Puppies typically have 28 baby teeth and 42 adult teeth. Outside causes can contribute to malocclusions, and genetics plays a role in many cases.
Genetics are responsible for tooth bud position; malocclusion can pass from mother to puppies. For example, tooth overcrowding is common in small breeds, and overcrowding and underbites are common in brachycephalic breeds, such as boxers, Boston terriers, pugs, bulldogs and other short-snout breeds. Lingually displaced mandibular canines occur when the lower canines push into the hard palate. Outside factors can contribute to this condition, but genetics plays a large role, especially in German shepherds and Rottweillers. Mesioversion of the maxillary canines, also known as lance canines, causes the upper canines to point forward. This condition is common and genetic in Shetland sheepdogs. Because of a probable genetic connection to malocclusion, removing affected dogs from the breeding pool is recommended.