Keywords
Endodontic - filling materials - retreatment - root canal
Introduction
Endodontic retreatment aims to ensure complete removal of filling material (RFM) and
to eliminate necrotic debris and remaining microorganisms to reestablish the health
and normal conditions of the periapical tissues.[[1]],[[2]],[[3]] Retreatment is indicated when failure of primary endodontic treatment occurs, which
can be due to technical failures, complexity of the root anatomy, and/or persistence
of infection in the apical portion of the root canal.[[4]],[[5]]
Different techniques have been proposed for performing the RFM during retreatment,
including the use of continuous motion rotary instruments such as the ProTaper Universal
Retreatment (ProTaper-R) (Dentsply Maillefer, Ballaigues, Switzerland), Mtwo Retreatment
(Mtwo-R) (VDW, Munich, Germany), D-RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland),
and R-Endo (Micro-Mega, Besançon, France), and those with reciprocating movement including
Reciproc (VDW, Munich, Germany), Reciproc Blue (VDW, Munich, Germany), and WaveOne
Gold (Dentsply Maillefer, Ballaigues, Switzerland). Such instruments are generally
employed because of the decrease in working time associated with their use versus
that of hand files.[[6]],[[7]],[[8]],[[9]] However, there is no consensus to date on the effectiveness of rotary instruments
as compared with hand files in RFM.[[6]],[[7]],[[8]],[[9]],[[10]]
During RFM, the extrusion of the filling material, necrotic pulp tissue, microorganisms,
and irrigators to the periapical[[11]] can occur causing irritation in the periapical tissues, postoperative pain, and
difficulty in repairing the periapical tissue.[[12]],[[13]] In general, apical debris extrusion occurs in RFM regardless of the technique,
motion, and type of instrument used.[[14]],[[15]],[[16]],[[17]],[[18]],[[19]],[[20]],[[21]],[[22]],[[23]],[[24]]
There is no consensus regarding the apical debris extrusion caused by hand and rotary
techniques. Chandrasekar et al.[[17]] verified that the hand files caused less debris extrusion compared to the rotary.
However, other authors observed that the hand files caused more debris extrusion compared
to the rotary.[[14]],[[16]] There is also a divergence of findings of apical debris extrusion caused by the
employment of different kinematics systems.[[15]],[[18]],[[25]] Dincer et al.[[18]] and Silva et al.[[15]] observed that reciprocating instruments extruded less than continuous rotations,
whereas Çanakçi et al.[[25]] reported the opposite. Thus, the aim of the present study was to evaluate apical
debris extrusion during RFM performed by the ProTaper-R, Mtwo-R, Reciproc, and hand
files.
Materials and Methods
This study was approved by the Local Ethics Committee (protocol No. 44100015700005257).
Sixty human premolars with a single canal, fully formed apex, and curve up to 25°[[26]] were selected. Teeth with incomplete root formation, resorption, calcification,
or previous endodontic treatment were excluded. Thereafter, X-rays in the buccolingual
and mesiodistal directions were carried out.
The access cavity was prepared using diamond drills under constant irrigation. A size
10 K-file (VDW, Munich, Germany) was then introduced passively into the canal until
the tip was flush with the root surface. The working length (WL) was determined 1 mm
shorter than that measurement.
All canals were prepared with ProTaper Universal (Dentsply-Maillefer, Ballaigues,
Switzerland) nickel–titanium rotary files according to the manufacturer's recommendations,
through the use of the X-Smart Plus (Dentsply-Maillefer, Ballaigues, Switzerland)
endodontic motor. Irrigation with 2 mL of 5.25% sodium hypochlorite was performed
after each instrument. The F3 instrument was the last used in the WL. At the end of
the instrumentation, the canal was irrigated with 2 mL of 17% ethylenediaminetetraacetic
acid for 3 min; subsequently, the canal was irrigated with 5 mL of 5.25% sodium hypochlorite,
and a final irrigation with 5 ml distilled water was performed. The root canals were
dried with paper points and an association of the Continuous Wave Compaction technique
and the hybrid Tagger technique was used to fill the canals with gutta-percha F3 cones
of the ProTaper system and AH Plus root canal Sealer (Dentsply-Maillefer, Ballaigues,
Switzerland).
The filling compaction was confirmed by orthogonal and 90° angled X-ray. The teeth
with bubbles and voids in the filling material were discarded. Following the temporary
restoration of access cavities with a zinc-oxide-based shutter, the teeth were stored
in an incubator at 37°C with 100% humidity for 7 weeks to allow for complete setting
of the sealer.
