Retained Deciduous Teeth
When deciduous or baby teeth are between four and six months of age, they are normally pushed out of the mouth by erupting adult teeth. Occasionally, an adult tooth erupts next to the deciduous tooth, dislodging it into an abnormal location. You will notice two teeth where one should be. This occurs most commonly in toy breeds such as Maltese and Yorkshire terriers.
In this case, remove the deciduous tooth so the adult tooth can have sufficient room to erupt properly.