UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2024.e4198
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Braz Dent Sci 2024 Apr/June;27 (2): e4198
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Evaluation of different methods of calcium hydroxide removal from
root canals with simulated internal resorptions
Avaliação de diferentes métodos de remoção de hidróxido de cálcio de canais radiculares com reabsorções internas
simuladas
Hermano Camelo PAIVA1 , Amanda Mourão Ley BARROS2 , George Táccio de Miranda CANDEIRO2,3 , Luiza Riomar PAZ1 ,
Elaine Faga IGLECIAS1 , Laila Gonzales Freire GUSUKUMA1 , Giulio GAVINI1
1 - Universidade de São Paulo, Faculdade de Odontologia, Departamento de Dentística. São Paulo, SP, Brazil.
2 - Universidade Federal do Ceará, Departamento de Odontologia Restauradora. Fortaleza, CE, Brazil.
3 - Centro Universitário Christus, Programa de Pós-graduação em Ciências Odontológicas, Forlateza, CE,Brazil.
How to cite: Paiva HC, Barros AML, Candeiro GTM, Paz LR, Iglecias EF, Gusukuma LGF, et al. Evaluation of different
methods of calcium hydroxide removal from root canals with simulated internal resorptions. Braz Dent Sci. 2024;27(2):e4198.
https://doi.org/10.4322/bds.2024.e4198
ABSTRACT
Objective: This study evaluated different methods of calcium hydroxide (CH) removal from root canals with
simulated internal resorptions using microcomputed tomography (micro-CT). Material and Methods: Sixty
acrylic resin blocks with simulated root canals and internal resorptions were prepared using a Reciproc R25 le
and then lled with CH. The blocks were divided into ve test groups (n=12) according to the method used
for CH removal: hand les (HF), Easy Clean (EC), passive ultrasonic irrigation (PUI), XP-Endo Finisher (XP),
XP-Endo Finisher + PUI (XP+PUI). The blocks were scanned using a SkyScan 1172 scanner before and after
CH removal to measure the volume and percentage of CH removal. The OriginPro 2017 software was used for
statistical analyses. The level of signicance was set at p<0.05 for all tests. Results: No method under study
removed all CH. All methods had similar results in the cervical third (P>0.05). The percentage of CH removal
was signicantly greater in the area of internal resorption and along the total length of the canal in the XP+PUI
group (P<0.05). The best results of CH removal were found in the apical third of roots in the XP+PUI and PUI
groups (P>0.05). Conclusion: No method removed all CH from the root canals, but the combined XP+PUI
method removed more CH than the other methods, especially from the area of the internal resorption.
KEYWORDS
Calcium hydroxide; Dental instruments; Dental pulp cavity; Root resorption; X-ray microtomography
RESUMO
Objetivo: Este estudo avaliou diferentes métodos de remoção de hidróxido de cálcio (CH) de canais radiculares com
reabsorções internas simuladas por meio de microtomograa computadorizada (micro-CT). Material e Métodos:
Sessenta blocos de resina acrílica com canais radiculares simulados e reabsorções internas foram preparados
com lima Reciproc R25 e posteriormente preenchidos com CH. Os blocos foram divididos em cinco grupos de
teste (n=12) de acordo com o método utilizado para remoção de CH: limas manuais (HF), Easy Clean (EC),
irrigação ultrassônica passiva (PUI), XP-Endo Finisher (XP), XP -Endo Finalizador + PUI (XP + PUI). Os blocos
foram escaneados usando um scanner SkyScan 1172 antes e depois da remoção do CH para medir o volume e
a porcentagem de remoção do CH. O software OriginPro 2017 foi utilizado para análises estatísticas. O nível de
signicância foi estabelecido em p<0,05 para todos os testes. Resultados: Nenhum método em estudo removeu
todos o CH. Todos os métodos tiveram resultados semelhantes no terço cervical (P>0,05). A porcentagem de
remoção de CH foi signicativamente maior na área de reabsorção interna e ao longo do comprimento total do
canal no grupo XP+PUI (P<0,05). Os melhores resultados de remoção de CH foram encontrados no terço apical
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Braz Dent Sci 2024 Apr/June;27 (2): e4198
Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
INTRODUCTION
Root resorptions, which may be classied as
internal or external, are caused by the progressive
reabsorption of hard dental tissue due to the
action of osteoclasts [1]. Teeth with an internal
root resorption should undergo endodontic
treatment and total removal of inammation [1].
The endodontic treatment of teeth with an
internal root resorption poses some difculty for
endodontists, as resorption defects are difcult to
access. Because of the limitations of endodontic
les to treat these cases, intracanal medicaments
have to be used, and calcium hydroxide (CH) is
the most frequently used to promote disinfection,
necrotize residual tissue and stop bleeding [2-5].
