The main reason for endodontic failure is the persistence or regrowth of microorganisms that have a high affinity for root canal filling materials and sealers, especially gutta­percha. The reasons for these microbial issues range from inadequate control of aseptic conditions and overlooked root canals to improper instrumentation and complications during root canal treatment occurring in the form of perforations, broken instruments, short or overextended root canal fillings, and microleakage of temporary or long­term restorations. Endodontic failure may require either nonsurgical or surgical retreatment, where nonsurgical root canal retreatment is the preferred option whenever possible. Proper retreatment can be challenging and time­consuming; however, removing the old root canal filling is essential as it acts as a mechanical barrier to the irrigating solution used in the retreatment process. Depending on their chemical composition, sealers can be classified as either zinc­oxide eugenol, epoxy resin, silicon, calcium hydroxide, glass ionomer, methacrylate resin, or calcium silicate types. In 2007, bioceramic sealers were introduced as a new sealer type. The chemical reaction of bioceramic sealers utilizes the moisture in dentine tubules to form a calcium silicate hydrate gel and portlandite, which reacts with the moisture in dentine tubules forming calcium silicate hydrate gel and portlandite. The result is a tag­like structure providing adhesion of bioceramic materials to the root canal dentine. This interaction facilitates successful sealing, but it may also hinder the complete removal of the root canal filling if retreatment is needed. Different techniques have also been developed to improve the sealing of the endodontic space. Single cone and carrier­based techniques have been developed to offer a possible solution to cold lateral compaction where vertical fractures can occur due to forces applied during obturation. Both techniques are usually used after root canal instrumentation with NiTi enginedriven files, and both techniques have several advantages, including simplicity and small time expenditures, while also eliminating the requirement for accessory cones or time spent on lateral condensation. A recently introduced obturation technique is GuttaFussion (VDW, Munich, Germany). It consists of a plastic core coated with cross­linked thermoset gutta­percha that does not melt at the temperatures generated by the special oven. Irrigation after mechanical debridement is a crucial step in the retreatment process and has been improved by introducing various irrigation activation techniques. The philosophy behind this approach is that increasing the turbulence of the irrigating solution improves the debridement of the root canal system and thereby improves the penetration of the fluid to enhance antibacterial action. The use of lasers has been shown to achieve a similar effect. Laser­activated irrigation (LAI) is based on the creation of intracanal cavitation as a result of photoacoustic and photomechanical effects. This effect is linked to the absorption of the energy emitted by erbium lasers, as it agitates the water­based solutions in the intracanal space. More recently, Er:YAG laser modality, SWEEPS (Shock Wave Enhanced Emission Photoacoustic Streaming), was launched to improve the cleaning and disinfecting efficacy of LAI. However, to date, little information is available regarding the effectiveness of removing root canal filling material during retreatment using SWEEPS. The available literature contains no research on the effectiveness of SWEEPS in removing epoxy resin– based and bioceramic sealers in combination with single cone and core­carrier obturation techniques. Therefore, the present study aimed to use micro­computed tomography (micro­CT) analysis to evaluate the efficacy of shock wave–enhanced emission photoacoustic streaming (SWEEPS) in the retreatment of epoxy resin­based and bioceramic sealers used in combination with single­cone and carrier­based obturation techniques. Methodology: This study included 76 single­rooted extracted human teeth with single canals, and intact and mature root apices were selected. After removing the contaminated tissue on the outer specimen surfaces, the working length of each root canal was determined by inserting a size #15 K file. The crowns were sectioned using a water­cooled diamond drill to obtain roots with a standardized length of 17 mm. The root canals were instrumented using a size R25 Reciproc instrument and a VDW Gold endo motor according to the manufacturer’s instructions. During instrumentation, the canals were irrigated with 2.5% NaOCl solution using a 27­gauge needle and a 2 mL syringe. The smear layer was removed by rinsing the root canals with 2 mL of 17% EDTA for 1 min, followed by a final rinse with saline solution. The canals were dried using size R25 Reciproc paper points. All specimens were randomly divided into four experimental groups according to the root canal obturation technique and the type of root canal sealer. For one of the single­cone groups (n = 19), a Reciproc R25 gutta­percha cone was dipped into the AH Plus sealer and then placed slowly, in an up­and­down motion, until it reached the entire working length. For the other single­cone group (n=19), a combination of bioceramic gutta­percha and bioceramic sealer was used for root