Solvent Effect on Post-Op Pain in Root Canal Retreatment

Clinical Oral Investigations
https://doi.org/10.1007/s00784-019-02948-3
ORIGINAL ARTICLE
Effect of solvent use on postoperative pain in root canal retreatment:
a randomized, controlled clinical trial
Ozgur Genc Sen 1
1
& Ali Erdemir & Burhan Can Canakci
2
Received: 4 January 2019 / Accepted: 3 May 2019
# Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Objectives The aim of this randomized clinical trial was to assess the effect of solvent use during the removal of root canal filling
on postoperative pain after retreatment.
Materials and methods Ninety patients scheduled for root canal retreatment were randomly assigned to one of the following two
groups according to the root canal filling removal procedure used: ProTaper retreatment (Dentsply Maillefer, Ballaigues,
Switzerland) instruments or ProTaper retreatment instruments in combination with gutta-percha solvent. A single operator
performed the retreatments in a single visit. The incidence and intensity of the postoperative pain were rated on a numeric rating
scale by patients at 24, 48, and 72 h after retreatment. The analgesic tablet intake number was also recorded. Data were analyzed
using Mann‑Whitney U, Wilcoxon, and chi-square tests.
Results For the intensity of postoperative pain, the difference between the two groups was not statistically significant. Moreover,
no statistically significant difference was found between the two groups in terms of analgesic medication intake (P > 0.05).
Conclusions The processes involving the use and non-use of a solvent in the removal of root canal fillings were found to be
equivalent in terms of postoperative pain intensity and analgesic intake.
Clinical relevance Some in vitro studies claimed that the use of a gutta-percha solvent in the removal of root canal fillings tends to
reduce postoperative pain since extrusion of debris was significantly less. This randomized clinical trial indicates that the removal
of root canal fillings with or without the use of a solvent was associated with equivalent postoperative pain intensity and analgesic
intake.
This study is registered in the www.ClinicalTrials.gov database with the identifier number NCT03756363.
Keywords Postoperative pain . Root canal retreatment . Solvent
Introduction
Although postoperative pain cannot be directly correlated
with the long-term success of root canal treatment, its control
is of great importance for patient and physician satisfaction.
Retreatment is considered to be a contributing factor for postoperative complications, since it includes a number of
* Ozgur Genc Sen
[email protected]
1
Department of Endodontics, Faculty of Dentistry, Van Yuzuncu Yil
University Zeve Campus, Bardakci Mahallesi, 65080 Tuşpa, Van,
Turkey
2
Department of Endodontics, Faculty of Dentistry, Trakya University
Balkan Campus, 2213 Iskender Koyu, Edirne, Turkey
laborious procedures and requires overcoming the difficulties
associated with the previous root canal treatment. Removing
the initial root canal filling completely is fundamental in order
to perform appropriate cleaning, shaping, and obturation.
During the removal of root canal filling material, guttapercha (GP), necrotic tissue remnants, dentinal chips,
irrigants, and microbes may extrude from the apical foramen
and gain access to periapical tissues, which may lead to postoperative complications and/or treatment failure [1, 2].
Unfortunately, all available techniques and instruments are
associated with apical extrusion of debris to some degree during the root canal preparation or removal of the root canal
fillings [3–8].
Several techniques such as stainless steel hand files, nickeltitanium (NiTi) rotary instruments, ultrasonics, heat-bearing
instruments, and lasers have been used to remove GP from
root canals [9, 10]. In combination with these procedures,
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chemical solvents are recommended to facilitate the removal
of gutta-percha by softening [11]. Some of the frequently investigated and used organic solvents in endodontics are chloroform, xylene, eucalyptol, halothane, orange oil, and turpentine [12–15]. Guttasolv (Septodont), a eucalyptol-based solvent, has been the choice of many professionals since it is
biocompatible and safe [16].
