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R E S E A R C H A R T I C L E Open Access
Evaluation of antibacterial activity of
propolis on regenerative potential of
necrotic immature permanent teeth in
dogs
M. M. El-Tayeb
1
, A. M. Abu-Seida
2*
, S. H. El Ashry
1
and S. A. El-Hady
3
Abstract
Background: This study evaluated the antibacterial efficiency and ability of propolis to promote regeneration of
immature permanent non-vital dogs’teeth.
Methods: Ninety six immature permanent premolars teeth in 6 mongrel dogs were divided randomly into:
experimental teeth (N= 72) and control teeth (N= 24). Periapical pathosis was induced in all experimental and
positive control teeth. Experimental teeth were classified according to the used intra-canal medication into: group I
(N= 36), propolis paste was used and group II (N = 36), triple antibiotic paste (TAP) was used. Bacteriologic
samplings were collected before and after exposure to intra-canal medicaments. After the disinfection period (3
weeks), revascularization was induced in all experimental teeth. Each group was subdivided according to the root
canal orifice plug into: subgroup A (N= 18), propolis paste was used and subgroup B (N = 18), mineral trioxide
aggregates (MTA) was used. Each subgroup was further subdivided according to the evaluation period into 3
subdivisions (6 teeth each): subdivision 1; after 2 weeks, subdivision 2; after one month and subdivision 3; after 2
months. Positive control group had 12 teeth with induced untreated periapical pathosis. Negative control group
had 12 untouched sound teeth. All teeth were evaluated with radiography and histology. The bacteriologic and
radiographic data were analyzed using repeated measures ANOVA and post-hoc Tukey tests. The histologic data
were analyzed using Kruskal-Wallis test, Mann-Whitney U test with Bonferroni’s adjustment and Chi-square test. The
significance level was set at P≤.05.
Results: There was no significant difference in the antibacterial effectiveness between TAP and propolis groups
(P> .05). In all subdivisions, there was no significant difference between the experimental groups in terms of
increase in root length and dentin thickness, decrease in apical closure, new hard tissue formation, vital tissue
formation inside the pulp canal and apical closure scores (P> .05).
Conclusion: Propolis can be comparable with TAP as a disinfection treatment option in regenerative endodontic.
As a root canal orifice plug after revascularization of necrotic immature permanent teeth in dogs, propolis induces a
progressive increase in root length and dentin thickness and a decrease in apical diameter similar to those of MTA.
Keywords: Apical closure, Dentin thickness, Propolis, regenerative endodontic, Root length, Triple antibiotic paste
© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
* Correspondence: ashrafsida@cu.edu.eg
2
Department of Surgery, Anesthesiology & Radiology, Faculty of Veterinary
Medicine, Cairo University, Giza Square, Giza PO: 12211, Egypt
Full list of author information is available at the end of the article
El-Tayeb et al. BMC Oral Health (2019) 19:174
https://doi.org/10.1186/s12903-019-0835-0
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Background
Propolis is a natural substance, containing about 55%
resinous compounds and balsam, 30% beeswax, 10%
ethereal and aromatic oils, and 5% bee pollen. This com-
position depends upon the type of plants available to the
bees. Therefore, propolis changes in odor, color and
probably therapeutic properties according to the season
and source [1].
Due to the diversity of its therapeutic and biological
properties, several recent studies have been carried out
on propolis medical and dental applications [2,3]. In
dentistry, propolis has been used for the treatment of
periodontitis, root canal disinfection, pulp capping and
as a subsidiary treatment for gingivitis and plaque with-
out any recorded allergic reactions [3,4].
Propolis has antimicrobial and anti-inflammatory
properties, so it could be applied as an effective intra-
canal irrigant and intra-canal medicament [5–7]. Previ-
ous in vitro studies concluded that propolis has a good
antibacterial activity against E. faecalis in the root canals,
suggesting that it may be used as an alternative intra-
canal medicament [6].
Successful endodontic therapy is based primary upon
removal of as many bacteria as possible from the root
canal and creation of unsuitable environment for the
remaining microorganisms. In this regard, several intra-
canal medicaments have been applied but no single
agent has been found to be completely effective. There-
fore, topical application of TAP consisting of a mixture
of ciprofloxacin, metronidazole and minocycline or
doxycycline is commonly used for sterilization of in-
fected root canal [8]. Due to the disadvantages of TAP,
search for an ideal new intra-canal antimicrobial is con-
tinuing. Therefore, propolis, as a natural product with
useful biological activities and no reported complica-
tions, was selected in the present study.
Recently, regenerative endodontic treatment is advised
for treatment of non-vital immature permanent teeth
[9–11]. Revascularization of the necrotic dental pulp is
the most commonly applied regenerative endodontic
treatment [12,13].
The hypothesis of this study was that propolis may
play a role in the regenerative endodontic due to its anti-
microbial, anti-inflammatory, analgesic, antioxidant, and
immune stimulant activities. Therefore, this study evalu-
ated the antibacterial efficiency of propolis and its ability
to promote the regeneration as a root canal orifice plug
after revascularization of immature non-vital dogs’teeth.
Methods
Animals
The present study was approved by the Institutional
Animal Care and Use Committee at Faculty of Dentistry,
Ain Shams University, Egypt (No: FDASU-REC-16-
2012). The authors followed up all institutional and
international guidelines for animal care and use during
this study. The Animal Research: Reporting in Vivo Ex-
periments guidelines (ARRIVE) were also followed up.
Four premolars were used in each quadrant of six appar-
ently healthy immature mongrel stray dogs. These ani-
mals were obtained commercially from Al-Fahad
Trading Company for Animals (Abu-Rawash, Giza,
Egypt). The animals were of both sexes and their weight
and age ranged between 10 and 15 kg (mean12.5 ± 0.5)
and 6–9 months (mean 7.5 ± 0.5), respectively. Each dog
was subjected to a full physical examination by an expert
veterinarian to exclude any diseased dog. The animals
were kept in the animal house at Faculty of Veterinary
Medicine, Cairo University under proper conditions of
nutrition, ventilation, clean environment and 12 h light/
dark cycle. They were kept on separate kennels (1.5 m ×
2.5 m × 3 m) and acclimatized to housing and diet for
two weeks before the experiment. The dogs were given
two meals per day (Soft food and milk) and fresh water
ad libitum.
