Advances in digital dentistry coupled with increased demand for aesthetic restorations have led to developments in CAD CAM( Computer Aided Design and Computer Aided manufacturing)systems for manufacturing tooth restorations. CAD CAM restorations have the added benefit of digital impressions which eliminate the need to take conventional impressions, something patients find difficult to tolerate. CAD CAM restorations are now part of routine dental care. However there are no clinical studies evaluating these restorations on root canal treated teeth

This study aims to compare the success and survival of root canal treated teeth and/or restoration with varying degrees of tooth structure loss restored using CAD CAM restorations.

Null Hypothesis:- The amount of residual coronal dentin has no effect on the survival of root canal treated teeth and/or restoration.

This study will be carried out at KCL Dental Institute at Guy's Hospital and will form part of the routine dental treatment done at the endodontic postgraduate unit. Potential volunteers will be given written information about the process and be given time to consider participation. Once any questions have been answered, fully informed written consent will be obtained if they are interested in taking part. Patients requiring endodontic treatment with varying degrees of tooth structure loss will be detected, diagnosed and treated by endodontic MClinDent postgraduate students at Guy's hospital using suitable clinical techniques. The teeth will then be restored using CAD CAM restorations. Dental periapical radiograph and cone beam computed tomography (CBCT)scans (Morita Accuitomo) will be taken at baseline, 12 months and 24 months. Clinical assessment and radiographical evaluation will be carried out immediately after endodontic treatments have been accomplished and 1 and 2 years post treatment and will be assessed independently by a group of examiners. It is hoped that data analysed from this study will provide a definitive clinical evidence base for the success and survival of endodontically teeth and/or restorations.

Inclusion Criteria:

1. Patients either male or female over the age of 18 (who can consent for themselves) in good general health.
2. The selected teeth needed to be in occlusal function with a natural tooth and in interproximal contact with two adjacent natural teeth.
3. Molar or premolar teeth with suspected endodontic problems that require root canal treatment.
4. Teeth should not be mobile and must be restorable.

Exclusion Criteria:

1. Pregnant women, in view of requirements for radiographs (or if they could possibly be pregnant). To be confirmed by the Medical History Questionnaire.
2. Patients younger than 18.
3. Patients unable to give consent.
4. Teeth with probing periodontal depths greater than 5 mm.
5. Non-restorable teeth.
6. Not involving patients from prisons.
7. Not involving patients who cannot read, write or understand English

Routine patients requiring root canal treatment at Guy's Hospital, London

De-identified individual data for all primary and secondary outcome measurements will be made available

Data will be available within 6 months of study completion

Data access requests will be reviewed by an external independent review panel. Requestors will be required to sign a Data Access Agreement