CH should be completely removed from
the canal before obturation. If any of it remains
inside a root canal, it may affect the penetration
of the obturating cements into the dentinal
tubules [6], reduce adherence to dentin and
negatively affect the sealing capacity of obturating
materials [7]. In addition, it may react chemically
with these other materials and affect their
physical properties [8]. The most frequent
method to remove CH is the use of a hand le of
a size compatible with that of the master apical
file used for cleaning and shaping, together
with abundant irrigation [9,10], however, other
devices and techniques can be used to improve
the reach of chemical substances, which can be
used to remove CH from root canals.
Passive ultrasonic irrigation (PUI), which
consists of the agitation of an irrigant using an
ultrasonic insert inside the root canal, is used
for the same purpose and has been widely
studied [11]. EasyClean (Easy Equipamentos
Odontológicos, Belo Horizonte, Brazil), a
very exible #25.04 le made of acrylonitrile
butadiene styrene, produces vigorous intracanal
uid agitation [12,13]. XP-Endo Finisher (FKG
Dentaire, La Chaux-de-Fonds, Switzerland)
is a file with an asymmetric structure, which
increases the efcacy of cleaning and shaping
and the removal of debris and biolm. This le
has a small core (# 25/00), and its exclusive
NiTi alloy (MaxWire® - Martensite-Austenite
Electropolish-eX) grants the le good exibility
and the capacity to expand sideways. Because
of this expansion, the le may touch and clean
concave and deeper areas of the dentin walls,
thus preserving the original anatomic shape of
the internal root canal. The mechanical activity of
this le, combined with irrigant agitation, seems
to increase the efciency of cleaning the main
canal and the dentinal tubules [14] with less
debris, similarly to PUI [15]. However, no study
has evaluated the combined use of PUI and XP
as an additional irrigation protocol to remove CH
from internal resorptions of root canals.
Most studies that evaluated CH removal
from root canals with internal resorptions used
split-tooth models and image analysis [16-20].
However, these study models provide only
two-dimensional analyses, do not measure the
amount of HC remaining in the resorption cavity
accurately and cannot be used for an accurate
standardization of the samples [16-20].
Micro-computed tomography (micro-CT)
is a non-destructive study method that may be
used for a three-dimensional analysis of the
samples, providing accurate information about
sample volume, area and surface [21]. This study
evaluated the removal of CH from root canals
with simulated internal resorptions and compared
different methods of removal. The null hypothesis
was that the irrigant solution activation would not
affect the removal of CH from root canals with
simulated internal resorptions.
MATERIAL AND METHODS
Root canal model and sample preparation
Sixty acrylic resin blocks (IM do Brasil,
São Paulo, Brazil) with simulated canals and an
internal resorption were prepared for this study.
The simulated canals had a #30 apical diameter,
.08 taper and an oval-shaped resorption in the
middle third measuring 5 mm in diameter.
das raízes nos grupos XP+PUI e PUI (P>0,05). Conclusão: Nenhum método removeu todo o CH dos canais
radiculares, mas o método combinado XP+PUI removeu signicativamente mais CH do que os outros métodos,
especialmente da área de reabsorção interna.
PALAVRAS-CHAVE
Hidróxido de cálcio; Instrumentos dentais; Cavidade pulpar dentária; Reabsorção radicular; Microtomograa
de raios X
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Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
Sample size, calculated using the GraphPad
Prism software, was based on data of a pilot
study. A bilateral test for associated samples, at
a level of signicance of 0.05% and test power
of 0.85, indicated a size of 60 samples.
All procedures were carried out by an
endodontic specialist with more than 7 years
of clinical experience. Working length was
determined using #10 hand K-les (Dentsply
Maillefer, Ballaigues, Switzerland) until the
tip was visualized at the apical foramen. Real
working length (WL) was set at 1mm short of
the apical foramen. The foramina of simulated
canals were sealed with a cyanoacrylate adhesive
(Superbonder, Henkel, Düsseldorf, Germany) e
lled with a CH intracanal medicament (Ultracal;
Ultradent, South Jordan, UT) delivered using
a 30-gauge NaviTip cannula (Ultradent, South
Jordan, UT) to 2 mm short of the working length.
The blocks were kept in sealed containers for
21 days [22] and, after that, scanned using an X-ray
micro-CT scanner (SkyScan 1172; Bruker, Kontich,
Belgium). Immediately after that, the blocks were
divided into five test groups (n=12) according
to the method used for CH removal: hand files
(HF), as a control group; Easy Clean (EC); passive
ultrasonic irrigation (PUI); XP-Endo Finisher (XP);
and XP-Endo Finisher and PUI (XP+PUI).
