Crowns after root canal treatment usually do not require grinding of both sides of the tooth, but only need to do crown restoration after grinding the tooth with root canal treatment smaller. Clinically, after root canal treatment, the tooth often has a large body defect, and because the nerve has been killed and taken out, the tooth loses its nutrient supply, and its brittleness increases. Therefore, it is recommended that the tooth with root canal treatment should be restored with a porcelain crown or an all-ceramic crown, so as to protect the foundation tooth and prevent the tooth from losing its retention value due to longitudinal fracture of the crown. Generally after root canal treatment, crowns are made on the original abutment teeth, only need to grind out the teeth evenly according to a certain ratio except for a part of the teeth, and then use the box-type retention force and the role of adhesive to make the crown fixed on the abutment teeth, some of the teeth with excessive defects can be enhanced by playing the fiber piles to enhance the retention, and therefore do not need to pass through the two sides of the teeth.