Tooth
Teeth were part of the anatomy of most species. Its shape varied from the flat and short teeth of species such as humans, to the pointy teeth of species like the Futurekind, to the long, sharp teeth of species such as Prisoner Zero's. The humans of Silo 16 used this anatomical difference to differentiate between human and Futurekind. (TV: Utopia, The Eleventh Hour) Sharp teeth left "tooth marks". (TV: Mindwarp)
Upon his regeneration, the first thing the Tenth Doctor remarked on was his new teeth — "that's weird". (TV: The Parting of the Ways) River Song also remarked on her teeth immediately after one of her regenerations. (TV: Let's Kill Hitler)
Too much sugar could damage teeth; the Tenth Doctor didn't allow himself the rest of his Easter egg in favour of "keeping these teeth". (TV: Planet of the Dead) Toothbrushes were used to clean them. (TV: Mutant Copper) According to the Eleventh Doctor, food tasted weird after cleaning one's teeth. (TV: The Eleventh Hour)
Dentists took care of or healed people's teeth; when the First Doctor had a toothache, he had to seek dentist Doc Holliday to fix it. (TV: The Gunfighters) Sugar was detrimental to people's teeth. (TV: Planet of the Dead)
Max Capricorn had a gold tooth which, both in real life and in his advertisements, glinted when he said, "My name is Max." (TV: Voyage of the Damned)
References
"Hell's teeth" was an exclamation. (TV: Logopolis)
The expression "baring one's teeth" alluded to, in the words of the Eleventh Doctor, "talking up war", as both sides of the Cold War were doing. (TV: Cold War)
Queen Katryca's right hand man was named Broken Tooth. (TV: The Mysterious Planet)
