The Olsen twins did wear dentures on Full House when playing the roles of Michelle tanner.
The reason the Olsen twins wore dentures on Full House is because they had lost their baby teeth at different times.
So the Olsen Twins wore dentures to be sure that their teeth always matched when they switched between the scenes.
Because the Olsen Twins baby teeth came in at different times the show Full House needed to use dentures to maintain the consistency between the scenes for the two actresses.
The Olsen twins had to be fitted with fake teeth to play the toothy Michelle Tanner on Full house.
Because Mary Kate and Ashley are fraternal twins they didn't lose their baby teeth at the same time.
As they've aged, their also nearly imperceivable variations have also become even slightly more pronounced.
At one point, you see them with missing two front teeth.