This Study is Conducted to Evaluate the Clinical Performance of Indirect Overlay Restorations With Different Cavity Preparation Designs in Endodontically Treated Molars.

First Validation of endodontic treatment using a periapical radiograph and proper history taking.

{I}• Cavity Preparation Procedures for Comparator Group:

• Removal of any remnants of temporary filling and excess gutta percha to the level of root canal orifice.
• Removal of all undermined enamel.
• Then 1.5 to 2 mm cusp reduction will be performed for the buccal and lingual walls.
• The occlusal box will be of 2.5 mm width, 2 mm depth cavity walls and will be flared to produce a 6 degree of divergence.
• The cavity will have internal rounded angles, finished enamel with sharp non-beveled margins and smooth well-defined walls.
• Immediate Dentin Sealing and Cavity Optimization: Immediate dentin sealing will be performed through the use of a universal adhesive followed by the injection of injectable flowable resin composite. Blocking of undercuts using injectable flowable resin composite and margin elevation if required.
• The final retentive design will include occlusal clearance of 2 mm with occlusal box cavity of depth 2 mm with all margins in enamel occlusally and all dentin surfaces will be covered.

{II}• Cavity Preparation Procedures for Intervention Group:

• Removal of any remnants of temporary filling and excess gutta percha to the level of root canal orifice.
• No additional removal of the tooth structure will be performed at this step.
• Cavity optimization will be performed first.
• Blocking of undercuts using injectable flowable resin composite and margin elevation if required.
• The occlusal cavity will be restored during cavity optimization with injectable resin composite to reduce the areas of dentin exposure and preserve the remaining tooth structure.
• The dentin substitute resin composite will establish the biobase.
• An anatomical non retentive preparation design will be performed to show continuous inclined plane preparation with 2 mm cuspal reduction, concave chamfer margins, and 1 to 1.5 mm thick butt-joint preparation in the interproximal portion.
• The final cavity design will include occlusal clearance of 2 mm with total cusp coverage, with biomimetic features (anatomical, non-retentive design) with no occlusal box cavity.

• The CAD/CAM partial coverage overlay restoration will be designed, then milled using SHOFU Hard hybrid ceramic blocks for both groups following its design.
• Cementation for both groups:
• Selective etching of the enamel margins of the cavity will be made using 37% phosphoric acid.
• Application of Universal Adhesive according to manufacturer's instructions and cured.
• Regarding the milled indirect overlay restorations; surface roughening with Dura-Green Stones SHOFU will be performed, followed by the application of a suitable priming agent, then the injection of resin cement in the fitting surface, and finally the restoration will be cemented.
• Restoration will be placed onto the prepared cavities allowing for excess resin cement to emerge which will then be tac-cured for 5 second using a standard intensity light cure allowing for slight hardening of the excess resin cement.
• Removal of excess cement using a sharp explorer, excavator or a c-blade along with the use of interdental flossing to ensure elimination of interdental excess resin cement material.
• Completing the remaining curing cycle after excess removal to the full curing time.

Inclusion criteria

Patient Related Criteria:

• Adult patients (age: 20-60 years) of both genders.
• Healthy patients (not suffering of any systematic or chronic diseases).
• Able to tolerate the necessary restorative procedures.
• Willing to sign the informed ethical consent.
• Accepts the follow-up period.

Tooth Related Criteria:

• Proper endodontically treated teeth.
• First and second permanent molars.
• Absence of any peri-apical lesions.
• Absence of any periodontal disease involvement.
• Large access cavities with one or two missing walls.
• Patients with proper oral hygiene.
• Presence of opposing tooth.

Exclusion criteria

• Patient related:
• Patients younger than 20 or older than 60 years old.
• Pregnant females.
• Patients with any systemic or chronic diseases.
• Patients not accepting the follow-up period.
• Patients not willing to sign the informed ethical consent.
• Patients with known allergies to latex and/or resinous material.

Tooth related

• Endodontically treated anterior, premolar and third molar teeth.
• Hopelessly carious/destructed teeth necessitating extraction.
• Mobile teeth, indicating periodontal disease or trauma.
• External or internal resorption.
• Poor endodontic treatment.
• Periapical lesion present.
• Cervical carious lesions involved.