I just need a ruling about getting a gold crown from the dentist.
It has no allergic reactions. The other option is nickel but there is a possibility of allergies.
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
It will be permissible to get a gold crown. Imam Abu Hanifah explained that if silver used in the mouth will result in a problem, such as bad breath, then using gold will be permissible. Since there is a good reason for that, it is not considered to be wearing the gold for adornment.
Only Allah knows best
Written by Maulana Mustafa Umar
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Fataawaa Mahmudiyyah 5:218