Classification of samples
The samples (96 teeth) were divided using simple
randomization into: experimental teeth (N= 72) and
control teeth (N= 24). The experimental teeth were clas-
sified according to the used intra-canal medications into:
group I (N= 36 teeth); the root canals were medicated
with pure propolis paste and group II (N = 36 teeth); the
root canals were medicated with TAP.
Each group was subdivided according to the used re-
generative material into: subgroup (A); the root canal
orifice was plugged with propolis paste (N= 18 teeth)
and subgroup (B); the root canal orifice was plugged
with MTA (N = 18 teeth). All experimental and control
groups and subgroups were represented in each dog.
The first mandibular premolars in each dog were used
as positive control and the fourth maxillary premolars
were used as negative control. The other three premo-
lars in each quadrant represented randomly one experi-
mental subgroup.
Each subgroup was further subdivided according to
the evaluation period into 3 subdivisions (6 teeth each):
subdivision (1); after 2 weeks, subdivision (2); after one
month and subdivision (3); after 2 months.
The control teeth (N= 24 teeth) were classified into:
positive control group which represented 12 teeth with
induced periapical infections without any treatment mo-
dalities and negative control group which represented 12
sound teeth left untouched for normal maturation.
Induction of infection
General anesthesia was administrated after fasting the
dogs for 12 h. All dogs were pre-medicated with
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subcutaneous injection of Atropine sulphate (Atropine
sulphate®, ADWIA Co., Egypt), 0.05 mg/kg weight and
Xylazine HCl (Xylaject 2%® ADWIA Co., Egypt), 1.1 mg/
kg body weight given intravenously. The anesthesia was
induced with Ketamine HCl (Keiran®, EIMC Pharmacuti-
cals Co., Egypt) at a dose of 5 mg/kg body weight via a
20-gauge IV cannula fixed in the cephalic vein.
Anesthesia was maintained by 25 mg/kg incremental
doses of Thiopental sodium 2.5% solution (Thiopental
sodium®, EIPICO, Egypt). Radiographic examination was
performed for all teeth to confirm incomplete root for-
mation and to establish a base line working length for
further comparison.
Endodontic access cavity was performed using size #2
diamond stone in all experimental and positive control
teeth to exposing the pulp chamber. A sterile file size
#40 was used to disrupt the pulp tissue. Supra gingival
plaque from the dog’s teeth was mixed with sterile saline
solution; sterile sponge was soaked in the plaque suspen-
sion and then inserted into the pulp chamber. Dogs were
monitored radiographically after four weeks for evidence
of development of periapical pathosis. Dogs were fed soft
diet and given Carprofen (Rimadyl tab®, Pfizer Co., USA)
daily at a dose of 4.4 mg/kg body weight as a pain killer
during this period. The dogs were monitored daily for
pain.
Treatment modalities
Phase I: antibacterial effectiveness
Under the same general anesthetic regimen, complete
aseptic conditions and cotton roll isolation, the previ-
ously infected experimental teeth were re-entered. The
soaked cotton was removed and each root canal was
filled with sterile saline solution as a transport fluid. A
sterile paper point #30 was placed in the root canal as
close to the working length as possible, allowed to satur-
ate, and transferred into tubes containing one mL of
0.9% sterile saline solution. Before placing the paper
point into the tubes, the mouth of each tube was heated
on the flame to prevent contamination.
Each sample was carefully homogenized by being vor-
texed for 30s. Serial 10-fold dilutions (1:10, 1:100 and 1:
1000) were done in saline solution. Then 0.1 mL from each
dilution was smeared to be inoculated on surface of the
plate media (BHI agar plates), incubated at 37 °C for 48 h,
and colony-forming units (CFU) per 1 mL were enumer-
ated. After 48 h, Petri-dishes were examined for bacterial
growth (base line). Each plate was divided into 4 quadrants
and dotted colonies were marked by a marker pen.
According to the group, either propolis paste or TAP
paste was applied as intra-canal medicament.
For preparation of intra-canal propolis paste, Egyptian
propolis was collected from El Monofia province. Three-
hundred grams of frozen propolis were ground and
dissolved in 300 mL of ethanol 96% at 37 °C to obtain
100% (w/v) extract. The mixture was poured into a bot-
tle and incubated for 2 weeks at 30 °C. After incubation,
the supernatant mixture was filtered twice with What-
man no. 4 and 1 filter paper. The filtered mixture was
concentrated at 30 °C for 6 h (1500 rpm). The final ex-
traction of propolis obtained a density of 150 mg/mL.
Glycerin drops (3–4 drops) were added to 150 mg of the
final extract of propolis until a creamy paste was ob-
tained. For preparation of propolis orifice plug, the same
steps were applied but the final extract of propolis (150
mg) was manipulated with 1–2 drops of glycerin until a
thick paste, applicable for orifice plugging, was obtained.
Triple Antibiotic Paste consisting of Metronidazole
500 mg tablet, Ciprofloxacin 250 mg tablet and Doxycyc-
line 100 mg capsule was prepared according Tawfik et al.
[14]. Briefly, the Doxycycline capsule content, a tablet of
Metronidazole and a tablet of Ciprofloxacin were
crushed and ground into homogenous powder in a ster-
ile mortar using a pestle. Saline drops (6–8 drops) were
added and mixed until a creamy paste was obtained. In-
jection of 1–1.5 mL of the prepared pastes into each
canal was carried out to fill the canals using a lentulo
spiral. The access cavity was sealed using sterile cotton
pellet and temporary restoration, Coltosol® F (Coltene
Whaledent, Switzerland). Samples were left for 3 weeks.
Under the same aseptic conditions and anesthesia, the
temporary restoration, cotton pellet, and the paste were re-
moved by copious irrigation with 10 mL sterile saline solu-
tion. The root canals were dried with sterile paper points.
