When a young pet has teeth that are missing, and has no history of losing the teeth by previous accident or extraction, then there are 2 possible causes. Either the adult teeth never developed in these areas, or the adult teeth developed, but never erupted into the mouth.
Puppies and kittens develop their baby, or deciduous, teeth when they are a few weeks old. These teeth will remain in the mouth until they are replaced by the adult teeth, generally when the pet is 4-7 months old (sometimes later, in certain small breed dogs). In most cases when a young pet is missing teeth, the adult teeth just never formed in the bone in the areas where the teeth are missing. This has no significant impact on the health of the pet.
However, in some cases where there are missing teeth, the adult teeth are still present in the bone or underneath the gum tissue, and just never were able to grow up and out of the gum tissue and into the mouth. This can be caused by a heavy layer of connective tissue, called an operculum, which covers the teeth. The teeth may also be covered by a layer of bone. The teeth cannot penetrate this tissue. In other cases, the teeth have abnormally developed roots or are pointed in the wrong direction, which prevented them from erupting. And, there are some unerupted teeth that have no obvious cause, and seem to be a primary problem.
When teeth are missing, the only way to determine if a pet has unerupted teeth is to take a dental x-ray to confirm if the teeth are or are not present. If the teeth are present, and the pet is under the age of 10 months, there is a chance of the teeth being able to continue erupting if we remove the tissue that is blocking the advancement of the teeth. This is done by a surgical procedure in which the tissue over the teeth is removed by various methods, based on the type of tissue that is present.
If a pet over the age of 10 months has unerupted teeth, then there is minimal chance of those teeth being able to erupt, regardless of what work is done to “clear the path.” In this case, the unerupted teeth must be surgically extracted. If the teeth are left in place, the body often will ultimately reject the enamel of the unerupted tooth, and will form something called a dentigerous cyst. When this develops, we see a pet that develops a pale blue swelling in the mouth, near the area where the missing tooth is. In this case, surgery is always required, and becomes more complicated due to the destruction of bone and even adjacent teeth that can be caused by the developing cyst.
For dogs intended for the show ring or for breeding, missing teeth are a concern, because this can be a hereditary disorder. Certain breed qualifications will allow a maximum number of congenitally missing teeth, without creating a fault. For example, Dobermans can have up to 4 missing teeth, but any more than that is considered a fault. Again, each breed has its own specific qualifications regarding missing teeth.