| Abstract (english) | 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. |
