This study is conducted to evaluate the clinical performance of two fiber-reinforced resin composite restorations compared to nanohybrid resin composite restorations in patients with posterior MOD cavities

Statement of the problem:

With limited evidence based information in literature about using fiber-reinforced composite (FRC) restorations in stress bearing posterior areas, it is beneficial to evaluate the newly introduced materials using a randomized clinical trial to test the null hypothesis that this new material "fiber reinforced resin composites" will have the same clinical performance as the nanohybrid resin composite restoration in such situation

Rationale:

Improvements concerning the esthetic and mechanical properties of dental resin composites have resulted in widespread use of these materials in both anterior and posterior teeth. However, resin composites still have a number of limitations in posterior teeth, mainly because of problems related to technique sensitivity, polymerization shrinkage and low fracture resistance, Due the failures of this kind, it is still controversial, whether restorative composites should be used in large high-stress bearing applications such as in direct posterior restorations.

Fiber-reinforcement of resin-based composite restorations has been proposed to increase resistance of materials fracturing under high stress-bearing cavities. Fiber-reinforced composite (FRC) is made of a polymer matrix, impregnated with fibers. The fibers allow the stresses to be distributed throughout the restoration. Since the role of the fibers is to improve the structura lproperties of the material by acting as crack stoppers, the FRC framework provides strength and rigidity of the composite materials.

The common types of fibers used in dentistry are glass and polyethylene fibers. Composite resin reinforced with short E-glass fiber fillers showed substantial improvements in the load bearing capacity, the flexural strength and fracture toughness of in comparison with conventional particulate filler restorative composite resin. The short fiber composite resin has also revealed control of the polymerization shrinkage stress by fiber orientation and, thus, marginal microleakage was reduced compared with conventional particulate filler restorative composite resins.

Polyethylene fibers are one of the most durable reinforcing fibers available. They are made of aligned polymer chains, having low modulus and density, and presents good impact resistance.They are white in colour and thus it is possible to use them in aesthetic dental applications, the use of polyethylene fiber ribbon in combination with bonding agent and flowable composite under composite restoration may act as a stress absorber because of its lower elastic modulus thereby increasing fracture resistance

Inclusion Criteria:

• MOD carious lesions premolars and molars.
• Vital upper or lower teeth with no signs of irreversible pulpitis.
• Presence of favorable occlusion and teeth are in normal contact with the adjacent teeth.

Exclusion Criteria:

• Deep carious defects (close to pulp, less than 1 mm distance).
• Periapical pathology or signs of pulpal pathology.
• Endodontically treated teeth.
• Tooth hypersensitivity.
• Possible prosthodontic restoration of teeth.
• Heavy occlusion and occlusal contacts or history of bruxism
• Severe periodontal affection.