"Benifits of inlays and onlays over metal fillings"

1. Metal fillings requires more of the natural tooth to be drilled out even if it isn’t decayed so that the tightly packed amalgam will stay put.
2. Additionally with time metal fillings tend to become loose and can even fall out.
3. With inlays and onlays more of the natural tooth can be preserved, since the porcelain will be bonded to the tooth rather than packed into a space.
4. The porcelain of inlays and onlays is matched to your tooth color so more esthetic.
5. Porcelain doesn't conduct heat so there are no worries about hot and cold sensitivities to food and beverages.

Source :- "Benifits of inlays and onlays over metal fillings"