Praise be to Allah.
Firstly: It should be noted that it is not permissible to have a gold tooth unless there is a need for that. It is not permissible for anyone to have a gold tooth made for adornment except for women; if it is their custom to adorn themselves by covering their teeth with gold then there is nothing wrong with that. But in the case of men that is not permissible, unless there is a need for that.
Secondly: If a person who has gold teeth dies, then if it is possible to remove the tooth without mutilating him, then it should be removed, because his possessions are to be transferred to his heirs. If it is not possible to remove it without mutilating him, such as causing the rest of his teeth to fall out, then it should be left and buried with him.
If the heir is an adult of sound mind and he allows that, it should be left alone. Otherwise the scholars have stated that if he thinks that the deceased has disintegrated, the grave may be dug up and the tooth recovered, because leaving it there is a waste of money and the Prophet (peace and blessings of Allaah be upon him) forbade that.