ProTaper Universal retreatment (PTUR) instruments
(Dentsply Maillefer, Ballaigues, Switzerland) were specifically developed for, and were proven to be effective in, removing
root canal fillings [17–19]. The system consists of three progressively tapered rotary files, which have a convex triangular
cross-sectional design [20]. The D1 instrument (tip 30, taper
0.09) facilitates the initial penetration into the filling material.
The D2 instrument (tip 25, taper 0.08) is used for the removal
of the filling material at the middle third of the canal. The D3
instrument (tip 20, taper 0.07) is used for the removal of the
remaining part of the filling material up to the working length
[17].
Scientific literature contains a few studies on the amount of
apically extruded debris with and without the use of solvent
with rotary instruments. It was reported that the use of PTUR
instruments in combination with gutta-percha solvent reduced
the amount of apically extruded debris compared with their
use in a solvent-free process [21, 22]. Nevertheless, clinical
studies on the comparison of postoperative pain after root
canal filling removal with or without solvent remain to be
published. The aim of this study was to evaluate the effect
of combined use of PTUR instruments and Guttasolv solvent
on postoperative pain intensity after retreatment.
Materials and methods
The Institutional Ethics Committee office of Invasive Clinical
trials approved the protocol of this randomized clinical trial
(number 13.11.2018-06). The research was conducted in accordance with the Declaration of Helsinki. Before participation, all patients had read and signed an informed consent
form, which describes the details, benefits, and risks of the
treatment procedures.
Patient selection and allocation
The adult patients (18–59 years of age) who were referred to
the Department of Endodontics with a diagnosis of failed root
canal treatment were examined radiographically and clinically. Clinically asymptomatic, single-rooted, single-canaled
teeth that had an initial root canal filling 2–4 mm short from
the apex were selected. Only the teeth exhibiting radiographic
evidence of well-defined periapical radiolucency (periapical
index = 4 [23]) were included. Since the healing process of
apical periodontitis may take up to 4 years [24], teeth in which
root canal fillings were performed at least 4 years prior were
selected. The exclusion criteria were as follows: patients who
did not meet the abovementioned criteria; teeth with sinus
tracts; teeth with intraradicular posts; teeth with overfilled root
canals; presence of other teeth requiring treatments; presence
of any pain disorders or systemic disease; pregnancy; utilization of antibiotics or analgesics within the last 1 month. Ninety
cases were selected on the basis of the determined inclusion
criteria and randomly allocated to two groups (n = 45). For a
randomized selection, sealed envelopes containing group
codes were placed in a bag, and a graduate student blinded
to the study removed an envelope from the bag and reported
the code to the physician before each treatment.
Retreatment protocol
A single operator completed all retreatment procedures in one
session. The patients were anesthetized with 40 mg of Articain
+ 0.006 mg/mL epinephrine (Ultracain DS Forte; Aventis,
Istanbul, Turkey). After isolation of the teeth with rubber
dam, coronal restorations were removed using sterile highspeed burs until the access of the root canals become visible.
The coronal 3 mm of the root canal fillings were removed
using size 3 Gates-Gidden drills.
Non-solvent group
PTUR instruments were used in conjunction with an X-Smart
electric motor (Dentsply Maillefer, Ballaigues, Switzerland)
for the removal of root canal fillings. D1, D2, and D3 instruments were used respectively with a full rotational motion
(500 rpm speed and 2 N/cm torque) until the working length
was reached.
Sample size calculation
Solvent group
The sample size calculation based on data obtained from a
pilot study indicated that 38 patients would be sufficient per
group (type-1 alpha error = 5%, effect size = 0.7, power =
80%). In order to compensate for possible participant dropouts
during the treatment and/or follow up period, in this study, 45
patients were assigned per group.
PTUR instruments were used with the abovementioned technique. However, unlike for the first group, 0.05 mL of solvent
was placed in the root canal just prior to the use of D1, D2, and
D3 instruments and retained for 1 min. Thus, a total of
0.045 mL of solvent was used per canal.
