Method:
Sixty single-rooted exracted mandibular premolars were decoronated to a length of 13 mm and then were randomly divided into 2 main groups (n=30 in each group) according to the rotary system used for preparation. First group were instrumented by using the ProTaper System up to a master apical file size of F2 while second group enlarged with OneShape System. Two main group were then divided into 3 subgroups according to the sealer used (n=10) and filled with gutta percha (either F2 or MM-GP Points) of the rotary system used and one of the sealer: Group 1, BioRoot RCS (Septodont, France)+ProTaper F2 gutta-percha; Group 2, AH Plus (Dentsply, Germany)+ProTaper F2 gutta-percha; Group 3, GuttaFlow (Coltene, Germany)+ ProTaper F2 gutta percha, Group 4, BioRoot RCS+ MM-GP Points; Group 5, AH Plus+MM-GP Points; Group 6, GuttaFlow+MM-GP Points. All groups were obturated using matched-taper single cone technique and stored for 1 week at 100% humidity to allow the complete sealer setting. Each specimen was then subjected to fracture testing by using a universal testing machine at a crosshead speed of 1.0 mm/min until the root fractured. Data were statistically analyzed by using Two-way Anova.
Result:
Two-way Anova test showed not significant differences among the all groups (p=0.051). OneShape instruments showed significantly better fracture resistance when compared ProTaper instruments (p=0.002). Statistically, no significant difference was found between BioRoot RCS, AH Plus and GuttaFlow sealers (p=0.782).
Conclusion: It can be concluded that rotary system used for the instrumentation of teeth has some influence on the fracture resistance while root canal sealers have not.