Aim: to compare the shaping ability of two rotary systems (Protaper Universal and
Protaper Next) and K-file hand instruments in curved root canals of extracted human
molars.
Materials and methods:Thirty extracted molars with curved canals were cho
sen. The
curvature of root canals was determined (15-40o) then the sample was randomly divided
into three groups: n1=n2=n3=10. Group(1): was prepared using K-file hand instruments
(Stand), group(2): prepared by Protaper Universal (PTU), whereas group3: prepared by
Protaper Next (PTN).The curvature after preparation and Time preparationwere evaluated.
Data were collected and statistical analysis was conducted.
Results: The three instrument systems (PTU, PTN, Stand) have caused significant
change in original canal curvature(P<0.05). On the other hand, there were no significant
differences between systemsin straightening of canal curvature (P>0.05). However, both
systems: PTN, Stand were significantly faster than PTU during preparation of curved
canals (P<0,001).Conclusion: under the conditions of this study, it can be concluded
thatall instruments caused changing in original canal curvature. However, the new
generation PTN was faster than old one PTU.