Teeth (singular tooth) were bony structures found in the mouths of most species. They aided in chewing food and the speaking of their languages. They were typically cared for by the medical practice of dentistry.
According to Greek mythology, teeth from a dragon slain in war, if spread over a battlefield, would produce one warrior per tooth, each of which would then continue fighting. In 2376, this myth was conveyed to Captain Janeway of USS Voyager by her first officer Chakotay in the presence of Gedrin, a member of the Vaadwaur species. He was relating the dragon's teeth and their hidden potential to a long-dormant cache of armed ships Gedrin had led them to. (VOY: "Dragon's Teeth")
The Cardassian Bureau of Identification collected a tooth (the first molar) from all citizens of the Cardassian Union at the age of ten. It also collected the molars of non-citizens caught up in the Cardassian legal system. (DS9: "Tribunal")
Odo had no teeth, as he informed Makbar, the Chief Archon at Miles O'Brien's trial on Cardassia in December of 2370, when fulfilling the role of O'Brien's nestor during the proceedings. (DS9: "Tribunal")
Captain Benjamin Sisko referred to Klingon teeth as "fangs," and mentioned how he missed them after having his Klingon disguise removed. Odo disagreed, saying that he, for one, wouldn't miss the fangs at all. (DS9: "Apocalypse Rising")