Clinical performance of direct fiber reinforced resin composite restorations versus direct microhybrid resin composite restorations in endodontically treated molars will be evaluated over 12 months using modified USPHS criteria.

Restoration of endodontically treated teeth is one of the main challenges in restorative dentistry. There are structural changes in endodontically treated tooth: dehydration of dentin, mutation of collagen due to the effect of irrigation and reduction of hardness. This alteration together with loss of tooth structure inflicts a negative impact on long term prognosis of the endodontically treated tooth increases incidence of dental fracture.

Endodontically treated teeth were restored traditionally by crown but this approach is invasive with many technical and clinical steps that prolong the time of treatment. Adhesive philosophy and resin composite were developed and enhanced within the last thirty years that give clinician conservative option also strengthen, protect the tooth against fracture and changed the doctrine of devitalized tooth must be restored by crown. Current studies encourage applying conservative approach and restoring endodontically treated teeth with bonded restorations, so a lot of classic indications of crown in restoring endodontically treated teeth are questioned now.

Microhybrid resin composite restorations permit application of conservative approach that preserves remaining sound tooth structure. Fiber reinforced resin composite improved strength, toughness and fracture resistance of conventional resin composite and restored teeth.

Fiber reinforcement of conventional resin composite is introduced aiming to improve their physical, mechanical properties and tooth fracture resistance. The improvement of the properties was interpreted due to the rule of fibers in stopping crack propagation and transferring stress from matrix to fibers, also it was suggested that fiber Reinforced Resin Composites decrease polymerization shrinkage and shrinkage stress. fiber-reinforced resin composites are used as a dentine substitute combined with conventional resin composites as an enamel replacement.

Inclusion Criteria:

• Patients with Good oral hygiene.
• Co-operative patients approving to participate in the study.
• Endodontically treated molar with minimum to moderate loss of tooth structure.
• Presence of antagonists

Exclusion Criteria:

• Patients with advanced periodontal disease.
• Patients with parafunctional habits.
• Patients with temporomandibular joint disorders.
• Teeth with failed endodontic therapy or extensive caries.
• Pregnant female