The bond strength of Total fill BC obturation system using single cone size 40 and size 50 at different time intervals; 1days and 7 days was evaluated in this vitro study. Twenty four single rooted single canal extracted human teeth were used in this study. All the teeth were instrumented with a crown down technique by Endo Star taper 4% to achieve size #50 apical preparation .irrigation was done using 10ml 2.25% Na(ocl), then 10ml of 17% EDTA and final rinse with 10ml sterile normal saline. Single cone technique was used for obturating all the groups as the manufacturer's instructions .The samples were classified into two main groups according to the size of the obturating material (n=12); group “I" canals were obturated with Totalfill points size 50 and group “II" (canals were obturated with Totalfill points size 40. Each group was subdivided into 2 subgroups according to the time of the test (n=6); subgroup “1' examined after 1 day and Subgroup “2" examined after 7 days. Each subgroup is tested using universal testing machine to evaluate the push out Bond strength.
after 1 day; there was no statistically significant difference between the two groups, However After 7 days regardless of root level, the Group obturated with size 50 showed statistically significantly higher median push-out bond strength than Group obturated with size 40.it was concluded that The bond strength is higher with the large size of gutta percha core than the volume of sealer.