This randomized clinical trial aims to evaluate the clinical performance of a 3D-printed hybrid resin (VarseoSmile TriniQ) used for indirect restorations in endodontically treated teeth, compared with a CAD/CAM composite block (Cerasmart). In addition, two different luting protocols will be compared: a preheated microhybrid composite (Enamel Plus HRi) and a resin cement (RelyX Universal).

Sixty patients requiring restoration of an endodontically treated molar with an indirect adhesive overlay will be recruited at the University Dental Clinic of the Universitat Internacional de Catalunya (Barcelona, Spain). Participants will be randomly assigned to receive restorations fabricated either using the printed hybrid resin or the CAD/CAM composite material. Each material group will be further divided according to the cementation technique used.

All restorations will be fabricated following a digital workflow that includes intraoral scanning, CAD design, and either additive manufacturing (3D printing) or subtractive milling. Adhesive luting procedures will be performed according to standardized clinical protocols.

Clinical evaluations will be performed at baseline, 3 months, 6 months, and 12 months, and annually thereafter. The clinical performance of the restorations will be assessed using modified United States Public Health Service (USPHS) criteria, including parameters such as marginal adaptation, contact points, color stability, wear, fracture occurrence, secondary caries, and patient comfort.

The results of this study will provide clinical evidence regarding the behavior of 3D-printed hybrid resin restorations and their potential use as an alternative to conventional CAD/CAM composite materials for indirect restorations in endodontically treated teeth.

Digital dentistry has significantly evolved over recent decades with the development of computer-aided design and computer-aided manufacturing (CAD/CAM) technologies. These digital workflows allow the design and fabrication of indirect restorations with high precision and efficiency. Traditionally, most CAD/CAM restorations have been produced using subtractive manufacturing techniques such as milling. However, additive manufacturing through three-dimensional printing is increasingly being introduced in dentistry and may offer advantages such as reduced material waste, lower manufacturing costs, and the ability to fabricate complex geometries.

Recently, a hybrid ceramic-filled resin specifically designed for additive manufacturing of definitive restorations has been introduced (VarseoSmile TriniQ, BEGO, Bremen, Germany). This material consists of a resin matrix filled with ceramic particles and is indicated for permanent restorations including crowns, inlays, onlays, and veneers. Although promising, clinical evidence regarding the performance of this printed hybrid material is still limited.

Composite CAD/CAM blocks such as Cerasmart (GC, Tokyo, Japan) are widely used for indirect restorations due to their favorable mechanical properties, wear resistance, and reparability. These materials combine characteristics of ceramics and composites and have demonstrated good clinical performance in previous studies. However, it remains unclear whether the newer printed hybrid materials provide comparable clinical outcomes.

Another important factor influencing the longevity of indirect restorations is the luting procedure. Preheated restorative composite resins have been proposed as an alternative to traditional resin cements for adhesive luting of indirect restorations. This technique may improve mechanical properties and reduce marginal gaps, but clinical evidence comparing these approaches remains limited.

The aim of this randomized clinical trial is therefore to evaluate the clinical behavior of indirect overlay restorations fabricated with a 3D-printed hybrid resin (VarseoSmile TriniQ) compared with restorations fabricated from a CAD/CAM composite block (Cerasmart). Additionally, two cementation strategies will be evaluated: a preheated microhybrid composite resin (Enamel Plus HRi) and a resin cement (RelyX Universal).

A total of 60 patients requiring restoration of an endodontically treated molar with an indirect overlay will be recruited at the University Dental Clinic of the Universitat Internacional de Catalunya (Barcelona, Spain). Participants will be randomly allocated into four groups according to the restorative material and cementation protocol used.

All teeth will receive standardized preparation procedures for adhesive indirect overlays, including immediate dentin sealing when indicated. Restorations will be designed using CAD software and fabricated either by additive manufacturing (3D printing) or subtractive milling. Adhesive luting will be performed following standardized protocols using rubber dam isolation.

Clinical evaluations will be performed at baseline, 3 months, 6 months, and 12 months, and annually thereafter. Outcomes will be assessed using modified United States Public Health Service (USPHS) criteria. The evaluated parameters will include marginal adaptation, contact points, color stability, polishability, wear, fracture occurrence, secondary caries, and patient comfort.

The results of this study are expected to provide new clinical evidence regarding the performance of 3D-printed hybrid resin restorations and the influence of different luting protocols in indirect restorations of endodontically treated teeth.

Inclusion Criteria:

• Age ≥18 years
• Signed informed consent
• Need to restore an endodontically treated molar with an indirect adhesive overlay
• Physically and psychologically able to tolerate conventional restorative procedures
• No high caries risk
• No active periodontal disease
• Natural antagonist tooth present
• Need for full cuspal coverage restoration (overlay)
• Remaining wall thickness <3 mm in the endodontically treated tooth
• Occlusal thickness of the restoration ≥1 mm
• Willing and able to attend follow-up visits

Exclusion Criteria:

• Poor oral hygiene
• Uncontrolled parafunctional habits (e.g., bruxism)
• High caries risk
• Active periodontal disease
• Active pulpal disease
• Absence of natural antagonist tooth
• Need for partial cuspal coverage restoration (inlay or onlay)
• Insufficient interarch space for restoration
• Teeth planned as abutments for removable or fixed prostheses
• Known allergy to any materials used in the study

Individual participant data will not be made publicly available due to institutional data protection policies and patient confidentiality considerations.

The clinical evaluator responsible for assessing the outcomes will be blinded to the restorative material and luting protocol used. Due to the nature of the interventions, operators performing the procedures cannot be blinded.