Considerations
Unlike developmental problems causing individual teeth to be misaligned causing faulty occlusions, genetic causes for tooth positioning involve the jaw growth which dictate the position of the teeth. Like hip dysplasia, which has many genes (polygenic) coding for bone development, the jaw growth is often controlled by genetic forces. These genetic controls are inherited and often passed from one generation to another. For breeding animals in which good-to-perfect bites are important aesthetically and in the show ring, malpositioned teeth, due to genetics, can impact both the health of teeth and the soft tissue around them.
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