canal filling. The TotalFill BC sealer was syringed into the canal, and TotalFill gutta­percha was placed in the canal up to the working length. The coronal excess of the master cone was cut to the coronal orifice using a flame­heated hand plugger. For one core­carrier group (n = 19), the root canal walls were coated with AH Plus sealer using a size #25 reamer in a counterclockwise motion. For the other core­carrier group (n = 19), MTA Fillapex sealer was used to coat the root canal walls. Guttafusion R25 was heated in a special oven during the coating of the canal with the root canal sealer. The heated gutta­percha was then slowly inserted to the working length without twisting or forcing. The excess material in the canal orifice was then extruded by bending the core­carrier to the right and left until separation took place, and the core material was condensed with a plugger by the same researcher. The access cavity in all specimens was sealed with glass ionomer cement. All specimens were stored at 37°C for one week to allow sufficient time for the sealer to set. After one week and complete setting of the sealer, the root canal retreatments were performed on all specimens (n = 76) using R25 Reciproc instruments in a VDW Gold endo motor according to the manufacturer’s instructions, without the use of any solvent. The root canals were rinsed with 2 mL of 2.5% NaOCl solution. The criteria for the completion of the retreatment procedure were smooth canal walls and no presence of root canal filling material on the Reciproc instruments. At the end of the retreatment procedure, root canals were rinsed with 2 mL of 17% EDTA for 1 min, followed by a final rinse with saline solution. The canals were then dried using size R25 Reciproc paper points. Auto SWEEPS protocol (50 μs, 15 Hz, 20 mJ, and 0.3 W) was performed for LAI using an Er:YAG laser with a 2940 nm wavelength. The pulp chamber was reconstructed using thermoplastic materials and served as a reservoir for the irrigation solution. The tip was submerged in saline and hovered above the orifice in the cervical region rather than inserting the tip into the canal. After retreatment using Reciproc instruments and additional SWEEPS treatment using micro­CT, each tooth was scanned after root canal filling. Once scanning was done, the images were reconstructed to determine the residual volume of the sealer. The results for the volumes of root canal filling after retreatment with the Reciproc instruments and the additional use of SWEEPS were subjected to linear transformation to remove the influence of the initial root canal filling volume. The differences between the four experimental groups were tested using analysis of variance. Results and discussion: The volume of root canal filling materials decreased significantly in all four experimental groups after retreatment with Reciproc instruments (p<0,05), however, none of the teeth showed complete removal of the root canal filling materials. No statistically significant difference was observed between the groups regarding the volume of root canal filling remnants after retreatment only with Reciproc instruments (p > 0,05). Additional treatment with SWEEPS significantly reduced the volume of root canal materials in all experimental groups compared to retreatment with Reciproc instruments alone (p < 0,05). However, none of the teeth, even with the SWEEPS treatment, showed complete removal of the material from the root canal. Statistical analysis of the effectiveness of SWEEPS according to the root canal filling technique or the root canal filling materials revealed a statistically significant difference for the single­cone group treated with the combination of AH Plus and gutta­percha, given that a higher volume of root canal filling remnants was observed in that group than in the other groups (p < 0,001). The findings of this study also reveal a more effective removal of a combination of bioceramic sealer and bioceramic gutta­percha than of the combination of epoxy resin­based sealer and gutta­percha after SWEEPS treatment of root canals obturated using the single­cone technique. Comparing the effectiveness of SWEEPS in the core­carrier groups did not show any statistically significant difference between the AH Plus and the bioceramic sealers. A comparison of AH sealer used with core­carrier and single cone techniques revealed a smaller residual volume in the core carrier after retreatment with SWEEPS. The groups treated with the bioceramic sealer combined with different obturation techniques showed no statistically significant differences in the root canal filling after SWEEPS treatment (p > 0,05). The results of this study show that the root canal filling materials were not completely removed from the root canal walls in any of the samples, regardless of the retreatment technique or irrigant agitation using SWEEPS. Conclusion: The results of this in vitro study indicated that none of the materials were completely removed from the root canal after an additional SWEEPS treatment. However, SWEEPS can be used to enhance the removal of both epoxy resin­based and bioceramic sealers in combination with single­cone and carrier­based obturation techniques. This information may be important for clinical use, given that reducing the root canal filling remnants to a minimum may be beneficial for the success of endodontic retreatment.