Then post exposure to intra-canal medicaments bacterio-
logic sampling was performed by the previously described
method. After bacteriologic sampling, the root canals were
re-irrigated using 10 mL of NaOCl 2.25% solution then 10
mL of sterile saline solution. The root canals were dried
with sterile paper points for regeneration protocol.
For bacterial count, visible colonies produced before
and after intra-canal medicaments were counted in every
plate. The number of colonies/plate was multiplied by
the corresponding dilution factor and by 10 to deter-
mine the total colony forming units (CFU) per mL of
sample. Antibacterial effectiveness of the different intra-
canal medicaments was assessed by determining the per-
centage of reduction in colony counts (%RCC) before
and after application of the intra-canal medicaments.
The percentage of change was calculated as:
CFU Base lineðÞCFU 3 weeksðÞ
CFU Base lineðÞ 100
Phase II: regeneration protocols
A sterile hand file size # 30 was inserted past to the ca-
nals terminus for induction of bleeding that filled the
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canal space just below the CEJ. After clotting of the
blood, the experimental teeth were divided randomly
and either propolis (subgroup A) or MTA (subgroup B)
orifice plug was used to seal the canal orifice. The plugs
were covered by a moist cotton pellet and the access
cavity was closed with glass ionomer filling (Medifill®,
Promedica, Germany).
Radiographic evaluation
Periapical radiographs were taken after 4 weeks of induc-
tion of periapical pathosis and at 2, 4 and 8 weeks after
revascularization to verify healing of the periapical
pathosis. TurboReg plug-in (TurboReg®, Biomedical Im-
aging Group, Swiss Federal Institute of Technology, Lau-
sanne VD, Switzerland) was used to transform the non-
standardized pre-operative and post-operative radio-
graphs to standardized images. Both increase in root
length and thickness and decrease in apical diameter
were evaluated according to Tawfik et al. [14].
Histopathologic evaluation
According to the post-treatment evaluation period, the
animals were sacrificed by overdose of Thiopental so-
dium (20 mL of 5% solution given intravenously at once).
The teeth and surrounding bone were fixed, prepared
and stained with hematoxylin and eosin for histopatho-
logic assessment. Quantitative histologic evaluation was
performed according to Tawfik et al. [14]. This evalu-
ation included; presence or absence of both new hard
tissue on internal dentinal walls and vital tissues inside
the pulp canal as well as apical closure.
Qualitative histologic analysis was carried out. Histo-
logic findings of hard structure included; dentin (pres-
ence of dentinal tubules), cementum (adherence to
dentin and presence of cementocyte-like cells), bone
(presence of Haversian canals with uniformly distributed
osteocyte-like cells) and periodontal ligament (bridging
of Sharpey’s fibers between cementum and bone).
Statistical analysis
IBM (IBM®, NY, USA) SPSS® Statistics Version 20 for
Windows (SPSS, Inc., IBM Company, USA) was applied
for statistical analysis. Numerical data were presented as
mean and standard deviation (SD) values. Data were
explored for normality using Kolmogorov-Smirnov and
Shapiro-Wilk tests. A logarithmic transformation (Log
10
transformation) of each CFU count was performed be-
cause of the high range of bacterial counts. Histological
scores were tested as non-parametric data while radio-
graphic data showed parametric distribution.
As regards Log
10
CFU data, % increase in root canal
dentin thickness and % decrease in apical diameter; re-
peated measures ANOVA test was used to compare be-
tween the different groups as well as to compare
between the different subdivisions. Tukey’s post-hoc test
was used for pair-wise comparisons between the groups
when ANOVA test was significant. Kruskal-Wallis test
was applied to compare between histologic scores of the
different groups and the different subdivisions. Mann-
Whitney U test with Bonferroni’s adjustment was used
for pair-wise comparisons between the groups when
Kruskal-Wallis test is significant. Prevalence of apical
closure data was presented as frequencies (n) and per-
centages (%). Chi-square (x
2
) test was performed to
compare between the groups and subdivisions. The sig-
nificance level was set at P≤.05.
Results
Clinically all dogs ate and drank well. No signs of pain
and no allergic reactions were reported in any dog dur-
ing this study.
Phase I (antimicrobial effectiveness)
At the base line and after 3 weeks, positive control group
showed the highest mean log
10
CFU. There was a signifi-
cant increase in mean log
10
CFU of bacterial counts
after 3 weeks in the control positive group (P< .001). As
regards percentage of change in bacterial counts, there
was no significant difference between TAP and propolis
groups (P> .05). Both groups showed a decrease in per-
centage of reduction in log
10
CFU. Negative control
group showed no change with a recorded mean value of
.00 ± .00% (Table 1).
Phase II (regeneration)
Radiographic findings
The experimental groups showed a progressive increase in
root length and dentin thickness and a decrease in apical
Table 1 The mean log
10
, standard deviation (SD) values and results of repeated measures ANOVA and Tukey’s tests for comparison
between log
10
CFU of bacterial counts in all groups at different time periods
Time TAP group Propolis group Positive control Negative control P-
value
Mean log
10
± SD Mean log
10
± SD Mean log
10
± SD Mean log
10
±SD
Base line 3.65
Ab
± 0.33 3.88
Ab
± 0.15 4.00
Aa
± 0.02 0.00
Ac
± 0.00 <.001*
3 weeks 2.63
Bb
± 0.13 2.99
Bb
± 0.09 4.84
Ba
± 0.40 0.00
Ac
± 0.00 <.001*
P-value .015* .002* .003* Not computed
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 4 of 12
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diameter with no significant difference (P>.05) at all
evaluation periods (Tables 2,3and 4and Figs. 1and 2).
Increase in root length
After 2 weeks; there was no significant difference in
terms of increase in root length between all groups
(P= .061).
After 1 month, there was no significant difference in
terms of increase in root length between the experimen-
tal and negative control groups (P> .05).
After 2 months; the negative control samples showed
the highest increase in root length. There was no signifi-
cant difference in terms of increase in root length be-
tween the experimental groups (P> .05). Positive control
samples showed the lowest increase in root length after
one month and 2 months periods.
