There are four variants of "Tooth" in RuneGuild; Small, Medium, Large and Giant. They can be obtained by killing monsters all around RuneGuild. When exchanged at one of the Tooth Chests at home, you can get skilling supplies, gp, clue scrolls and more.
Chests location
There are two chests to exchange your teeth, which are located just north of home teleport, on the either side of the building.
Tooth Lamb pet
If you're lucky, you could receive the Tooth Lamb pet when exchanging your tooth at the chest! Having the Tooth Llamb deployed when you loot the chest will give you twice the amount of loot for the same amount of tooth.