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The working length of each tooth was determined via
Propex Pixi apex locator (Dentsply Maillefer, Ballaigues,
Switzerland) and confirmed using digital periapical radiography. When the D3 instrument easily reached the working
length and no further obturation material could be seen on
the instrument or in the irrigant, periapical radiography was
performed to determine the completion of root canal filling
removal. For final apical enlargement, #40, #45, or larger sizes
(#50, #60) of stainless steel K-files were used depending on
the foramen size and type of teeth. The patency of the apical
foramen was verified using a #10 K-file beyond the apex.
During the root canal filling removal and instrumentation
procedures, 2.5% NaOCl irrigation was performed using a 30gauge side-vented syringe (Max-i-Probe; Dentsply Rinn,
Elgin, IL, USA) after the use of each file. The canals were
dried by aspiration and using absorbent paper points before
every application of the solvent.
Finally, all canals were irrigated using 3 mL 2.5% NaOCl,
3 mL 17% EDTA, 3 mL 2.5% NaOCl, and 5 mL of physiological saline solution sequentially. Thereafter, root canals
were dried with paper points and obturated using a lateral
compaction technique with gutta-percha cones and an epoxy
resin-based root canal sealer (MM-Seal, Micromega,
Besançon, France). The coronal cavities were restored using
a one-step self-etch adhesive G-Premio Bond (GC Corp.,
Tokyo, Japan) and a hybrid composite resin (Filtek Z250,
3 M ESPE, St Paul, MN, US).
Assessment of postoperative pain
The degree of the postoperative pain was measured using an
11-level numeric rating scale (NRS) at 24, 48, and 72 h following the retreatment. The NRS is a segmented numeric
version of the visual analog scale (VAS) and consists of successive numbers from 0 to 10 on a horizontal line. The respondent selects a number that best represents the intensity of his
pain. Number B0^ represents Bno pain^ whereas number B10^
represents Bthe worst pain imaginable^ [25, 26].
A form was provided to the patients along with the NRS
and they were instructed to mark the number that best reflects
the sensation of pain intensity in the first, second, and third
postoperative days. The patients were advised to take an analgesic tablet (400 mg Ibuprofen) in case of severe pain, at 6-h
intervals. They also were requested to record the number of
analgesic pills consumed each day. The forms were collected
on the 4th day following the retreatment.
Statistical analysis
All statistical analyses were performed using SPSS 13.0 for
windows (SPSS Inc., Chicago, IL, USA). Continuous
variables were presented as means with standard deviations,
whereas categorical variables were presented as numbers and
percentages. The Mann‑Whitney U test was used to compare
the two groups in terms of continuous variables. The
Wilcoxon test was used for within-group comparisons among
the different time periods. The chi-square test was performed
to determine the relationships between categorical variables.
A P value of < 0.05 was considered statistically significant.
Results
Two patients from the non-solvent group were excluded due
to the presence of pre-existing ledges that hindered access to
the working length. Thus, data from a total of 88 patients were
included in the statistical analysis (Fig. 1). Statistical analysis
of baseline and clinical features (age, sex, tooth localization)
of the non-solvent and solvent groups showed no significant
differences (Table 1). Overall, within the same group, sex and
tooth localization had no influence on postoperative pain for
both groups.
The mean NRS scores of postoperative pain at different
time periods for the non-solvent and solvent groups are shown
in Table 2. Differences between the two groups at all time
intervals were not statistically significant. No statistically significant difference was found between the two groups in terms
of analgesic medication intake (Mann‑Whitney U test,
P > 0.05).
In both groups, the highest NRS scores were recorded on
the first day, which then decreased on the following 2 days.
Statistically significant differences were found between the
two groups among the time periods for each group in terms
of postoperative pain intensity (Wilcoxon test, P < 0.05). In
both groups, postoperative pain was comparable between the
first and second days after treatment (Pnon-solvent = 0.091
and Psolvent = 0.38). The pain on the third day was significantly less than that on the first two days in the non-solvent
(P3rd-1st = 0.001 and P3rd-2nd = 0.001) and solvent (P3rd1st = 0.009 and P3rd-2nd = 0.019) groups.
