I begin with the Name of Allaah, the most Merciful, the One Who bestows Mercy

Praise be to Allaah. Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

It is not permissible for men to have gold teeth fitted unless that is essential, because it is haraam for a man to wear gold or adorn himself with it. With regard to women, if it is customary for women to adorn themselves with gold teeth, then there is nothing wrong with them doing that; a woman may plate her teeth with gold if it is customary for women to adorn themselves in this manner, and it is not extravagance, because the Prophet (peace and blessings of Allaah be upon him) said: “Gold and silk have been permitted for the females of my ummah.” 

If a woman dies in this state, or if a man dies who wore a gold tooth out of necessity, then it should be removed, unless there is the fear of mutilation of the corpse, i.e., there is the fear that the gum may be split, in which case it should be left alone. That is because gold is considered to be a kind of wealth, and wealth is to be inherited by the heirs of the deceased; leaving it with the deceased and burying it is a waste of money. 

From Majmoo’ al-Fataawa by Shaykh Muhammad ibn ‘Uthaymeen, 18/108.