Crown restorations are generally used as metal porcelain crowns, all-porcelain crowns or metal crowns for posterior teeth after root canal treatment to restore the shape of the posterior teeth and reinforce the remaining dental tissue; or crown restorations for aesthetic purposes in the anterior region. A characteristic of crown restorations is that they are placed over the natural teeth and have a migrating contact zone with the natural teeth near the gums, which is the main location where problems with crown restorations occur. Crown restorations maintenance precautions: a. Normal diet, but avoid using teeth to bite too hard things, such as using the back teeth to get high on pine nuts, hazelnuts, eat iron fava beans, open the cap of a beer bottle with teeth. The cleaner the crown restoration is brushed, the longer it will last and will not be damaged by brushing. Crown restorations are prone to problems and how to deal with them: a. The most common crown off bonding, that is, the crown fell off, please put away the crown, try to go to the original restorer or any dentistry within a week for re-bonding; such as crown off more than two weeks is likely to tooth displacement, the need to re-produce the crown restoration. Second, food embedment, after the crown is made, there is food embedment between the crown and the adjacent teeth, please remove the embedment after each meal using dental floss, and return to the clinic as soon as possible to make fine adjustment of the tooth shape to solve the food embedment; for severe embedment excluding other reasons based on the crown may need to be re-made. Third, the porcelain layer of porcelain crown loss, that is, often said chipped porcelain, the need for physicians to re-production or use resin repair according to the situation. Fourth, the gingival margin gray line, unsightly. Traditional metal porcelain-type crowns, the gingival margin has a greater chance of deep staining, and the natural teeth differ greatly, unsightly, so that it is necessary to re-fabrication, choose a more beautiful all-porcelain crown restoration.