Abstract
The purpose of this study was to compare the incidence and longitudinal propagation of dentin defects after gutta-percha removal with hand and rotary instruments using microcomputed tomography. Twenty mandibular incisors were prepared using the balanced-force technique and scanned in a 19.9 μm resolution. Following filling with the lateral compaction technique, gutta-percha was removed with ProTaper Universal Retreatment (PTUR) or hand instruments. After rescanning, a total of 24,120 cross-sectional images were analyzed. The numbers, types, and longitudinal length changes of defects were recorded. Defects were observed in 36.90% of the cross sections. A total of 73 defects were comprised of 87.67% craze lines, 2.73% partial cracks, and 9.58% fractures. No significant difference in terms of new defect formation was detected between the retreatment groups. The apical and middle portions of the roots had more dentin defects than the coronal portions. Defects in three roots of the PTUR instrument group increased in length. Under the conditions of this in vitro study, gutta-percha removal seemed to not increase the incidence of dentin defect formation, but the longitudinal defect propagation finding suggests possible cumulative dentinal damage due to additional endodontic procedures. Hand and rotary instrumentation techniques caused similar dentin defect formation during root canal retreatment.
Highlights
Vertical root fractures (VRFs) are associated with a poor prognosis for the affected tooth [1] and should be prevented
Dentin defects, which can be created by endodontic procedures [3, 4], may act as stress concentration areas [2], propagate from repeated stresses generated as a result of further endodontic and restorative procedures [2, 5], and develop into a VRF
Only a few studies have investigated the effect of root canal retreatment procedures on the extent of dentin damage
Summary
Vertical root fractures (VRFs) are associated with a poor prognosis for the affected tooth [1] and should be prevented. Only a few studies have investigated the effect of root canal retreatment procedures on the extent of dentin damage. A more recent methodology, microcomputed tomographic (micro-CT) imaging, allows for nondestructive volumetric quantitative and qualitative assessments with accurate comparisons of defects in the same specimen before and after endodontic procedures.
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