There are two basic types of porcelain fillings, inlays and onlays, which are also known as “indirect” fillings. Both types are painstakingly crafted to fit precisely in the space from which damaged tooth structure has been removed. The primary difference between inlays and onlays is that the former is crafted to fit inside an area of decay while the latter is laid atop the tooth, covering its cusps. The porcelain used in either restoration is strong enough to preserve the health of your remaining tooth while maintaining the appearance of your smile.A dental inlay or onlay is made from porcelain; a porcelain inlay or onlay is virtually invisible, and modern porcelain is extremely strong and durable. These dental fillings can look beautiful. Alternatively, an inlay or onlay may be made from high-quality precious metal alloy polished to a soft sheen.