As regards subdivisions, the two weeks period showed
the lowest increase in root length. There was no signifi-
cant difference between 2 weeks and 1 month periods in
terms of increase in root length (P> .05). The two
months period showed the highest increase in root
length (Table 2).
Increase in dentin thickness
After 2 weeks; there was no significant difference in terms of
increase in dentin thickness between all groups (P= .060).
After 1 month; there was a significant difference in
terms of increase in dentin thickness between the ex-
perimental groups and negative control group and posi-
tive control samples (P< .001). There was no significant
difference between experimental and negative control
groups (P> .05). Positive control samples showed the
lowest increase in dentin thickness.
After 2 months; the negative control samples showed
the highest increase in dentin thickness. There was no
significant difference in terms of increase in dentin
thickness between the experimental groups (P> .05).
The experimental groups showed a significant lower in-
crease in dentin thickness than that of negative control
group (P< .001). Positive control group showed the low-
est increase in dentin thickness.
As regards subdivisions, two weeks period showed the
lowest increase in dentin thickness. There was no signifi-
cant difference between 2 weeks and 1 month periods
(P> .05). The two months period showed the highest in-
crease in dentin thickness compared to that of other
subdivisions (Table 3).
Decrease in apical diameter
After 2 weeks; there was no significant difference in
terms of decrease in apical diameter between the groups
(P= .053).
After 1 month; there was a significant difference in
terms of decrease in apical diameter between the groups
(P< .001). There was no significant difference in terms
of decrease in apical diameter between the experimental
groups and negative control group (P> .05). The lowest
percentage of decease in apical diameter was recorded in
the positive control group.
After 2 months; there was a significant difference in
terms of decrease in apical diameter between the groups
(P< .001). Negative control group showed the highest de-
crease in apical diameter. There was no significant differ-
ence in terms of decrease in apical diameter between the
experimental groups (P> .05). The experimental groups
showed a significant lower decrease in apical diameter
than that of negative control samples (P< .001). Positive
control group showed no change in apical diameter after
one month and two months periods.
Regarding subdivisions, two weeks period showed the
most significant lowest decrease in apical diameter
(P< .001). There was no significant difference in terms
of decrease in apical diameter between 2 weeks and 1
month periods (P> .05). Two months period showed the
highest decrease in apical diameter compared with that
of other subdivisions. There was no decrease in apical
diameter through all subdivisions in positive control
group as shown in Table 4.
Histopathologic findings
Regarding the histopathologic findings, there was no sig-
nificant difference in terms of hard tissue formation,
Table 2 The mean, standard deviation (SD) values and results of repeated measures ANOVA and Tukey’s tests for percentage of
increase in root length of different groups, subgroups and subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive
control
Negative
control
P-
value
Propolis plug MTA plug Propolis plug MTA plug
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
2 W 4.9 ± 1.2 5.4 ± 1.4 5.1 ± 1 5.3 ± 1.3 0.00 ± 0.00 5.7 ± 1.3 .061
1 M 13.9
Aa
± 1.8 14.6
Aa
± 1.5 14
Aa
± 1.6 14
Aa
± 1.6 0.00
Bb
± 0.00 14.8
Aa
± 1.8 <.001*
2 M 16.3
Bb
± 1.3 17.1
Bb
± 1.6 16.5
Bb
± 1.4 16.9
Bb
± 2.3 0.00
Cc
± 0.00 17.7
Aa
± 1.5 <.001*
P-value <.001* <.001* <.001* <.001* Not computed <.001*
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 5 of 12
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vital tissues formation inside the pulp space and apical
closure between the experimental groups at all evalu-
ation periods (P> .05).
Findings of the quantitative analysis
Hard tissue formation scores After 2 weeks, the score
of hard tissue formation showed no significant difference
between the experimental groups (P= .061).
After 1 month, there was no significant difference in
terms of hard tissue formation between the experimental
groups and negative control group (P> .05). Positive
control group showed the lowest hard tissue formation
score (Table 5).
After 2 months, the negative control group showed the
most significant highest hard tissue formation score.
There was no significant difference in terms of hard tis-
sue formation between the experimental groups
(P> .05). The experimental and positive control groups
showed a significant lower hard tissue formation score
than that of negative control group (P< .001). Positive
control group showed the lowest hard tissue formation
score after one month and 2 months.
There was a significant difference in terms of hard tis-
sue formation score between the experimental and nega-
tive control groups through all subdivisions (P< .05).
Pair-wise comparison between the subdivisions re-
vealed no significant difference in terms of hard tissue
formation score between 2 weeks and 1 month periods
(P> .05). Two months subdivision showed a significant
higher hard tissue formation score than that of other
subdivisions (P< .05). Positive control group showed no
significant difference between hard tissue formation
scores at all subdivisions (P= 1.000) as shown in Table 5.
Vital tissues formation inside the pulp space After 2
weeks, there was no significant difference in terms of
vital tissue formation inside the pulp space between all
groups (P= .053).
After 1 month; there was no significant difference in
terms of vital tissue formation inside the pulp space be-
tween the experimental and negative control groups
(P > .001). The experimental and negative control groups
showed a significant higher vital tissue formation inside
the pulp space than that of positive control group
(P > .001).
After 2 months; the negative control group showed the
significant highest vital tissue formation inside the pulp
space. There was no significant difference in terms of
vital tissue formation inside the pulp space between the
experimental groups (P > .05). The experimental groups
showed lower vital tissue formation inside the pulp
space than that of negative control group. Positive con-
trol group showed no vital tissue score after one month
and two months.
