Use chairside Computer-Aided Design & Computer-Aided Manufacturing(CAD/CAM) system (computer aided design / manufacture), using glass ceramic zirconia enhanced lithium silicate glass ceramics (VITA, SUPRINITY, VS) material, compare the difference of firmness, comfort and durability between two kinds of root canal restoration methods:endocrown and 90° shoulder endocrown. Objective to establish the optimal method and material for the restoration of the teeth with root canal therapy.

Inclusion Criteria:

1. 18-60 year old patients with healthy body, the tooth is molar, root tip no obvious damage, no root fracture by X-ray;
2. after complete root canal therapy, the remaining 4 wall intact tooth tissue;
3. after complete root canal therapy, the remaining 3 wall intact tooth tissue;
4. have good oral hygiene habits;
5. agreed to participate in the trial and signed the informed consent form;
6. patients who are not participating in other clinical trials;
7. after completion of the repair, compliance with the USPHS evaluation criteria of marginal density class A cases

Exclusion Criteria:

1. obvious destruction of the apical tissue and large cysts;
2. severe periodontitis patients;
3. oral malignant tumor patients;
4. radiotherapy patients;
5. pregnant women;
6. patients with mental illness or systemic diseases;
7. people who can not take care of themselves;
8. the researchers believe that is not suitable for the test.