Calcium hydroxide removal
The simulated canals were covered with
opaque tape, and the Reciproc R25 le (VDW,
GmbH, Munich, Germany) was rst used to RWL
in all groups to start removing CH. The irrigants
were inserted into all canals using a 5-mL syringe
(UltraDent, Salt Lake City, UT) and a 27-g
needle (Endo-Eze; UltraDent, Salt Lake City, UT)
inserted to 3 mm short of RWL using back and
forth movements.
All procedures were conducted using
irrigants warmed to 37 °C in a warmer (Qtamp80,
Quanta, Ciudad del Este, Paraguay) containing
distilled water at 37 °C. Water temperature in the
warmer was checked every ve minutes using an
infrared thermometer (HM-88C, HighMed, São
Paulo, Brazil).
The activation time and volume of irrigants
used were based on the study by Freire et al. [23].
Activation protocols are described below:
HF: the canals were rst irrigated with 2 mL
of 2.5% NaOCl (Fórmula & Ação, São Paulo,
Brazil). After that, a #25 K-file was inserted
into the root canal and agitated for 30 seconds.
The root canal was then irrigated with 2 mL
of 17% EDTA and maintained in the canal for
3 minutes (Fórmula & Ação, São Paulo, Brazil),
and the #25 K-le was inserted in the root canal
again and agitated for another 30 seconds.
Finally, the canals were irrigated with 10 mL of
2.5% NaOCl.
EC: after initial irrigation with 2 mL of
2.5% NaOCl, the EC file, powered by a VDW
Silver motor (VDW, Munich, Germany) set at
RECIPROC ALL, was moved in reciprocating
movements for 30 seconds. After that, the canals
were irrigated with 2 mL of 17% EDTA and
maintained in the canal for 3 minutes, after that
EC was used again for 30 seconds. Finally, 10 mL
of 2.5% NaOCl were used for the nal irrigation.
PUI: the canals were first irrigated with
2 mL of 2.5% NaOCl. After that, an ultrasonic
insert (Irrisonic, Helse Corp., Santa Rosa do
Viterbo, Brazil) coupled to an ultrasound device
(Suprasson P5; Satelec Acteongroup, Merignac,
France) at 20% power was inserted in the root
canal to RWL and kept there for 30 seconds. After
that, the canals were irrigated with 2 mL of 17%
EDTA for three minutes and maintained in the
canal for 3 minutes, after that the ultrasonic insert
was activated for another 30 seconds. Finally, the
canals were irrigated with 10 mL of 2.5% NaOCl.
XP: rst, 2 mL of 2.5% NaOCl was placed
into the root canals. The XP-Endo Finisher was
used according to the manufacturer’s instructions
at 800 rpm, with in and out movements up to
RWL, for 30 seconds. After that, the canals were
irrigated with 2 mL of 17% EDTA and maintained
in the canal for 3 minutes, and the XP-Endo
Finisher was activated again for 30 seconds.
Finally, the canals were irrigated with 10 mL of
2.5% NaOCl. Each XP le was used in only three
canals.
XP+PUI: rst, the canals were irrigated with
2 mL of 2.5% NaOCl while XP was activated
according to the manufacturer’s instructions at
800 rpm and within and out movements up to
RWL for 30 seconds. Immediately after that, 2 mL
of 17% EDTA was placed into the root canals
and maintained in the canal for 3 minutes, and
the ultrasonic Irrisonic insert was activated for
30 seconds, as previously described. Finally, the
canals were irrigated with 10 mL of 2.5% NaOCl.
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Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
After the application of the CH removal
protocols, the blocks were scanned again using
micro-CT.
Microcomputed tomography
A SkyScan 1172 scanner was used for the
acquisition of micro-CT images at 90 kV, 278 mA,
360° rotation, 0.5° rotation stepsize, and voxel
size of 17.42 mm. The 1-mm-thick lter used was
made of copper.
The 700 2D images acquired for each
specimen were stored in TIFF les and saved in
an external HD.
The NRecon 1.6.10.4 software reconstructed
the 2D images at different angles using a
modied Feldkamp cone-beam reconstruction
algorithm implemented on a computer cluster.
Reconstruction parameters were adjusted for
noise suppression using the following fine-
tuning function: Gaussian smoothing filter
(kernel = 2), beam hardening correction of
40%, post-alignment of 0.50 to compensate
possible misalignment during acquisition, and
ring artifacts correction of 10.