Table 3 The mean, standard deviation (SD) values and results of repeated measures ANOVA and Tukey’s tests for percentage of
increase in root canal dentin thickness of different groups, subgroups and subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive
control
Negative
control
P-
value
Propolis plug MTA plug Propolis plug MTA plug
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
2 W 3.87
B
± 0.54 4.60
B
± 0.61 3.95
B
± 0.53 4.72
B
± 0.60 0.00 ± 0.00 5.02
B
± 0.75 .060
1 M 6.20
Ba
± 0.74 7.83
Ba
± 0.86 6.35
Ba
± 1.20 7.06
Ba
± 2.10 0.00
b
± 0.00 8.40
Ba
± 1.12 <.001*
2 M 13.28
Ab
± 0.79 13.92
Ab
± 0.85 13.22
Ab
± 2.41 14.50
Ab
± 1.98 0.00
c
± 0.00 17.62
Aa
± 0.54 <.001*
P-value <.001* <.001* <.001* <.001* Not computed <.001*
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
Table 4 The mean, standard deviation (SD) values and results of repeated measures ANOVA and Tukey’s tests for percentage of
decrease in apical diameter of different groups, subgroups and subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive
control
Negative
control
P-
value
Propolis plug MTA plug Propolis plug MTA plug
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
2 W 3.05
B
± 0.97 3.37
B
± 0.74 3.12
B
± 0.74 3.55
B
± 0.61 0.00 ± 0.00 4.00
B
± 1.15 .053
1 M 6.23
Ba
± 1.48 7.45
Ba
± 1.09 5.24
Ba
± 1.04 7.99
Ba
± 2.12 0.00
b
± 0.00 8.23
Ba
± 1.09 <.001*
2 M 30.50
Ab
± 1.84 31.77
Ab
± 1.04 32.48
Ab
± 4.20 34.00
Ab
± 5.59 0.00
c
± 0.00 46.85
Aa
± 1.03 <.001*
P-value <.001* <.001* <.001* <.001* Not computed <.001*
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 6 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
There was a significant difference in terms of vital tis-
sue formation inside the pulp space between the experi-
mental and negative control groups at all evaluation
periods (P< .05) as shown in Table 6. There was no sig-
nificant difference between 2 weeks and 1 month periods
(P> .05). Two months period showed the most signifi-
cant highest vital tissue formation inside the pulp space
compared with that of 2 weeks and 1 month periods.
There was no significant difference between vital tissue
formation scores at all evaluation periods (P= 1.000) as
shown in Table 6.
Apical closure After 2 weeks; no group showed apical
closure.
After 1 month; there was no significant difference in
terms of apical closure between the groups (P= .172).
After 2 months; there was a significant difference be-
tween the groups (P= .010). Negative control group
showed the highest prevalence of apical closure while
positive control group had no apical closure. Experimen-
tal groups showed a low and equal prevalence of apical
closure.
High prevalence of apical closure was found after 1
month in all experimental and negative groups. Further
increase in prevalence of apical closure was observed
after 2 months. In negative control group, there was a
significant difference in terms of apical closure between
the evaluation periods (P= .002) as shown in (Table 7).
Findings of the qualitative analysis In subgroup A
(propolis), changes within the hard and soft tissues along
the three evaluation periods were observed. Cementum
like tissue was observed along the inner surface of root
dentin resulting in an increase in the root thickness.
Most of the teeth showed closure of the apical terminus
of the root with cementum like tissue. Pulp like fibrous
tissue devoid of odontoblastic layer with calcified islands
of osteoid tissue was seen (Fig. 3).
In subgroup B (MTA), changes within the hard and
soft tissues along the three evaluation periods were ob-
served. Teeth showed formation of cementum like tissue
along the inner aspect of root dentin resulting in an in-
crease in dentin thickness. Some teeth showed a newly
formed layer of dentin along the inner aspect of the root
leading to an increase in the root thickness (Fig. 4). Most
of the teeth showed closure of the apical terminus of the
root with cementum formation; however closure of the
apical terminus with dentin formation was demonstrated
Fig. 1 Representative radiographs of subgroup (A); Propolis over
empty canal. (a): Preoperative radiograph. Postoperative radiographs
two weeks (b), one month (c) and two months (d) after
revascularization protocol
Fig. 2 Representative radiographs of subgroup (B); MTA over empty
canal. (a) Preoperative radiograph. Postoperative radiographs two
weeks (b), one month (c) and two months (d) after
revascularization protocol
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 7 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
in some teeth (Fig. 5). Pulp like fibrous connective tissue
with no odontoblastic layer was seen in most teeth. The
teeth with dentin formation were accompanied with the
presence of pulp like tissue with odontoblastic layer.
Discussion
A complete elimination of necrotic tissues and infection
from the root canal is essential for a successful endodon-
tic therapy [15]. Moreover, treatment of immature nec-
rotic teeth constitutes a great challenge due to weakness
of dentinal walls and difficult apical sealing [16].
In last few years, regenerative endodontic has gained
much attention as an alternative biological treatment of
immature permanent necrotic teeth because it allows
further root maturation [17,18]. Revascularization
through induction of bleeding inside the dental pulp is a
simple technique for regenerative endodontic [12,13].
Due to its ant-inflammatory, antibacterial and biocom-
patibility features, propolis had been studied for several
medical uses. Propolis has been used in dentistry for
treatment of aphthous ulcers, periodontitis, Candida
albicans and root canal disinfection due to its advan-
tages; it does not stain the tooth crown, inhibits the for-
mation of plaque, is preserved in the root canal, and
enhances the bone regeneration [19–22].
Accordingly, the aims of this study were to assess both
antibacterial efficiency of propolis during management
of infected root canal and the ability to promote
regeneration after revascularization for management of
immature non-vital dogs’teeth.
The dog was selected as an experimental animal for
this biological experiment due to his similar apical repair
compared with that of humans but in a short time (aver-
age one sixth of human) due to high growth rate [23].
Moreover, the selected dogs aged 6–9 months which are
suitable for assessment of the immature teeth and with-
standing of general anesthesia [14]. Dogs
,
premolars
were selected for this study due to their suitable-sized
root canals for different endodontic manipulations and
they are easily accessible.
Access cavities were performed in the selected teeth and
left open for four weeks in order to induce periapical in-
fection, for simulation of clinical cases. The periapical
pathosis was confirmed by radiographic examination as
mentioned before [13].
Failure of using rubber dam for isolation was attrib-
uted to the morphology of dogs
,
premolars that makes
fixation of the rubber dam clamp to the tooth difficult.
Therefore, isolation was achieved by atropine injection
to decrease salivation during surgery and cotton rolls.
In our study, no instrumentation was performed
due to thin root dentinal walls of immature teeth.
