Purpose: to assess the morphologic changes of the C-shaped canal system before and after instrumentation using a NiTi rotary system or traditional stainless steel instruments
N= 24 mandibular molars with C-shaped canals. (selected according to the type of pulp floor, 3D configuration, and number of main canals and apical foramina)
Inclusion criteria: teeth with completed root formation without visible apical resorption.
•The teeth with C shaped canals were selected in pairs and sorted equally into 2 groups. (n=12/Group).
•The 1st group was instrumented with a crown-down approach using the ProTaper rotary instruments and the 2nd group was instrumented with the step-down technique by K-files and Gates-Glidden burs.
•Three dimensional images were constructed by micro-CT (pre-instrumentation and post-instrumentation).
•The volume of dentin removed, un-instrumented canal area, time taken for instrumentation, and iatrogenic error of instrumentation were investigated.
Most highlighted Results:
The importance of chemical cleaning of C-shaped canals because of the large percentages of untouched areas after preparation of both types of instruments. To reduce procedural errors and reach larger areas of the walls of c shaped canals, a combination of rotary and hand instruments may be used.
Strengths: matching pairs of C-shaped canals to decrease the confounding variables between the 2 groups.
weakness: all the procedures performed by a single operator.