Objectives. To investigate the effect of different bulk filling techniques of resin composite on the development of polymerization stresses at the interface reflected as cuspal deflection and strain developed upon loading within teeth restored by different bulk filling techniques and to measure the effect of such techniques on the curing depth of resin composite.Methods. A standardized MOD cavity was prepared in thirty extracted maxillary premolars of almost similar size. They were divided into three main groups, group A: restored by conventional consistency composite in incremental technique (control group), group B: the cavity was lined with the SDR (flowable bulk filling composite) up to 4mm covered by 2mm of the conventional composite and group C: restored by conventional consistency composite filled in bulk.Cuspal deflections were recorded by measuring the distance between fixed points on the cusps using a universal measuring microscope. Teeth were then thermocycled and subjected to a load of 100 N and strain upon loading was recorded using a strain meter. The curing depth test was conducted according to ISO Standard 4049 by measurement of the specimens length of resin composite cured in Teflon moulds using a digital caliper.Results The bulk filling technique using SDR significantly reduced cuspal deflection .The strain developed by using SDR was lowered although there was no significant differences between the three groups. The bulk filling technique using SDR and the incremental filling techniques led to a significantly higher depth of cure than conventional bulk filling.Significance : Bulk filling techniques using the new flowable bulk filling composites may be a proper technique for reduction of cuspal deflection. As well as minimizing the strain during loading.