Additive vs Subtractive Manufacturing for Endocrown Fabrication: A 24-Month RCT

Additive Versus Subtractive Manufacturing for Endocrown Fabrication: A Clinical Comparison of 3D-Printed Ceramic-Filled Photopolymer Resin and CAD/CAM Milled Resin Nano-Ceramics Endocrowns in Posterior Teeth - A 24-Month Randomized Controlled Trial

This randomized controlled trial (RCT) compares the 24-month clinical performance of endocrown restorations fabricated by two digital manufacturing pathways: additive manufacturing using 3D-printed ceramic-filled photopolymer resin (VarseoSmile TriniQ, BEGO) versus subtractive computer-aided design/computer-aided manufacturing (CAD/CAM) milling from hybrid nano-ceramic blocks (HC Hard Block, Shofu). Sixty endocrowns will be placed in endodontically treated posterior molars and evaluated using modified United States Public Health Service (USPHS) criteria at 6, 12, and 24 months. The trial is conducted at the Conservative Dentistry Department, Faculty of Dentistry, Cairo University.

Post-endodontic rehabilitation of extensively damaged posterior molars using endocrowns represents a minimally invasive alternative to conventional crown-plus-post-and-core approaches. Digital fabrication has advanced both the precision and reproducibility of endocrown manufacture. While computer-aided design/computer-aided manufacturing (CAD/CAM) milled hybrid ceramic endocrowns are well-validated clinically, prospective clinical data comparing 3D-printed definitive restorations to milled counterparts are absent. This trial employs a parallel-group, 1:1 randomized design with triple blinding of participants, outcome assessors, and statistician. All restorations are delivered using Beautilink SA self-adhesive dual-cure resin cement. The primary outcome is fracture resistance at 24 months; secondary outcomes include retention, marginal adaptation, marginal discoloration, surface texture, anatomic form, color match, secondary caries, fabrication time, and patient satisfaction assessed by Visual Analogue Scale (VAS).

Inclusion Criteria:

• Age 25-45 years, male or female
• Endodontically treated molar tooth with radiographically confirmed treatment success and no clinical signs of failure
• Sufficient remaining coronal structure for endocrown preparation: minimum three walls, wall thickness 1.5 mm or greater, pulp chamber depth 3 mm or greater, supragingival preparation margins
• Completely erupted tooth with intact periodontal support
• Minimum of 20 occluding teeth
• Satisfactory oral hygiene status
• Capable of providing written informed consent and committed to scheduled follow-up visits

Exclusion Criteria:

• Diagnosed parafunctional habit or nocturnal bruxism
• Uncontrolled systemic illness or physical disability precluding safe participation
• Heavy tobacco use
• Current or suspected pregnancy
• Periapical disease or radiographic signs of endodontic failure
• Evidence of pathological tooth wear or occlusal erosion
• Moderate-to-severe periodontitis or tooth with hopeless prognosis
• Radiographic or clinical evidence of vertical root fracture
• Impaired decision-making capacity or anticipated non-compliance