Image Analysis
DataViewer 1.5.1 (Bruker-microCT) was
used to record 3D image data acquired before and
after labeling in software packages of the x, y and
z axes. CTan 1.16.4.1 and CTvol 2.3.2.0 (Bruker-
microCT) were used to create and visualize 3D
models and to measure CH volume. The gray
scale necessary to recognize each object in the
study was determined using a density histogram
and a global thresholding method. Original
and segmented scans were compared to ensure
segmentation accuracy. A customized processing
tool and task lists based on arithmetic and logical
operations were used to create binary images
of CH. The volume of CH that was removed
was calculated by subtracting CH volume after
use of the devices from initial total CH volume.
The percentage of CH removed was calculated
using the following formula:
(remaining CH volume x 100)/(total CH volume)
Statistical analysis
The Origin Pro 2017 software was used for
statistical analyses, and the level of signicance
was set at p<0.05. Parametric ANOVA was used
for the analysis of volume of CH removal because
of variance homogeneity and data normality.
RESULTS
No method under study removed CH from
inside the root canals completely. Regardless of
method, the cervical third had better removal
percentages than the other thirds, with a
statistically significant difference in the HF,
EC and XP groups (P<0.05). In the P and
XP+PUI groups, CH removal in the cervical
third was similar to that found in the apical third
(P>0.05). In the cervical third, mean variation
of CH removal was 95.2% and 99.9%, with no
statistically signicant difference between groups
(P>0.05). In the apical third, mean variation
of CH removal between groups ranged from
57.3% to 92.4% (P<0.05), and the PUI and
XP+PUI groups had the lowest percentages of
remaining CH (P>0.05). Table I shows the mean
percentages of CH removal in the groups.
The removal from oval-shaped resorptions
was signicantly better in XP+PUI than in the
other groups (P<0.05).
In general, the percentage of total CH
removal along the whole canal was signicantly
greater in XP+PUI (p<0.05) than in the other
groups (Figure 1). Figure 2 shows the 3D models
of the different activation groups before and after
CH removal from the simulated canals.
DISCUSSION
This study compared the effectiveness of
different CH removal methods – HF, EC, XP and
XP + PUI - from simulated canals with internal
resorptions. The combined use of XP+PUI was
signicantly more effective in removing CH form
the apical third, the oval-shaped area of the
resorption and the whole of the canals, and the
null hypothesis was, thus, rejected.
Intracanal medicaments containing CH
have been indicated in cases of internal root
resorption [2]. The CH was manteined inside
the simulated root canals per 21 days, as the
average time to reach maximum pH can vary
from 8 to 24 days for the use of CH with aqueous
vehicles [22]. However, such medicaments
have to be completely removed from the root
canal before obturation, because remaining
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Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
CH may negatively affect the quality of the
obturation [5-7]. No method used in this study
removed CH completely from inside the root
canal, particularly from the oval-shaped area of
the resorption, which conrms ndings of other
studies [11,17,18,20,24-27].
The HF, EC, PUI and XP groups had similar
results in the cervical third and in the oval-
shaped area of resorptions. XP+PUI had results
similar to those of PUI alone in the cervical and
apical thirds, but results of CH removal from the
oval-shaped area of resorptions and the whole
Table I - Mean (± standard deviation) percentage of calcium hydroxide removed from simulated canals with internal resorptions after use of different
irrigation methods: HF – hand file, EC –EasyClean, PUI – passive ultrasonic irrigation, XP – XP-Endo Finisher, XP+PUI – combined XP and PUI
Cervical Third Apical Third Oval-shaped area Total
Mean (%) Standard
deviation Mean Standard
deviation Mean (%) Standard
deviation Mean (%) Standard
deviation
HF 95.2Aa 10.4 57.9Bb 25.5 11.2Cb 15.4 22.7b13.0
PUI 99.7Aa 0.5 89.2Aac 10.2 13.9Bb 8.5 27.6b9.1
XP 97.3Aa 8.2 67.6Bbc 19.7 14.1Cb 8.8 25.8b10.5
EC 95.3Aa 4.9 57.3Bb 20.1 5.7Cb 3.9 18.8b4.9
XP+PUI 99.9Aa 0.3 92.4Aa 17.2 30.2Ba 8.6 58.4a12.1
Different uppercase letters indicate statistically significant differences (P<0.05) in the comparison between thirds when the same CH removal
method was used. Different lowercase letters indicate statistically significant differences (P<0.05) in the comparisons of the same canal third
between groups.
Figure 1 - Mean percentage of calcium hydroxide removal from simulated canals with internal resorptions after the use of different irrigation
methods: HF – hand file, EC –EasyClean, PUI – passive ultrasonic irrigation, XP – XP-Endo Finisher, XP + PUI – combined XP and PUI. Different
lowercase letters indicate statistically significant differences (P<0.05) in the comparisons of the same canal third between groups.
