When you have metal dental work in your mouth, one possibility is that you can have an allergy to that metal. This will cause chronic inflammation around that dental work.
Many people are allergic to nickel. Often the allergy becomes noticeable with earrings and people will need to get non-allergenic earrings, made without nickel.
Nickel is a component of some alloys used for dental crowns and removable partial dentures. If you have a sensitivity to nickel, you will experience a chronic inflammation around these crowns or partials.
Nickel is also present in some dental posts or dental pins that are used in teeth with root canal treatments, to help strengthen the tooth and retain a dental crown. Most metal posts these days are made out of titanium, which is a very bio-compatible element, but posts with nickel in them are still available. Some may argue that a post inside a tooth will not provoke any allergic reaction, but the tooth root is porous, and molecules of corrosion products of metals inside the tooth can easily seep through the tooth, given enough time.
Allergy to dental amalgam, an alloy of silver, mercury, and small amounts of tin, copper, and/or zinc, is very rare, but instances have been reported. We are not aware of any documented allergies to precious metals such as gold and platinum.