Discussion
In vitro studies have reported that solvent usage in the removal
of root canal fillings result in significantly less extruded debris
(compared with the non-use of solvent) and therefore could
provide reduction in postoperative pain [21, 22]. Because
there is no clinical evidence regarding the subject, the present
randomized clinical trial aimed to determine the effect of solvent use on postoperative pain intensity in endodontic
retreatments. Although higher postoperative pain values were
observed in the non-solvent group compared with the solvent
group, the difference was not statistically significant. The
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Enrollment
Assessed for eligibility (n= 185)
Excluded (n= 95)
Not meeting inclusion criteria (n=85)
Declined to participate (n=10)
Randomized (n= 90)
Allocation
Solvent group (n= 45)
Received allocated intervention (n= 45)
Non-solvent group (n=45)
Received allocated intervention (n= 43)
Did not receive allocated intervention (n=0)
Did not receive allocated intervention
(pre-existing ledge hindered instrumentation (n=2)
Follow-Up
Lost to follow-up (n= 0)
Lost to follow-up (n= 0)
Analysis
Analysed (n= 43)
Analysed (n= 45)
Fig. 1 The CONSORT flow diagram for randomized clinical trials
discrepancy of the statistical significance between in vitro extrusion studies and this study could be attributed to the presence of physical backpressure provided by periapical tissues
in clinical conditions.
It is also important to point out that root canals of the teeth
in the abovementioned studies were obturated 1 mm short of
the apical foramen, whereas the root canal filling in the present
study was 2–4 mm short of the root apex. The longer distance
between the root canal filling and the root apex may have
induced a limited amount of material extrusion into the
periapical tissues; this factor may have been the reason for
Table 1 Baseline demographic
and clinical features of the
patients in the two groups
Demographic and clinical features
Gender
Male
Female
Tooth localization
Maxillary
Mandibulary
Mean Age (in years)
Preoperative pain
similar postoperative pain levels in the non-solvent and solvent groups.
The obtained results indicated a low incidence of postoperative pain; this finding was consistent with those of other
studies [27–29]. Moreover, this finding could be attributed to
the proper procedures and adequate chemomechanical instrumentation of the root canals with maximal reduction of risk of
iatrogenic and procedural errors. The working length of the
root canals was determined using the Propex Pixi apex
locator—the reliability of which has been documented in the
literature [30]—and confirmed radiographically. The root
Non-solvent n (%)
Solvent n (%)
P value
18 (41.5)
25 (58.1)
15 (33.3)
30 (66.7)
0.409
25 (58.1)
18 (41.9)
42
None
27 (60)
18 (40)
38
None
0.859
0.45
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Table 2 Mean postoperative pain values (mean ± SD) at the tested time
periods, number of analgesic pills consumed over 3 days and p values
Non-solvent (n = 43)
Mean ± SD
Solvent (n = 45)
Mean ± SD
*P value
Pain on 1st day
2.33 ± 3.22a
Pain on 2nd day
Pain on 3rd day
Analgesic intake
2.05 ± 3.27a
1.21 ± 2.57b
0.86 ± 1.92
1.44 ± 2.14a
1.22 ± 2.57a
0.64 ± 1.71b
0.40
0.14
0.34
0.47 ± 0.99
0.99
*The differences between two groups were not statistically significant
(Mann‑Whitney U test, p > 0.05)
a, b:↓Different lower cases represent statistically significant differences
among time periods for each group (Wilcoxon test, p < 0.05)
canals were instrumented in a crown-down manner using
PTUR instruments to prevent apical extrusion of debris by
instrumentation. [31]. Irrigation was conducted very carefully
using side-vented needles. It is important to note that, despite
careful fulfillment of endodontic treatment, there is always the
possibility of mechanical/chemical injury to the periapical tissue [32]. Furthermore, the most promising organic solvent
used for gutta-percha dissolving is eucalyptol, if the balance
of the toxicity and effectiveness is considered [16, 33].
Therefore, in this study, a 100% eucalyptol-based solvent,
Guttasolv, which is commonly used without causing harmful
effects, was preferred.
