Hyperdontia's the condition of having supernumerary teeth, or teeth which appear in addition to the regular number of teeth. Types The most common supernumerary tooth's a mesiodens, which's a mal-formed, peg-like tooth that occurs between the maxillary central incisors. Fourth and fifth molars that form behind the third molars are another kind of supernumerary teeth. Another rare type of supernumerary teeth's a "third set of teeth" that forms underneath and pushes out the second set of teeth, m… (More on Hyperdontia)