Aim: The aim of this in vitro study is to evaluate the fracture resistance of endodontically treated teeth restored with different restorative materials.

Materials and Methods: Fifty single rooted non-carious, non-restored, intact human premolars extracted for orthodontic purposes were considered. Access cavities were prepared and biomechanical preparations were done followed by obturation. Class II (MOD) cavities were prepared using a straight fissure bur and restored with different restorative materials. Samples were randomly divided in to 5 groups (n=10). Fracture resistance evaluated using a Universal Testing Machine (UTM) at a cross head speed of 1mm/min and the force required to fracture each tooth was recorded in newtons (N).

Results: There is a statistically significant difference in the mean values of the study parameter between the groups. Highest mean values were observed with Ribbond+ Packable+ Flowable followed by Ribbond +Packable.

Conclusion: Use of polyethylene ribbon fiber beneath the composite restorations considerably increased the fracture strength. Use of flowable composite beneath the packable restoration increased the fracture resistance.