Compare the comfort and durability of Ceramic (VITA,Suprinity ,VS) vs Resin Bloc (VOCO, Grandio Bloc,GB) Endocrown by chairside CAD/CAM system (computer aided design / manufacture).

Objective:To provide information of material selection for the chair-side restoration of the teeth after root canal treatment.

Pulpal and periapical diseases are the main causes of tooth loss. Root canal treatment (RCT) is the only effective way to treat these diseases. However, failure of RCT is commonly seen without coronal restoration.Endocrown is a new type of onlay with a retainer in the pulp cavity which consists of a cervical margin in the form of a butt joint and a preparation of the pulp chamber.This restoration method is not only good at the preservation of residual tooth tissue, but also suitable for severely damaged molars or premolars after dental pulp treatment.More and more endondontist tend to use this ways because they are a minimally invasive solution in such cases.Endocrown is mainly made of glass-ceramics, which has the advantages of beautiful appearance, high hardness and good biocompatibility. However, ceramic materials are brittle and fracturable, and need to be sintered twice in the manufacturing process, which is relatively complex and time-consuming. Composite resin block material is a new type of composite material developed in recent years. It is used for chairside CAD/CAM restoration,It has beautiful and natural color, and its elastic modulus is close to dentin. Therefore, it is more compatible with natural teeth in performance.Moreover, In the process of making, the steps of secondary sintering and glazing are omitted and shortened. But, there was no sufficient data to verify which material was more effective. The main aim of this trial is to compare the clinical efficacy of ceramic vs resin-based bloc endocrown. Other objectives include looking for the prognostic and influence factors of the related effects.

Inclusion Criteria:

1. The patient is healthy and is 18-75 years old and has molar teeth and tooth root apex without evident damage and no root fracture, as determined by x-ray.
2. The patient has three or four walls of intact tooth tissue after root canal treatment
3. The patient has good oral hygiene.
4. The patient has signed an informed consent form.
5. The patient is not participating in any other clinical trial.
6. The patient has received a class A assessment according to FDI criteria for marginal adaptation after restoration.

Exclusion Criteria:

1. Obvious destruction of the apical tissue or presence of large cysts or both
2. Severe periodontitis
3. Oral malignant tumor(s)
4. Undergoing radiotherapy
5. Pregnancy
6. Mental illness or systemic diseases
7. Incapable of self-care
8. Unsuitable for the trial as deemed by the researchers