Reference: Fataawa Muhimmah li-Nisaa. al-Ummah – Page 40
Question: If a person wears dentures (false teeth), is it obligatory upon him to remove them when rinsing the mouth [during wudhoo]?
Response: If a person wears dentures, then that which is apparent is that it is not obligatory upon him to remove them, [since this] resembles the [issue concerning wearing a] ring; and it is not obligatory to remove the ring when making wudhoo, rather, it is better to move it [around], but [even] this is not obligatory because the Prophet (sal-Allaahu ‘alayhi wa sallam) used to wear [a ring] and it has not been transmitted [from him] that he used to take it off during wudhoo. And this is the most apparent [of the opinions] since the [false] teeth prevent the water reaching [all parts of the mouth], especially since some people experience much difficulty in removing them and then [afterwards] replacing them.