Retreatment
At the end of the storage period, the dental crown was removed from the samples and
the roots standardized to 13 mm of total length. All steps were performed by a single
operator. Before the use of the files, the filling material was removed from the initial
3 mm of the canal with Gates Glidden drills (Dentsply-Maillefer, Ballaigues, Switzerland),
in order to facilitate the penetration of instruments.
During the retreatment phase, no solvent was used; instead, only 2 mL of 5.25% sodium
hypochlorite solution was used as the irrigating solution after each instrument. Instruments
were used only in three canals and then discarded. There was a criteria used to indicate
that an instance of RFM with one instrument was finished and that the next instrument
should be started. The criteria were as follows: Active part of the instrument seen
without debris after its removal from the canal; free penetration of instruments to
patency without interference; and absence of gutta-percha in the walls of the canal
observed by an optical microscope (D. Vasconcelos, São Paulo, SP, Brazil) with ×25
magnifying.
The instruments were used in an X-Smart Plus endodontic motor (Dentsply-Maillefer,
Ballaigues, Switzerland). The Mtwo-R and ProTaper-R systems were used with individual
torque and speed according to the manufacturer's recommendations, whereas Reciproc
was used with reciprocating motion. The RFM sequences were as follows:
-
Mtwo-R group: Instrument R25/.05 was used in the middle and cervical thirds with brushing
motion on the walls of the canal, after the same instrument was used with a gentle
in-and-out motion to reach the WL
-
ProTaper-R group: The D1 instrument was used in the cervical third, in the first 4 mm
passively, whereas the D2 instrument was used with brushing motion to the middle third
and the D3 applied gentle pressure to the WL
-
Reciproc group: The R25 instrument was used to penetrate the filling material with
an in-and-out motion to the WL
-
Hand file group: Type K and Hedstroem hand files were used in a “crown-down” sequence
for gutta-percha removal to 3 mm short of the WL. After a size 15 K-file (Dentsply-Maillefer)
was employed to open the space until the proximity of the WL, sizes 20, 25, and 30
K-files were used sequentially and were intercalated with H-files of a similar diameter
to seize the gutta-percha and remove it.
Evaluation of debris extrusion
The extruded debris were collected in a preweighed Eppendorf tube attached to the
lower edge of an individual silicone plug prepared for each tooth according the method
described by Myers and Montgomery.[[27]] After removing the dental crown, the root apex was suspended by the cervical within
the receptor tube. A second tube was used to hold the device during instrumentation.
A disposable 27-gauge needle was inserted into the silicone plug, simulating a cannula,
to balance the internal and external pressures. The Eppendorf tubes were sealed so
that the operator could not observe the contents inside. In all groups, after RFM,
the root was removed from the Eppendorf tube and the debris adhered to the outside
of the root was collected by washing the root with 1 mL of distilled water inside
the tube. The tubes were then placed in a dry heat oven at 37°C for 7 days to stimulate
the evaporation of the irrigation solution.
A high-precision analytical balance (model FA-2104N; Bioprecisa, Brazil) with an accuracy
of 10−4 g was used to evaluate the tubes before and after the instrumentation. The initial
weighing of the Eppendorf tube was done before the tooth root was inserted and attached
to the Eppendorf tube. The final weighing was completed after instrumentation, root
removal from the Eppendorf tube, irrigation of the outside of the root, and drying.
Three weighing sessions were performed and a mean was obtained for the initial and
final weights. A single independent operator performed the weighing. The apical extrusion
of debris was determined by the difference of the final dry weight average and the
mean initial weight of each sample.
Statistical analysis
Data analysis was performed using the Statistical Package for the Social Sciences
version 2.0 program (IBM Corp., Armonk, NY, USA). The data were analyzed by a blind
and independent evaluator. The mean apical debris extrusion in grams was calculated
for each group. The difference between the groups was analyzed statistically by the
ANOVA variance test with Tukey's test (P < 0.05).
Results
In the Mtwo-R group, two samples were discarded due to instrument fracture during
RFM of the middle third. The occurrence of perforations was not observed in any of
the tested groups. Apical debris extrusion occurred in all groups [[Table 1]]. The Mtwo-R group produced significantly more extrusion than did the ProTaper-R
and Reciproc groups (P < 0.05); however, there was no significant difference between the Reciproc, ProTaper-R
and hand file groups (P > 0.05).
