Teeth and Bite Genetics
Heredity of teeth and bite is mostly unknown and presents a confusing pattern. That is, it is mostly unknown if it is dominant, recessive or polygenic for each abnormality. However these teeth and bite faults can be seen with a simple visual inspection by the age of 1, which means that affected dogs can easily be kept from breeding. The most commonly seen issues in dogs are missing teeth (in the Mudi usually P1 and P2), fused teeth (does occur rarely in the Mudi), oligodontia (absence of most if not all teeth, not seen in the Mudi), overbite/overshot bite (occurs rarely in the Mudi), retained deciduous teeth (baby teeth do not fall out by themselves, this is seen to occur rarely in the Mudi), extra teeth (rarely occurs in the Mudi), underbite/undershot bite (occurs rarely in the Mudi) and wry mouth (or wry nose or jaw, occurs rarely in the Mudi).
Dogs with brachycephalic skull type (Bulldog, Boxer) frequently have imperfect dentition as does at least one hairless breed (Chinese Crested).
Studies of dentition done by Willis with German Shepherds, were not indicative of any simple mode of inheritance. Willis also reported that the difficulty of identifying the heredity of missing teeth is compounded by the fact that apparently missing teeth are sometimes present below the gum rather than totally absent. It is his opinion that faulting individuals for such a trait with such poorly understood inheritance may be dangerous in that the dogs otherwise outstanding qualities may be discarded from a breeding program.
Abnormal bites vary in levels of severity. Some breeds and some lines within breeds appear to have a higher incidence of bite faults than others. It is seen that some lines or individuals do produce more incorrect bites than breed averages, leading to a general familial inheritance pattern. Some researchers have suggested that the shortening of the lower jaw and muzzle might be responsible for incorrect bites and missing teeth. It has been observed that dogs with undershot bites usually have parents with scissors bites, suggesting that the trait is recessive, but this was not proven to be the case by Whitney.
Upper and lower jaw structure appear to be independently inherited traits and even the size of the incisors may play a role in occlusion. Abnormal size and overly vertical incisors can create incorrect bite. The growth of the lower jaw may not parallel the rest of the head.
Puppy Bite Information
In general, a puppy's bottom jaw will continue to grow until they are approximately 9 months old, which means the bite is in transition until 9-11 months of age. It should be noted that the top jaw is also in transition and growing during this period. The bite can go either way, from scissors to underbite or from scissors to overbite, or from scissors to level bite. It is a general observation in some breeds that a puppy which starts off with an overbite, even if it corrects later on, can have a higher incidence of producing more puppies with overbites. Puppies with underbites almost never correct themselves.