It is written in al-Mabsut, a fiqh book, that Imam Muhammad did not regard it objectionable to put on gold teeth or to plate the teeth with gold. 

Imam Azam regards gold teeth as makruh but putting on silver teeth or plating the teeth with silver as permissible. The reason why Imam Azam regards gold teeth as makruh is the fact that gold is a means of ornament and it is nor permissible for men. Then, if gold teeth are put on due to a medical necessity, there is no objection to it. As a matter of fact, it is known today that gold teeth are better than silver for dental health and that they do not cause stink.

The fake teeth that can be removed have to be removed while making ghusl. It is also better for cleanliness.