Iyami's teeth are actually made of a rare metal which can be used for a variety of things.
Episode 6B: Iyami's Great Discovery
Main Article Episode 6B: Iyami's Great Discovery
The discovery of the metal is made in Episode 6B: Iyami's Great Discovery where Professor Dekapan finds out that Iyami's teeth are made of a rare metal that cost over ten billion yen, because of its elemental properties. It is named Iyametal after Iyami.
Iyametal would start being used all over Japan, but when the president of France asks him to supply Iyametal to the country of France he loses his last remaining tooth to a boy throwing a ball for his dad to catch. The tooth flies around to different hazards, but is finally stolen by a cat.
After Iyami is found out that he used cardboard to replace his teeth he never even steps on to French land is goes back under the bridge he lives in. Osomatsu and Hatabō decide to visit him, but when Iyami pushes Hatabō, Osomatsu hits Iyami in the back of the head forcing out a new set of teeth. Osomatsu then gives Iyami his hand, but is taken to the black factory where he is strapped into a chair and forced to produce Iyametal.
After Episode 6B: Iyami's Great Discovery Iyametal is never mentioned again.