Similar finding was recorded before [24]. Therefore,
disinfection of immature permanent teeth with nec-
rotic pulp is entirely depended on the chemical action
of intra-canal agents. However this is also another
Table 5 The mean, standard deviation (SD) values and results of Kruskal-Wallis and Mann-Whitney U tests for comparison between
hard tissue formation scores of different groups, subgroups and subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive
control
Negative
control
P-
value
Propolis plug MTA plug Propolis plug MTA plug
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD
2 W 0.50
B
± 0.23 0.67
B
± 0.42 0.60
B
± 0.41 0.63
B
± 0.28 0.00 ± 0.00 0.68
B
± 0.44 .061
1 M 0.67
Ba
± 0.52 0.83
Ba
± 0.41 0.65
Ba
± 0.34 0.77
Ba
± 0.40 0.00
b
± 0.00 1.00
Ba
± 0.00 <.001*
2 M 1.17
Ab
± 0.41 1.50
Ab
± 0.55 1.30
Ab
± 0.60 1.55
Ab
± 0.65 0.00
c
± 0.00 2.0
Aa
± 0.61 <.001*
P-value .040* .037* .042* .038* 1.000 <.001*
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
Table 6 The mean, standard deviation (SD) values and results of Kruskal-Wallis and Mann-Whitney U tests for comparison between
vital tissue formation inside the pulp space of different groups, subgroups and subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive
control
Negative
control
P-
value
Propolis plug MTA plug Propolis plug MTA plug
Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± S D
2 W 0.67
B
± 0.52 0.67
B
± 0.52 0.52
B
± 0.42 0.70
B
± 0.45 0.00 ± 0.00 0.67
B
± 0.52 .053
1 M 1.17
Ba
± 0.75 1.50
Ba
± 0.55 1.22
Ba
± 0.39 1.56
Ba
± 0.69 0.00
b
± 0.00 1.53
Ba
± 0.62 .001*
2 M 1.83
Ab
± 0.41 2.00
Ab
± 0.00 1.95
Ab
± 0.67 2.06
Ab
± 0.70 0.00
c
± 0.00 2.50
Aa
± 0.47 .010*
P-value .002* .003* .035* .016* 1.000 .006*
*: Significant at P≤.05, Different small superscripts in the same row are statistically significantly different. Different capital superscripts in the same column are
statistically significantly different. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 8 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
challenge because these agents may affect the viability
of regeneration cells [25].
In the present study, the antimicrobial agents were
kept inside the dental roots for 3 weeks which is a suffi-
cient time for canal disinfection as mentioned before [8].
Due to the complexity of root canal infection, single
antimicrobial agent is not sufficient for effective disinfec-
tion [26]. Thus mixed antimicrobials are more likely to
use during endodontic therapy. Although triple anti-
biotic paste is one of the most commonly used anti-
microbial combinations in endodontics, it has some
drawbacks such as staining of the teeth [8]. Therefore,
propolis was used in the present study as an alternative
intra-canal medication in revascularization due to its
natural origin and its ability to maintain PDL cell viabil-
ity when used as a storage medium of avulsed teeth [27].
So these were the hypotheses for assessment of the re-
generative potential of propolis in the current study.
In the present study, ethanol extract of propolis was
used because it promotes the regeneration of bone and
hard tissue bridge formation. Additionally, using of a
scaffold is an essential factor for a successful regenera-
tive endodontic because it supports cell proliferation,
Table 7 The frequencies (n), percentages (%) and results of Chi-square test for apical closure in different groups, subgroups and
subdivisions
Time Intra-canal propolis paste Intra-canal TAP paste Positive control Negative
control
P-value
Propolis plug MTA plug Propolis plug MTA plug
N% N% N% N%N % N%
2 W 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 Not computed
1 M 2 33.3 3 50.0 3 50.0 3 50.0 0 0.0 4 66.7 0.172
2 M 4 66.7 4 66.7 4 66.7 4 66.7 0 0.0 6 100.0 0.010*
P-value 0.050* 0.017* 0.048* 0.048* Not computed 0.002*
*: Significant at P≤0.05. TAP: Triple antibiotic paste, MTA: Mineral trioxide aggregates
Fig. 3 (a) Photomicrograph for a sample of subgroup A (propolis)
showing formation of cementum like tissue on the inner aspect of
the root dentin (H&E, X200). (b) Photomicrograph for a sample of
subgroup A showing pulp like tissue with areas of osteoid like tissue
inside the root canal and closure of the apex (H&E, X100)
Fig. 4 (a) Photomicrograph for a sample of subgroup B (MTA) at 2
month showing formation of new layer of dentin like tissue (arrows)
on the inner root wall (H&E, X200). (b) Higher magnification of a
sample of subgroup A (propolis) showing fibrous connective tissue
with islands of cementum like tissue inside the root canal space
(H&E, X200)
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 9 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
organization, differentiation and vascularization. In the
present study, the blood clot was used as a scaffold be-
cause it is an easy, efficient and biological process. On
the other hand, using other natural scaffolds in previous
studies resulted in little success with several drawbacks
[14,17,28].
Regarding the antimicrobial action of both propolis
and TAP, there was no significant difference between
them. The antimicrobial activity of propolis could be at-
tributed to functional and structural damages of the mi-
crobial cell wall, inhibition of bacterial RNA-polymeras
and immunomodulatory, anti-oxidative, and healing ef-
fects [19,22].
Both radiographic and histologic examinations are ne-
cessary for assessment of healing of immature necrotic
teeth [12–14]. The present radiographic findings were
generally consistent with the histologic findings. These
findings are in agreement with those reported before [9,
12,14,29]. However, Wang et al. [11] concluded that
radiographic findings were not accurate regarding actual
increase in length or thickness of the dental root due to
different angulations and image resolution. That was not
the case in our study due to radiographic standardization
using Image-J with Turbo Reg plug in.
There was no significant difference between propolis
and MTA subgroups regarding the change in root length
and thickness due to the control of infection that was
confirmed by the bacteriologic examination and the in-
duction of blood clot in all subgroups [9].
