Crown margins do not fit together generally due to cementation failure or insufficient retention of the restoration, the treatment method for re-cementation or redesign of the retention shape, as follows. 1. Re-cementation: Because of improper selection of cement or improper cementation procedures, resulting in crown margins do not fit together, you can remove the residual cement after removing the crowns, and the cemented surfaces are routinely processed, and a high-quality cement is selected for re-cementation. 2. Re-design of cementation: Because of insufficient cementation of the restoration, the restoration is shifted during mastication, resulting in poor edge fit, the restoration should be re-designed and prepared for dentistry and then fabricated into a new restoration. It is recommended to go to the hospital in time to receive professional treatment.