An Old tooth can be found while digging at the digsite using a Trowel (obtained from the Varrock Museum or an Examiner, do not use a gardening trowel) on the digging area next to the animal skull. The dig area west of the animal skull also is confirmed to have the tooth. The archaeological expert says, "Oh, an old tooth. It looks like it has come from a mighty being. Pity there are no tooth fairies around here!"
You can trade this item with the Tooth Fairy in combination with other teeth, for a new pet, after Fairy Tale 3: Battle Of Orks Rift.