Aim: To investigate the influence of Contracted Access Cavity (CEC) design and two dissimilar final preparation tapers-using ProtaperNext (PTN) and OneShape (OS) on the canals shaping geometry as compared to the Traditional Access Cavity (TEC) using CBCT. Methodology: Sixty mandibular molars with two separate roots were randomly classified into 4 groups (n=15) were scanned with CBCT, namely: TEC/PTN, TEC/OS, CEC/PTN, and CEC/OS. Instrumentations in each group were done following the manufacturer protocol for each instrument type. A second scan was made after canals instrumentations. Three root levels were selected namely 3,6,and 9mm from the roots apices. Results were statistically analyzed using repeated measure ANOVA followed by paired sample t-test and One-way ANOVA followed by Tukey post hoc test.
Results: all test groups showed significant canals transportation to varying degrees (p<0.05). At 3mm from the apex, TEC/ PT showed statistically significant least transportation, while largest transportation was found in CEC/PT while CEC/OS and TEC/OS values were in between. Comparing the values of transportation using either PTN or OS showed a statistically significant higher transportation values for (CEC) as compared to (TEC) irrespective of the rotary instrumentation used; where (p<0.001). On the other hand for the centering ability, no statistically significant difference between (CEC) and (TEC) groups where found (p=0.060).
Conclusion: Significantly higher transportation values was found for (CEC) as compared to (TEC) irrespective of the rotary instrumentation used. For the centering ability, no statistically significant difference between (CEC) and (TEC) groups where found using either PTN or OS.