Comparison of the Effectiveness of Various Continuous Rotary and Reciprocating Systems to Remove Gutta-Percha and an Epoxy-based Sealer from Root Canals Using CBCT: An in Vitro Study

Abstract Aim: The aim of this in vitro study was to compare the effectiveness of four different continuous rotary and reciprocating retreatment systems—ProTaper Universal Retreatment, HyFlex Remover, WaveOne Gold, and Mtwo Retreatment files—in removing gutta-percha and epoxy resin-based sealer (AH Plus) from root canal walls, using Cone Beam Computed Tomography (CBCT) for volumetric analysis. Materials and Methods: Sixty extracted single-rooted mandibular premolars with fully formed apices were selected, instrumented using ProTaper Gold rotary files, and obturated with AH Plus sealer and ProTaper gutta-percha (F3 size) using the single-cone technique. Following a one-month incubation period at 37°C, specimens were randomly divided into four groups (n=15) and retreated using the designated systems. Pre- and post-retreatment CBCT scans were performed to evaluate the volume of residual filling material. Data were statistically analyzed using one-way ANOVA, Games-Howell post hoc tests, and paired t-tests (p < 0.05). Results: All systems demonstrated significant reduction in obturation material (p < 0.001), but none achieved complete removal. HyFlex Remover exhibited the lowest mean residual volume (5.76 ± 0.67 mm³), followed closely by ProTaper Universal (5.81 ± 0.37 mm³) and Mtwo (6.92 ± 0.50 mm³). WaveOne Gold showed the highest residual volume (7.51 ± 0.88 mm³), indicating the least efficacy. The differences among the groups were statistically significant (p = 0.001). Conclusion: Within the limitations of this CBCT-based in vitro study, HyFlex Remover was found to be the most effective system for removing gutta-percha and AH Plus sealer, while WaveOne Gold was the least effective. The performance of each system is influenced by factors such as file design, metallurgy, and motion dynamics. Complete removal remains a challenge, especially when epoxy resin-based sealers are used, emphasizing the need for continued advancements in retreatment strategies.