A Randomized clinical trial to evaluate the clinical assessment of thermo-viscous versus conventional bulk fill resin composite in proximal compound posterior teeth.The null hypothesis is that there is no difference between thermo-viscous and conventional bulk fill resin composite.

Despite the improvements in resin composite materials some drawbacks still compromise the longevity of resin composite the most frequent reported limitations are related to polymerization shrinkage , to overcome these problem attempts have been made to improve the mechanical properties , the high viscosity and material stickiness as well as adaptation of the material to the walls was difficult and unpredictable .

Preheating is a method that decreases resin composite viscosity results in better adaptation and wettability of the prepared cavity walls reducing the microleakage.

A new approach based on therm-viscous technology Viscalor bulk (VOCO, Cuxhaven ) a high Viscous composite material at room and body temperature by heating to 68 C converted to flowable consistency.

Preheating composite regarding the lab research have significant clinical advantages as better adaptation reduced leakage and increase of mechanical properties .

Follow up Period will be 1 year , Evaluation will be done at baseline , after 6 months and 12 months .

Inclusion Criteria:

• Patients aging more than 18 years .
• Patients with a high level of oral hygiene.
• Patients having at least 12 posterior teeth in occlusion.
• Patients with good likelihood of recall availability.

Tooth Inclusion :

• Permanent premolars and molars.
• Moderate to deep compound class II cavities.
• well formed fully erupted .
• Vital with positive reaction to cold and hot stimulus.

Exclusion Criteria:

• Participants with general systematic illness.
• Pregnant or lactating females.
• Concomitant participation in another research study.
• Inability to comply with study procedures.
• Heavy Bruxism habits.
• Patients receiving Orthodontic treatment.
• last experience with allergic reactions against any component of used materials .

Tooth exclusion :

• Non vital teeth.
• Secondary carious lesions.
• Teeth with clinical symptoms of pulpitis such as spontaneous pain or sensitivity to pressure.