Regarding new hard tissue formation, there was no
significant difference between propolis and MTA sub-
groups along the three evaluation periods. The newly de-
posited hard tissue resembled cementum and had
cementocyte-like cells. These results are in accordance
with previous studies [18,30]. Regarding the tissue in-
growth, the nature of the regenerated tissue was pulp
like fibrous connective tissue with calcified bony islands
as well as cementum and without odontoblastic layer.
These findings are in agreement with the findings of pre-
vious studies [17,30]. On contrary, Tawfik et al. [14]
found a newly formed tissue resembles periodontal
tissue.
An interesting finding of this study is that some speci-
mens from the propolis group showed pulp like tissue
with the presence of odontoblastic layer. These findings
could be attributed to the abundance amount of multi
potent dental pulp stem cells in immature teeth, stem
cells of the apical papilla, or remnants surviving pulp
cells at the apical end of the root canal. These cells may
proliferate in the blood clot and differentiate into odon-
toblasts under the influence of cells of Hertwig’s epithe-
lial root sheath, which are resistant to destruction [31].
The ability of propolis to regenerate pulp is in accord-
ance with findings of other researches which reported
tubular dentin formation after pulp capping with
propolis [3,32].
The increase in root thickness by cementum depos-
ition on the inner dentinal wall and the presence of ce-
mentum and bone inside the root canal could be due to
delivering of mesenchymal stem cells from the bone and
periodontal ligament into the root canal during instru-
mentation for induction of bleeding. Another theory is
the blood clot itself which is rich in growth factors play-
ing a crucial role in regeneration [33].
Apical closure is the last stage of root maturation, no
significant difference was found between propolis and
MTA subgroups regarding apical closure. Similarly, ap-
ical closure was reported after revascularization of dogs
,
teeth with apical periodontitis [10].
General speaking, both radiographic and histologic
findings showed no significant difference between both
propolis and MTA subgroups at all evaluation periods,
therefore propolis can be considered a substitute of
MTA as a root canal orifice plug after revascularization.
Although toxicity data for propolis are scarce, few case
reports of allergic reactions have been recorded after
oral administration of propolis [34]. In our study, no al-
lergic reactions were recorded. This could be attributed
Fig. 5 (a) Photomicrograph for a sample of subgroup B (MTA) at 1
month showing dentin like tissue formation (H&E, X200). (b)
Photomicrograph for a sample of subgroup B showing pulp like
tissue with areas of osteoid like tissue inside the root canal and
closure of the apex (H&E, X100)
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 10 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
to application of propolis as intra-canal medicament and
root canal orifice plug.
Long follow up period is recommended for monitoring
of the regeneration process of the necrotic permanent
immature teeth. Also, further studies are recommended
for investigation of efficacy of propolis as an intra-canal
medication in infected mature teeth.
Conclusions
In conclusion, propolis reduces the bacterial counts in-
side the root canal and can be comparable with TAP as
intra-canal medicament in regenerative endodontic.
Moreover, both propolis and MTA as root canal orifice
plugs enhance an effective induction of hard tissue de-
position and soft tissue ingrowth in root canal space
after revascularization of necrotic immature permanent
teeth.
Abbreviations
CEJ: Cementoenamel junction; CFU: Colony-forming units; MTA: Mineral
trioxide aggregates; NaOCl: Sodium hypochlorite; RCC: Reduction in colony
counts; SD: Standard deviation; TAP: Triple antibiotic paste
Acknowledgements
Not applicable.
Authors’contributions
Dr. EMM: Animal study, analysis of the data. Prof. AMA: Animal study, writing
of the manuscript and supervision of the research. Prof. SHE: Review of the
manuscripts and supervision of the research project. Prof. SE: Microbiological
study. All authors read and approved the final manuscript.
Funding
No funding was received from any agency. This article was funded by the
authors.
Availability of data and materials
All data used and/or analyzed during this research are available from the
corresponding author on reasonable request.
Ethics approval and consent to participate
The present study was approved by the Ethical Committee at Faculty of
Dentistry, Ain Shams University, Egypt.
Consent for publication
Not applicable.
Competing interests
The authors declare that there are no competing interests in connection
with this article.
Author details
1
Department of Endodontics, Faculty of Dentistry, Ain Shams University,
Cairo, Egypt.
2
Department of Surgery, Anesthesiology & Radiology, Faculty of
Veterinary Medicine, Cairo University, Giza Square, Giza PO: 12211, Egypt.
3
Department of Microbiology & Immunology, Faculty of Medicine, Ain Shams
University, Cairo, Egypt.
Received: 27 October 2018 Accepted: 27 June 2019
References
1. Grange JM, Davey RW. Antibacterial properties of propolis (bee glue). J R
Soc Med. 1990;83:159–69.
2. Abu-Seida AM. Effect of propolis on experimental cutaneous wound healing
in dogs. Vet Med Int 2015, Article ID 672643, 4 pages.
3. Saleh R, Nagi SM, Khallaf ME, Abd El-Alim SH, Zaazou MH, Abu-Seida AM, et
al. In-Vivo assessment of dentin bridge formation after using MTA and
experimental propolis paste as direct pulp capping material. Res J
Pharmaceu, Biol Chem Sci. 2016;7(4):1244–50.
4. Ikeno K, Ikeno T, Miyazawa C. Effects of propolis on dental caries in rats.
Caries Res. 1991;25(5):347–51.
5. Krol W, Scheller S, Shani J, Pietsz G, Czuba Z. Synergistic effect of ethanolic
extract of propolis and antibiotics on the growth of staphylococcus aureus.
Arzneimittelforschung. 1993;43(5):607–9.
6. Awawdeh L, Al-Beitawi M, Hammad M. Effectiveness of propolis and
calcium hydroxide as a short-term intracanal medicament against
enterococcus faecalis: a laboratory study. Aust Endod J. 2009;35:52–8.
7. Kayaoglu G, Ömürlü H, Akca G, Gürel M, Gençay Ö, Sorkun K, Salih B.
Antibacterial activity of Propolis versus conventional endodontic
disinfectants against enterococcus faecalis in infected dentinal tubules. J
Endod. 2011;37(3):376–81.
