A comparative evaluation of different retreatment methods on apical root microcracks initiation and propagation: An in vitro study

Aim: This study aims to evaluate and compare the effect of Hedstrom files, ProTaper Universal retreatment files, D-Race retreatment files, and Clearsonic retreatment tips on apical root microcrack initiation, propagation during retreatment procedure. Methods: Fifty-six extracted mandibular premolar were selected. Canals were enlarged to F3 size using ProTaper universal rotary system followed by obturation. The samples were divided into four groups ( n = 14) according to different retreatment methods used. In group 1, retreatment was performed using Hedstrom files. In group 2, ProTaper Universal retreatment files were used. In group 3, D-Race retreatment file were used. In group 4, Clearsonic retreatment tip was used. Additional instrumentation was done with F4 ProTaper universal file for all four groups. Digital images of the apical root surface were recorded under stereomicroscope (×45) for microcrack initiation and propagation, before preparation, after biomechanical preparation, after obturation, after retreatment, and after additional instrumentation. Results: Statistically significant difference ( P < 0.05) was seen between the groups regarding the initiation of microcracks after use of retreatment instruments. Group 2 exhibited significantly greater crack initiation compared to group 1 and 4 ( P = 0.049). In Hedstrom file group, 28.6% of teeth (4 out of 14 teeth) showed dentinal defects. In ProTaper retreatment files group, 64.3% of teeth (9 out of 14 teeth) showed dentinal defects. In D race retreatment file group, 35.7% of teeth (5 out of 14 teeth) showed dentinal defects. Finally in Clearsonic retreatment tip group, 28.6% of teeth (4 out of 14 teeth) showed dentinal defects. Conclusion: This study demonstrated that retreatment procedure and apical enlargement after use of retreatment files can cause initiation and propagation of apical root microcrack. Retreatment files having progressive taper and larger core diameter such as ProTaper universal retreatment files resulted in the highest number of microcracks. In contrast, the Clearsonic retreatment tip and Hedstrom files group resulted in least number of root microcracks initiation and propagation.