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

Clinical Performance and Restoration Fit of 3D-Printed Versus Milled Biomimetic Resin Composite Endocrowns: 18-Month Randomized Clinical 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.

Eligible participants will be recruited from the Conservative Dentistry Department, Faculty of Dentistry, October 6 University.

Following confirmation of satisfactory root canal treatment. Tooth preparation will follow standardized endocrown guidelines. All preparations will be performed by a single calibrated operator (Y.A.E.).

Full-arch digital impressions will be captured using an intraoral scanner, including scans of the prepared tooth, opposing arch, and bite registration. Digital files (STL format) will be used to design definitive restorations in CAD software. Following digital design, participants will be randomly allocated (1:1 ratio) to one of two fabrication groups:

Group 1 (Intervention): Additive manufacturing (3D-printed resin composite) Group 2 (Comparator): Subtractive manufacturing (milled resin composite) Teeth will be temporized with intermediate restorative material, then temporary materials will be removed and preparations cleaned. Restorations will be tried to verify fit, contacts, and occlusion.

After cementation, scan the seated restoration with the same intraoral scanner to create baseline restoration STL file (T0) for longitudinal fit assessment. Participants will be recalled at baseline (T0), 6 months (T1), 12 months (T2) and18 months (T3). At each visit, restorations will be evaluated using Modified FDI criteria (clinical performance) and 3D digital superimposition (Restoration fit via Geomagic Control X)

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.