Abstract:

Objective: The purpose of this in-vitro study was to investigate the residual root canal filling material after retreatment of root canals using stainless steel hand files, and four nickel-titanium retreatment instruments. Materials and methods: Seventy five extracted mandibular premolars were instrumented and filled. The samples were randomly divided into 5 groups (n=15) and retreated using Hedström files, Mtwo R, R-Endo, ProTaper Universal Retreatment, and D-RaCe systems. The roots were digitally radiographed, then grooved split longitudinally to investigate the area of remaining filling material. The time of retreatment and the instruments fracture were also recorded. Results: The Hedström files left less filling material than the rotary retreatment instruments but a significant difference was found only in the middle third (p< 0.01). The apical third had the most residual gutta-percha and sealer compared to the coronal and middle thirds. The retreatment time for the D-RaCe and ProTaper Universal Retreatment groups were significantly shorter than other groups (p< 0.01). Eight Mtwo R files, 2 ProTaper Universal Retreatment files and 1 R-Endo file were fractured. Conclusion: All groups left residual root canal filling material inside the root canal walls. Nickel-titanium rotary retreatment instruments were faster than Hedström files but had a higher risk of instruments fracture. 

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