clinical performance of short fiber reinforced resin composite versus indirect nanohybrid resin composite onlay restorations in complex proximal cavities of molar teeth will be evaluated over one year.

Resin composite materials have been rapidly developed in the latest few years. Direct resin composite restorations become the golden standard for restoring intracoronal cavities. While for the extracoronal cavities, the indirect resin composite onlays tend to replace metallic restorations in most situations being more esthetic and conservative with lower cost (Rocca & Krejci, 2007).

Indirect resin composite onlays usually are lab processed in two appointments but it can be made in one appointment through CAD/CAM technology or by flexible model technique (semidirect technique).

These restorations offer more control on the proximal contacts and the anatomic form over the direct approach. Polymerization shrinkage occurs outside the patient mouth so the stresses are decreased and become limited to the width of the luting space. Annual failure rate (AFR) of indirect posterior resin composite restorations is up to 10% (Manhart et al, 2004).

One of the advancement in resin composite technology is the evolution of short fiber reinforced resin composite (SFRC) material that allows making a direct onlay restoration possible thus offers less procedural steps and saves more time (Garoushi et al, 2013).

This material is made to be used as a dentine substitute in the high stress-bearing areas. It is covered by a conventional resin composite filling to act as the enamel replacement this combination gives us a kind of biomimetic restoration.

Inclusion Criteria

1. Pulp asymptomatic vital carious upper or lower molars.
2. Proximal complex carious cavities involving one or two weak cusps.
3. Replacement of old amalgam or resin composite restoration due to recurrent caries or either tooth or restoration fracture.
4. Presence of favorable occlusion.
5. Healthy volunteers

Exclusion Criteria:

1. Teeth with signs and symptoms of irreversible pulpitis or pulp necrosis.
2. Deep subgingival cavity margins.
3. Possible future prosthodontic restoration of teeth.
4. Severe periodontal problems.
5. Medically compromised patients.

The outcome assessors will be blinded to the material type