Aim of the study was to investigate the effect of taper and sealer materials on the fracture resistance (FR) of roots.

Material and method: Total number of 120 single-canalled human mandibular central and lateral teeth with equal size were chosen and kept in distilled water until needed, all teeth were decoronated and divided into one positive control group (n=12) and three experimental groups (n=36) according to the degree of taper used for root canal instrumentation using K3XF files system (#25/4%, #25/6% and #25/8%), each experimental group was further subdivided into one negative control subgroup (n=12) in which the root canal instrumented but not obturated and two experimental subgroups (n=12) according to type of root canal sealer used for obturation (AH Plus and MTA Fillapex ). Each specimen was embedded in acrylic mould and subjected to FR test using a universal testing machine. The force required to fracture each specimen was recorded and the data obtained were statistically analysed.

Results: Group 1 showed highest FR among all experimental groups followed by group 2 with non-significance difference between both groups while group 3 (#25/8%) showed the least FR. MTA Fillapex subgroup showed less non-significantly difference from AH Plus subgroup regardless the degree of taper used for preparation.

Conclusion: Using 4% and 6% taper preparation have non-significant difference from each other when using AH plus or MTA Fillapex sealer. MTA Fillapex did not significantly improve the FR of the root regardless the preparation taper used.