Clinical Comparison of Lithium Disilicate and 3D-Printed Resin Endocrowns

Restoration of endodontically treated posterior teeth presents significant clinical challenges due to the loss of tooth structure and increased susceptibility to fracture. Indirect adhesive restorations, particularly endocrowns, have emerged as conservative treatment alternatives that aim to preserve the remaining tooth structure while providing adequate mechanical resistance and functional stability.

Lithium disilicate ceramics, such as IPS e.max CAD (Ivoclar), are widely used for indirect restorations due to their favorable mechanical properties, esthetic characteristics, and documented clinical performance. In contrast, three-dimensional (3D) printing technologies have introduced resin-based materials, such as BEGO VarseoSmile TriniQ, as alternative restorative options. These materials offer potential advantages related to manufacturing efficiency and mechanical behavior. However, comparative clinical evidence regarding the performance of 3D-printed resin and lithium disilicate endocrowns remains limited.

The primary objective of this randomized controlled clinical trial is to compare the clinical performance of CAD/CAM lithium disilicate and 3D-printed resin endocrown restorations in endodontically treated posterior teeth over a 12-month follow-up period. The study also aims to evaluate restoration survival and potential biological, functional, and esthetic complications.

This study is a prospective, randomized, controlled clinical trial with two parallel treatment groups, conducted at the Department of Endodontics, Faculty of Dentistry, Istanbul Medipol University, Türkiye.

A total of 60 patients were enrolled and allocated to two treatment groups, with 30 patients in each group.

• **Group 1 (n = 30):** Endocrown restorations fabricated from lithium disilicate ceramic blocks using CAD/CAM technology (IPS e.max CAD, Ivoclar).
• **Group 2 (n = 30):** Endocrown restorations fabricated from 3D-printed permanent resin material (VarseoSmile TriniQ, BEGO).

Patients aged 18-65 years with an American Society of Anesthesiologists (ASA) physical status classification of I or II and requiring indirect endocrown restoration of endodontically treated posterior teeth were eligible for inclusion. Eligible teeth were required to have clinically and radiographically acceptable root canal treatments, adequate remaining tooth structure, stable occlusal conditions, and the possibility of rubber dam isolation.

Patients with uncontrolled systemic diseases, untreated periodontal disease, parafunctional habits, inadequate oral hygiene, or conditions potentially affecting restorative outcomes were excluded.

All restorative procedures were performed by a single experienced clinician following standardized clinical protocols.

Following clinical and radiographic examination, the teeth were prepared according to the principles of adhesive indirect restorations. Functional cusps were reduced by approximately 2 mm and nonfunctional cusps by 1.5 mm, depending on the remaining tooth structure. Deep margin elevation and undercut management were performed when necessary.

Digital impressions were obtained using an intraoral scanner (TRIOS 3, 3Shape). The restorations were designed using a standardized digital workflow, with the cement space set to 100 μm.

Lithium disilicate restorations were manufactured using CAD/CAM technology, whereas resin restorations were fabricated using 3D printing technology.

Before adhesive cementation, the intaglio surfaces of lithium disilicate restorations were conditioned using hydrofluoric acid etching followed by silane application. The intaglio surfaces of 3D-printed resin restorations were treated by airborne-particle abrasion and subsequent surface conditioning according to the restorative protocol.

All restorations were adhesively cemented under rubber dam isolation using a resin-based luting system. Occlusal adjustments and polishing procedures were performed following cementation.

Patients are being evaluated at one week, six months, and 12 months following restoration placement.

The clinical performance of the restorations is assessed according to the World Dental Federation (FDI) criteria, including functional, esthetic, and biological properties.

The following clinical parameters are evaluated:

• Functional properties, including fracture resistance, retention, marginal adaptation, and occlusal performance.
• Esthetic properties, including surface characteristics, color matching, and staining.
• Biological properties, including secondary caries, periodontal response, and tooth integrity.
• Restoration survival and complications, including fracture, debonding, and the need for repair or replacement.

Periapical radiographs are obtained at six and 12 months to evaluate periapical changes and endodontic outcomes. Radiographic evaluations are independently performed by investigators.

Data obtained from the two treatment groups will be analyzed using appropriate statistical methods to compare clinical outcomes and restoration performance. Descriptive statistics will be used to summarize patient characteristics and clinical findings. Between-group comparisons will be performed according to the distribution and characteristics of the collected data.

The statistical significance level will be set at p \< 0.05.

This study aims to provide comparative clinical evidence regarding the 12-month performance of CAD/CAM lithium disilicate and 3D-printed resin endocrown restorations in endodontically treated posterior teeth.

The findings may contribute to evidence-based clinical decision-making and material selection for indirect restorations, particularly regarding the potential clinical applicability of 3D-printed permanent resin materials as alternatives to conventional lithium disilicate ceramics.