Previous studies have shown that postoperative pain is apparent during the first 2 days after root canal treatment and
decreases over time [34–36]. Similarly, in our study, the pain
scores for both the groups were the highest on the first day and
showed a daily decrease towards the third day. Within group
evaluations showed that the postoperative pain intensity of
both groups was statistically similar on the first and second
days, whereas it was significantly lower than those days on the
third day. This statistical difference can be attributed to the fact
that the pain, which tends to decrease spontaneously with
time, is markedly reduced for both groups in the third day.
Since pain measurement relies on patient expressions,
using an easy-to-understand pain scale and questionnaire is
critical for a precise pain evaluation. In this study, an NRS
was used, which is reported to be a valid and reliable scale
to measure pain intensity. The strength of this measure over
the VAS is the convenience of administration, in both verbal
and written forms, as well as the simplicity of scoring [37].
Ibuprofen is the most frequently used non-steroidal anti-inflammatory drug for control of pain associated with root canal
treatment because of its safety and efficacy [38, 39]. Therefore, in
this study, ibuprofen was prescribed to patients to be used if
required. No statistically significant difference was found between the two groups in this study in terms of analgesic intake.
In the field of endodontics, a flare-up refers to the severe
pain and/or swelling after root canal treatment procedures. In
this study, no swelling was observed in any of the cases. Since
NRS scores of 8, 9, and 10 represent severe pain, they were
evaluated as flare-ups. The overall prevalence of flare-ups in
this study was 12.5%. In terms of flare-up rates, the nonsolvent (13.5%) and solvent (11.1%) groups were statistically
similar. These values are consistent with previously reported
endodontic flare-up values of 1.4 to 16% [27, 28, 40]. These
values are close to the upper limit of previously reported percentages. These high percentages may be due to the existence
of more resistant infections in retreatment cases, which is suggested to be a contributing factor for postoperative complications [41, 42]. Moreover, the presence of the periapical lesions
that has been reported to be a risk-enhancing factor for the
development of postoperative pain may have elevated our
flare-up percentages [43].
Age, sex, and tooth localization are suggested to play role
in postoperative pain [44–47]. In agreement with some other
studies [40, 48, 49], none of these baseline characteristics
showed a significant effect on postoperative pain intensity in
the current study. Furthermore, statistical analysis of the baseline clinical features (age, sex, tooth localization) revealed no
significant difference between the two groups, thus showing
an appropriate randomization, which minimizes the effect of
these variables.
Previous studies have shown a higher incidence of postoperative pain in cases with associated preoperative pain [42, 47,
50]. To eliminate the effect of this variable, in this study, only
the painless cases were included.
This study has some inevitable limitations because of
in vivo conditions. Since each tooth has its own specific dimensions, the final apical preparation sizes could not be standardized. This may have affected the amount of apically extruded debris. Besides, endodontic retreatment involves a
multistep, complex process chain, and each step has the potential to cause pain. Lastly, the different pain thresholds of the
participants may have affected the pain scores.
The strength of the current study lies in its design. The
study was designed as a randomized controlled trial, which
is accepted to be an integral part of evidence-based medicine.
The guidelines of consolidated standards of reporting trials
(CONSORT) statement [51] was followed for transparent
and accurate reporting. To prevent bias, blinding and randomization were performed. The researcher collecting the outcome data, and the statistician and patients were blinded to
the groups. Only the researcher performing the clinical procedures was not blinded and was aware of the allocated intervention immediately before the root canal filling removal (allocation concealment).
Conclusion
Within the study limitations, the use of a gutta-percha solvent
during the removal of root canal filling did not result in a
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significant reduction in postoperative pain. However, it should
be considered that treatment outcome studies are required to
determine the necessity or efficacy of this or any technique.
Acknowledgments The authors gratefully acknowledge Prof. Dr. Sıddık
Keskin for performing the statistical analysis.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Ethical approval All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later
amendments or comparable ethical standards.
Informed consent Informed consent was obtained from each of the
participants included in the study.
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