The principles of tooth preparation include: 1. The tooth preparation should preserve the tooth tissue as much as possible, and the pulp should be kept healthy in living teeth. 2. The restoration made after the tooth preparation should ensure the health of the periodontal tissue, so it should be reasonably designed and reasonably prepared. 3. The restoration should meet the requirements of force resistance and retention after the tooth preparation, and should not be damaged by the occlusal force, but should be firmly in place and not easily dislodged by external forces. 4. The restoration should be able to restore the form and function of the tooth itself. Therefore, in clinical practice, it is important to master these principles when doing full crown restorations.