“Double teeth” usually occur as a result of the baby teeth not being shed normally when the permanent teeth erupt. The permanent teeth usually come in between 3 and 7 months of age. If the baby tooth is not shed in an orderly fashion, this can lead to displacement of a permanent tooth into a painful position, or formation of pockets of infection at an early age. Usually the retained baby teeth can be extracted, making sure to remove the entire root.
There should never be two teeth of the same type in the same place at the same time. If you suspect that your pet has any double teeth they should be evaluated for possible problems.