8. Sato I, Kurihara-Ando N, Kota K, Iwaku M, Hoshino E. Sterilization of infected
root canal dentine by topical application of a mixture ciprofloxacin,
metronidazole and minocycline in situ. Int Endod J. 1996;29:118–24.
9. Thibodeau B, Trope M. Pulp revascularization of a necrotic infected
immature permanent tooth: case report and review of literature. Pediatr
Dent. 2007;29:47–50.
10. Bezerra da Silva L, Nelson-Filho P, Bezerra da Silva R, Flores DSH, Heilborn C,
Johnson JD, Preto R. Revascularization and periapical repair after
endodontic treatment using apical negative pressure irrigation versus
conventional irrigation plus triantibiotic intracanal dressing in dogs, teeth
with apical periodontitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod.
2010;109:779–87.
11. Wang X, Thibodeau B, Trope M, Lin LM, Huang GT. Histologic
characterization of regenerated tissues in canal space after the
revitalization/ revascularization procedure of immature dog teeth with
apical periodontitis. J Endod. 2010;36:56–63.
12. Nagy MM, Tawfik HE, Hashem A, Abu-Seida AM. Regenerative potential of
immature permanent teeth with necrotic pulps after different regenerative
protocols. J Endod. 2014;40:192–8.
13. El Ashry SH, Abu-Seida AM, Bayoumi AA, Hashem AA. Regenerative
potential of immature permanent non-vital teeth following different dentin
surface treatments. Exp Toxicol Pathol. 2016;68:181–90.
14. Tawfik H, Abu-Seida AM, Hashem AA, Nagy MM. Regenerative potential
following revascularization of immature permanent teeth with necrotic
pulps. Int Endod J. 2013;46:910–22.
15. Peciuliene V, Balciuniene I, Eriksen HM, Haapasalo M. Isolation of
Enterococcus faecalis in previously root-filled canals in a Lithuanian
population. J Endod. 2000;26:593–5.
16. Camp J, Fuks A. Pediatric endodontics: endodontic treatment for the
primary and young permanent dentition. In Cohen S, /Hargreaves K. Keiser
K, eds. Pathways of the pulp. 9
th
ed. St.louis: Mosby Elsevier; 2006: 822–882.
17. Torabinejad M, Turman M. Revitalization of tooth with necrotic pulp and
open apex by using platelet-rich plasma: a case report. J Endod. 2011;37:
1236–9.
18. Beccerra P, Ricucci D, Loghin S, Gibbs JL, Lin LM. Histological study of
human immature permanent premolar with chronic apical abscess after
revascularization. J Endod. 2014;40:133–9.
19. Ozan F, Sümer Z, Polat ZA. Ozan U and Deger O effect of mouth rinse
containing propolis on oral microorganisms and humsn gingival fibroblasts.
Eur J Dent. 2007;1:195–201.
20. Kouidhi B, Zmantar T, Bakhrouf A. Anti-cariogenic and anti-biofilms activity
of Tunisian propolis extract and its potential protective effect against cancer
cells proliferation. Anaerobe. 2010;16:566–71.
21. Arslan S, Ozbilge H, Kaya EG, Er O. In vitro antimicrobial activity of propolis,
BioPure MTAD, sodium hypochlorite, and chlorhexidine on enterococcus
faecalis and Candida albicans. Saudi Med J. 2011;32:479–83.
22. Calvalcante DR, Oliverira PS, Góis SM, Soares AF, Cadoso JC, Padilha FF, et al.
Effect of green propolis on oral epithelial dysplasia in rats. Braz J
Otorthinolaryngol. 2011;77:267–84.
23. El Ashry S, Abu-Seida AM, Al-Boghdady H, Abdel-Fattah M. The effect of
different formulations of calcium hydroxide on healing of intentionally
induced periapical lesions in dogs. Pak Vet J. 2013;3:48–52.
24. Hargreaves K, Law A. Regenerative endodontics. In: Hargreaves K, Cohen S,
editors. Pathways of the pulp. 10
th
ed. St.louis: Mosby Elsevier; 2011.
p. 602–19.
El-Tayeb et al. BMC Oral Health (2019) 19:174 Page 11 of 12
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
25. Kakoli P, Nandakumar R, Romberg E, Arola D, Fouad AF. The effect of age
on bacterial penetration of radicular dentin. J Endod. 2009;35(1):78–81.
26. Fabricius L, Dahlen G, Ohman AE, Moller AJ. Predominant indigenous oral
bacteria isolated from infected root canal after varied time of closure. Scand
J Dent Res. 1982;90:134–44.
27. Martin MP, Pileggi R. A quantitative analysis of Propolis: a promising new
storage media following avlusion. Dent Traumatol. 2004;20:85–9.
28. Keswani D, Pandey RK. Revascularization of an immature tooth with a
necrotic pulp using platelet-rich fibrin: a case report. Int Endod J. 2013;46:
1096–104.
29. Zhu W, Zhu X, Huang GT-J, Cheung GSP, Dissanayaka WL, Zhang C.
Regeneration of dental pulp tissue in immature teeth with apical
periodontitis using platelet rich plasma and dental pulp cells. Int Endod J.
2013;46:962–70.
30. Martin G, Ricucci D, Gibbs J, Lin L. Histological findings of revascularization/
revitalized immature permanent molar with apical periodontitis using
platelet rich plasma. J Endod. 2013;39:138–44.
31. Gronthos S, Brahim J, Li W, Fisher LW, Cherman N, Boyde A, et al. Stem cell
properties of human dental pulp stem cells. J Dent Res. 2002;81:531–5.
32. Ahangari Z, Naseri M, Abas F, Jalili M, Mansouri Y. Effect of propolis on
dentin regeneration in Guinea pig. Cell J. 2102(13):223–8.
33. Shah N, Logani A, Bhaskar U, Aggarawal V. Efficacy of revascularization to
induce apexification / apexogenesis in infected nonvital immature teeth: a
pilot clinical study. J Endod. 2008;34:919–25.
34. Basavaiah ND, Suryakanth DB. Propolis and allergic reactions. J Pharm
Bioallied Sci. 2012;4:345.
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