If you have a tooth that is partially damaged, a dentist can offer a number of different restorative options. In many cases, dental crowns are used to restore a tooth that has been damaged, or to address cosmetic issues. However, if a tooth does not warrant a whole crown, a dental onlay is used. A dental onlay is similar to an inlay, which is similar to a filling for your tooth.Dental onlays are used to replace the cusp of a tooth. The cusp refers to the top points on the tops of the teeth. For people who struggle with bruxism, or teeth grinding, the cusps of the teeth can be worn down or damaged. If a tooth is only partially damaged due to bruxism, it may make sense to just use an onlay instead of a crown. Similar to crowns, onlays are usually made of porcelain. Less of an existing tooth needs to be removed to prep a tooth for a porcelain onlay versus a porcelain crown.