Clinical Performance and Fit of 3D-Printed Versus Milled Endocrowns: An 18-Month Trial

The goal of this clinical trial is to learn whether 3D-printed resin composite endocrowns perform as well as milled resin composite endocrowns in restoring endodontically treated teeth. It will also learn how well the restorations fit over time. The main questions it aims to answer are: Do 3D-printed endocrowns and milled endocrowns show different clinical performance? Do 3D-printed endocrowns and milled endocrowns differ in restoration fit over 18 months? Researchers will compare two fabrication methods: Additive manufacturing: 3D-printed resin composite endocrowns. Subtractive manufacturing: milled resin composite endocrowns. Participants will: Be recruited from the Conservative Dentistry Department, Faculty of Dentistry, October 6 University. Receive tooth preparation after confirmation of satisfactory root canal treatment. Have their teeth prepared using standardized endocrown guidelines by one calibrated operator. Have digital scans taken of the prepared tooth, opposing arch, and bite registration. Have restorations designed digitally and then assigned randomly to one of the two groups. Receive a temporary restoration until the final endocrown is ready. Have the final restoration tried in for fit, contacts, and occlusion before cementation. Have a baseline post-cementation scan taken for fit assessment. Return for follow-up visits at baseline, 6 months, 12 months, and 18 months. Be evaluated at each visit using Modified FDI criteria and 3D digital superimposition for fit analysis.

Inclusion Criteria: \- Patient-Related Criteria 1. Age: Between 20 and 40 years. 2. Oral Hygiene: Good oral hygiene, evidenced by low plaque and gingival index scores. 3. Willingness to attend regular follow-up visits during the study period \- Tooth-Related Criteria 4. Endodontic Quality: High-quality root canal treatment with no clinical or radiographic signs of pathology. 5. Tooth Type: A permanent molar tooth requiring an endocrown after successful root canal treatment. 6. Located in functional occlusion and opposing natural teeth in stable occlusal contact with the restored tooth. 7. Teeth free from cracks, fractures, or internal resorption; supporting tissues without structural defects that may compromise restoration success Exclusion Criteria: \- Patient-Related Criteria 1. Parafunctional Habits: Severe bruxism, clenching, or other parafunctional habits. 2. Allergies: to any study materials (e.g., resin composites, bonding agents). 3. Patients with systemic diseases contraindicate elective dental treatment (e.g., uncontrolled diabetes) \- Tooth-Related Criteria 4. Insufficient Tooth Structure: Less than 2mm of circumferential sound denting height or deep, unrestorable. 5. Tooth opposes prosthetic restoration. 6. Teeth with a history of fixed prosthetic restorations (previous crowns, inlays/onlays, or bridge restorations) 7. Periodontal Issues: Active periodontal disease, excessive mobility (\> Grade 1, or a hopeless long-term prognosis.