eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2018-06-25 11 2 751 757 10.13005/bpj/1429 20381 article Zahraa Abdulaali Jlekh 1 Zainab M. Abdul-Ameer 1 Department of Conservative and Cosmetic Dentistry, College of Dentistry, University of Baghdad, Baghdad, Iraq. This in vitro study aimed to assess and compare premolars cuspal deflection that restored with different bulk fill resin materials types (SonicFill^TM2, Beautifil Bulk Fill restorative, and Filtek^TM Bulk Fill posterior restorative) to those incrementally restored group with conventional composite restorations (low shrinkage universal Tetric Evoceram). A total of 40 intact human maxillary first premolars were prepared into large MOD. Then teeth were randomly classified into four groups (n=10 for each group) according to restorative materials as following: Group A: Teeth were restored with Sonic Fill^TM2 composite, Group B: restored with Beautifil Bulk Fill restorative material, Group C: Teeth were restored with Filtek Bulk^TM Fill posterior restorative, and Group D: Teeth were restored with Universal Tetric Evo Ceram®. Digital microscope was used to measure intercuspal distance between two index reference points on the tips of the cusps before preparation, after preparation, and 15minutes after completion of restorations. The differences registered as cuspal deflection. All teeth were exposed to inward cuspal deflection after restoration and all groups that restored with bulk fill restoration reported lower cuspal deflection in compared to group D that restored with conventional composite in layering technique. Beautifil Bulk Fill restorative produced significantly greater cuspal deflection than other bulk fill groups. The study concluded that the use of new bulk fill restorative materials might reduce amount of cuspal deflection significantly. However, type of bulk fill restorative materials also influenced on amount of cuspal deflection so restoration with Sonic Fill™2 composite and Filtek Bulk™ Fill posterior reported lower cuspal deflection than Beautifil Bulk Fill restorative material. https://biomedpharmajournal.org/vol11no2/evaluation-of-the-cuspal-deflection-of-premolars-restored-with-different-types-of-bulk-fill-composite-restoration/ Beautifil Bulk Fill Restorative Material  Bulk Fill Cuspal Deflection  Filtek Bulk^TM Fill Posterior Restorative    Intercuspal Distance Sonic Fill^TM2 Composite