Figure 2 - 3D models of different activation methods before and after CH removal from simulated canals.
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Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
of the canal were not significantly greater.
The combination of the XP file and PUI had
signicantly better results than those of the other
groups. Denna et al. [19] found similar results in
a recent study, but they studied only canals with
no morphological changes.
A possible explanation for this result may
be associated with the mechanical action of
the XP le and its capacity to expand sideways
to a diameter of up to 6 mm, increasing its
area of contact with the dentin walls [28].
As it touches the root canal walls, the XP le
displaces CH from the oval-shaped area of
resorptions and from other difficult-to-reach
areas. The subsequent supplemental acoustic
streaming and cavitation transmitted by the
ultrasonic insert are responsible for cleaning and
nal removal of the medicament that remained
as a suspension inside the canal.
The HF group was a control group, as this
type of le does not touch canal walls and has
no additional vibration effect [29,30]. The results
in this group did not indicate any advantage in
CH removal from the area of resorption. In some
studies, EC was found to be an alternative for
root canal cleaning after cleaning and shaping.
However, its efficacy was not good enough
to justify its use in CH removal in cases of
internal resorption in this study. The agitation
of the irrigant used with EC did not result in
adequate cleaning of the apical third or the
oval-shaped area of resorption, and results were
similar to those found for HF. Some authors,
however, found that this method removed
debris efcaciously from the apical region and
isthmuses, especially when rotary movements
were used [31]. Maybe the low efficacy of
EC resulted from its use with reciprocating
movements, as this type of movement, although
recommended by manufacturers [11,31], has
had worse results than when EC is used with
rotary movements [31]. No study, however, has
found statistic differences between EC and PUI
in CH removal from oval canals [32], or in debris
removal [31].
Keskin et al. [16] and Arora et al. [26] did
not nd any differences between PUI and XP,
which is in agreement with the ndings in this
study. Marques-da-Silva et al. [18], in contrast,
found that XP removed signicantly more CH than
PUI in extracted teeth with simulated cavities.
In canals with no morphological anomalies, PUI
AND XP were similarly efcacious in removing
CH and debris [19,33]. In this study, the separate
comparison of the parts of the canal with no
anomalies – cervical and apical thirds – did not
reveal any difference between activations using
PUI or XP.
In this study, the volume of remaining
CH was measured using micro-CT. CH volume
before and after the use of different methods of
removal was calculated using the CTan software,
and accurate values were obtained for statistical
analyses. Studies in the literature have evaluated
other CH removal methods in simulated internal
resorptions of extracted teeth that were split
longitudinally [16,18,26]. The main studies used
radiographs and light microscopy [16,18,26,34].
Micro-CT ensured a very accurate measurement
of the volume of CH removed without destroying
the specimen. Moreover, a resin block was used
with a simulated canal and scanned using a 3D
printer, which standardized all the volumes
of the specimens, thus avoiding errors in the
preparation of simulated cavities, as described in
other studies [15,16,35]. Another advantage was
the fact that it was not necessary to use human
teeth, which have great variations [35,36].
This study demonstrated that, in teeth
with internal resorptions, the combination of
complementary techniques to activate irrigants
is extremely important to potentiate the removal
of intracanal medicaments, such as CH. Further
studies should be conducted to improve this
endodontic treatment procedure, which should
result in better root canal sealing.
CONCLUSIONS
The use of XP+PUI was the most efcacious
method in the removal of CH medicaments from
root canals with simulated internal resorptions.
No method in this study removed CH medicaments
completely.
Author’s Contributions
HCP, AMLB: Conceptualization, Methodology,
Formal Analysis, Project Administration. GTMC,
LRP, EFI, LGFG: Conceptualization, Methodology,
Formal Analysis, Project Administration,
Supervision. GG: Formal Analysis, Project
Administration, Supervision.
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Paiva HC et al.
Evaluation of different methods of calcium hydroxide removal from root canals with simulated internal resorptions
Paiva HC et al. Evaluation of different methods of calcium hydroxide removal
from root canals with simulated internal resorptions
Conict of Interest
The authors have stated explicitly that there
are no conicts of interest in connection with
this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
Nothing to declare.
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Hermano Camelo Paiva
(Corresponding address)
Universidade de São Paulo, Faculdade de Odontologia, Departamento de
Odontologia Restauradora, São Paulo, SP, Brazil.
Email: hermanopaiva@usp.br
Date submitted: 2023 Dec 12
Accept submission: 2024 May 06
