Conclusion By adopting the root canal therapy together with the technologies of inner bleaching and seal dentinal tubule we can prevent and cure crown surface discoloration effectively.

Done root canal treated teeth, dentists will advise the Crown usually set up and finished the treatment of teeth, tooth mass amount of reservation, also affect whether column needs to be done.

Objective: To evaluate the relationship between crown defect types and crown fractures of root-canal-treated mandibular molars.