Puppy teeth (or deciduous teeth) start breaking through around three weeks, and are replaced with an adult set of teeth at about 4-6 months. Most dogs will ultimately end up with 42 adult teeth, including 10 molars in the very back, 16 premolars in the middle, 4 large sharp canines, and 12 small incisors in the front. Although if you have had a teething puppy it sometimes feels like a lot more.
As your puppy reaches the appropriate age, their adult teeth will begin to form from tooth buds. These tooth buds are found in the upper and lower jaw bones. As these tooth buds grow and the adult teeth get bigger they begin to press on the roots of the baby teeth. This stimulates the body to begin resorbing the roots of the baby teeth. As the adult teeth grow even larger they will eventually push out what remains of the baby teeth. The adult tooth then has room to break through the gums and take the place of the baby tooth.
In some cases the root of the baby tooth is not resorbed properly and therefore cannot be forced out of the mouth by the erupting adult tooth. In these situations the adult tooth usually erupts through the gums very close to the retained deciduous tooth, in an abnormal position. This often causes an abnormal bite resulting in pain and difficulty chewing and eating. Even if your pet does not appear to be bothered by the extra teeth, the overcrowding almost always causes excess plaque buildup leading to gingivitis.
The most commonly retained deciduous teeth are the canines, although this condition can happen with any of your dog’s deciduous teeth. Small dogs and brachiocephalic breeds (breeds with pushed-in faces) are also more prone to this condition, though it can happen in any size or breed.
The only effective treatment for retained deciduous teeth is surgical extraction. Removing the extra baby tooth as soon as you notice it is still there after the adult tooth has erupted offers the best chance that your dog’s adult tooth may be able to move into its proper place. Leaving the deciduous tooth in your dog’s mouth for too long can negatively impact their surrounding teeth, potentially causing infection or necessary extraction of multiple surrounding teeth due to improper positioning or decay.