Sometimes removing tooth decay effectively requires the removal of a portion of your tooth. The removed portion is then replaced with a porcelain inlay or onlay. Your dentist customizes an inlay or onlay to fill the space left behind when a portion of your tooth is removed. Traditionally, inlays and onlays were made out of metal, much like traditional filings. Now, porcelain-milled inlays and onlays are virtually indistinguishable from natural teeth and provide relief from chewing pain, cavity pain, and tooth degeneration.