Class II cavities ( 7 mm occluso-gingival height , 2 mm mesio-distal depth of the box , 4 mm occlusal depth , 4 mm bucco-lingual width ) were prepared in 50 molars and randomly divided into five groups ( n = 10 ) , according to the material : SureFil SDR flow ( SDR ) , Filtek Silorane ( FS ) and experimental materials ( G-aenial Flo bulk fill , GF ; G-aenial Universal Flo bulk fill , GUF ; GC Kalore bulk fill , GK ) .