Abstract
Introduction
This study aimed to evaluate the effects of root canal enlargement on the danger zone
(DZ) of mandibular molars.
Methods
Thirty mesial roots of mandibular first molars were scanned in micro-computed tomography
(S1). Canals were sequentially enlarged with rotary instruments up to sizes 30/0.04
(S2) and 30/0.06 (S3). The dentin thickness was measured at 0.1-mm intervals after
each preparation step (n = 2964 slices). Root level and position of the DZ were also recorded. Data were compared
using analysis of variance with Bonferroni pairwise comparison, Cochran's Q method,
and Pearson's test (α = 5%).
Results
Comparing the specimens before (S1) and after (S2 and S3) preparations showed a significant
reduction in the thickness of the DZ (P < .05), as well as between S2 and S3 steps (P < .05). At S1, the DZ was mostly located in the middle third of the root, but after
preparation, it shifted toward the coronal direction (P < .05). Both S2 (P = .004, r = 0.508) and S3 (P = .004, r = 0.506) preparation steps showed a positive correlation between canal
length and the root level of the DZ. At S1, the DZ was positioned toward the distal
and mesial in 73.4% (n = 22) and 26.6% (n = 8) of the specimens, respectively. After S3, the number of specimens with DZ positioned
toward the mesial aspect of the root significantly reduced to 3.3% (n = 1), whereas none of the specimens with DZ positioned toward the distal changed
its position after root canal enlargements (P > .05).
Conclusion
Overall, the enlargement of mesial canals of mandibular first molars with final instruments
sizes 30/0.04 and 30/0.06 affected the thickness, root level, and position of the
DZ.
Key Words
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Article info
Publication history
Published online: February 23, 2023
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 American Association of Endodontists.
