Class II cavities ( @ mm occluso-gingival height , @ mm mesio-distal depth of the box , @ mm occlusal depth , @ mm bucco-lingual width ) were prepared in @ molars and randomly divided into five groups ( n = @ ) , 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 ) .