Evaluation of Wear Resistance of CAD/CAM Hybrid Ceramic and Nano-Hybrid Composite Overlays in Endodontically Treated Molars and Their Effect on Natural Antagonist Teeth

The rationale for this 24-month RCT is driven by the need for high-level, evidence-based data to guide clinical material selection for compromised teeth. This trial is designed to directly compare two materials specifically engineered to be stress-absorbing in the oral environment. The primary intervention, the SHOFU Restorative System (Hard blocks), is a Hybrid Ceramic engineered to combine the durability of ceramics with the elasticity of polymers. Its reduced hardness and dentin-like modulus allow for rapid machining and are associated with reduced antagonist abrasion compared to conventional ceramics. The second material, serving as the comparator, is the Coltène Restorative System (BRILLIANT Crios), which is a reinforced nano-hybrid composite characterized by an elastic modulus comparable to dentin, designed for optimal shock absorption and confirmed to be gentle on antagonist teeth.

Focusing the study on endodontically treated molars addresses a highly prevalent clinical scenario where maximizing the longevity of the restoration and the remaining tooth structure is paramount. The use of a full-cusp-coverage overlay design represents the maximum conservation approach for these compromised teeth while ensuring that the selected restorative materials do not exert harmful effects on opposing dentition.

Inclusion criteria

• Age between 22 and 45 years.
• Low to moderate caries risk.
• Normal occlusion.
• Absence of signs or symptoms of temporomandibular joint (TMJ) disorders.
• Satisfactory oral hygiene.
• Medically fit to receive routine restorative dental treatment.
• Permanent molars.
• Asymptomatic endodontically treated teeth.
• Homogeneous root canal fillings extending 1-2 mm from the radiographic apex.
• Compound cavities.
• Favorable occlusion.
• Presence of both an adjacent tooth and a sound opposing tooth in occlusion

Exclusion criteria

• * Presence of bruxism.

• Poor patient cooperation.
• Inability or unwillingness to attend follow-up appointments.
• Anticipated travel during the study period.
• Poor oral hygiene.
• Chronic or advanced periodontitis.
• Known allergies to any of the materials used in the study.
• Patients who are pregnant or breastfeeding.
• Teeth with <1" mm" of residual wall thickness.
• Deep subgingival cavity margins.
• Severe periodontal problems.
• Radiographic signs of apical pathology.