Eventually, by aging, neglect, overuse, or injury, teeth start to weaken and become more disposed to problems such as wear, decay, cracks, and discoloration. Consequently, covering the affected tooth or teeth may be needed for better appearance and tooth longevity. The affected tooth is prepared by removing the decayed part and restored by re-building its body for strength using a strong material. The outer layer of the tooth is reduced to allow space for the crown materials. An impression is taken and sent to the laboratory, where the technician is to fabricate the artificial crown using porcelain fused to metallic alloy or a porcelain substrate material. Sometimes a full cast metal crown is made for posterior teeth when durable strength is needed. The crown is then sent to the dental office for cementation on the prepared tooth with the proper cement material. While waiting for the technician to fabricate the crown, a temporary crown is formed to cover the prepared tooth.
In dentistry, an inlay is usually a restoration (filling) made of a solid material ( gold, porcelain, or ceramic substrate) and cemented to a prepared cavity in a tooth.
This procedure involves constructing the restoration outside of the mouth using the dental impressions of the prepared tooth sent to a laboratory for fabricating the inlay, rather than directly placing a filling material into the prepared tooth in the mouth. Similarly, an onlay is the same as an inlay, except that it includes a replacement for a missing tooth cusp by covering it.