Table 1:
Amount of apical debris extrusion (g)
|
Apical debris extrusion
|
Mtwo-R
|
ProTaper-R
|
Reciproc
|
Hand file
|
|
Mean±SD
|
0.1112±0.1255
|
0.0605±0.0053
|
0.0038±0.0045
|
0.0432±0.0795
|
|
Minimum
|
0.0041
|
0.0003
|
0.0002
|
0.0015
|
|
Maximum
|
0.3624
|
0.0216
|
0.0170
|
0.2461
|
Mtwo-R – Mtwo retreatment, ProTaper-R – ProTaper Universal Retreatment, SD – Standard
deviation
Discussion
During RFM, endodontic maneuvers should be performed to minimize apical debris extrusion
and thus avoid flare-up.[[13]] In light of this, the present study aimed to evaluate the apical debris extrusion
during RFM performed by different systems. It was verified that all four systems evaluated
caused apical debris extrusion during RFM. However, the Mtwo-R group produced significantly
more extrusion in comparison with the ProTaper-R and Reciproc groups.
The method used here for the evaluation of debris extrusion was proposed by Myers
and Montgomery.[[27]] Although this method presents limitations due to the lack of inverse pressure,
which would simulate the periodontal ligament, it is still widely used for such an
evaluation.[[14]],[[15]],[[19]],[[25]],[[28]] Studies used distilled water as an irrigating substance because sodium hypochlorite
forms crystals of sodium that can be added to the weight of the extruded debris apically.[[18]],[[28]] However, as well as other studies,[[14]],[[25]] we have chosen to use it to simulate more faithfully the clinical situation, because
sodium hypochlorite is a widely used irrigating substance.
For standardization of the samples, we used mandibular premolars with a single straight
canal and performed preinstrumentation of all samples with the ProTaper Universal
system, ending with the F3 file. In addition, the removal of the dental crown and
establishment of equal root lengths for all groups was completed.
The results of the present study revealed that all of the systems caused apical debris
extrusion, which corroborated with previous findings.[[14]],[[15]],[[16]],[[17]],[[18]],[[19]],[[20]],[[21]],[[22]],[[23]],[[24]] When comparing the groups to one another, this study showed that Mtwo-R instruments
caused a significantly greater amount of apical debris extrusion than the Reciproc
and ProTaper-R instruments. A similar study also observed that the Mtwo-R group showed
more extrusion as compared with the Reciproc group; however, unlike in the case of
our findings, no difference was found between the Mtwo, ProTaper-R, and hand files
in this previous study.[[18]] We believe that this discrepancy with our results is related to the final instrumentation
performed after RFM used by Dincer et al.[[18]] In the present study, we evaluated only the apical debris extrusion caused by RFM.
Contrary to the results obtained here, Lu et al.[[14]] determined that Reciproc extruded significantly more than Mtwo-R. According to
the authors, the reciprocating motion allows the instrument to advance continuously
forward and such an action may push debris toward the apex. Separately, Çiçek et al.[[21]] observed no difference in the characteristics of debris extrusion between the ProTaper-R
and Mtwo-R systems. These discrepancies as compared with our findings may be related
to a difference in the filling technique performed before RFM, the irrigating substance
used, and/or the choice of the instruments size used in RFM in relation to the canal
diameter.
It was verified in the present study that there was no significant difference between
the Reciproc, ProTaper-R, and hand file groups. Thus, although some studies suggest
that the use of hand files causes greater apical debris extrusion when compared with
rotary use[[14]],[[16]],[[29]] or the inverse,[[17]] we cannot in good faith suggest this based on our results. Similarly, we cannot
confirm the hypothesis that the kinematics of the movement may influence the apical
debris extrusion,[[14]],[[30]] because the ProTaper-R system, a continuous rotary system, did not lead to a significant
difference when compared with a reciprocating system. We agree with another study
that reported that instrument design plays an important role in the amount of debris
extruded apically.[[29]]
The tip of the last instruments used during RFM of Mtwo-R, ProTaper-R, Reciproc, and
hand file groups had nominal diameters of 0.25 mm, 0.20 mm, 0.25 mm, and 0.30 mm,
respectively. Although the tip diameter difference between the instruments used in
the four groups varied in size between 0.05 mm and 0.1 mm, no difference was found
between the ProTaper-R, Reciproc, and hand file groups. The Mtwo-R group extruded
more than the other groups independently of having a similar sized tip diameter or
not. In addition, we used instruments with such diameters because the ProTaper-R provides
only one instrument to clear the apical third and among the instruments available
from the Mtwo-R and Reciproc lines, the ones used were compatible with the tip diameter
of the instrument F3 used in the instrumentation that preceded the canal filling.
Thus, they are compatible with the apical diameter of the canal.
Conclusions
All four systems caused apical debris extrusion during RFM. The Mtwo-R group produced
significantly more debris extrusion than did the ProTaper-R and Reciproc groups. There
were no differences among the Reciproc, Protaper-R, and hand file groups.
