Key words: Calcium hydroxide - Dentinal tubules - Metapex - Retreated root canals
INTRODUCTION
Root canal therapy eradicates bacteria from infected root canals and prevents reinfection.
Inappropriate mechanical debridement or persistence of bacteria in the root canal
structure due to poorly performed root canal therapy may lead to failure.[1 ] Failure of root canal treatment can be managed by nonsurgical retreatment. Calcium
hydroxide has been widely used in endodontics as an intracanal medicament because
of its bactericidal activities, especially in retreatment cases. This has also been
suggested for use as intracanal medicament because of its antiresorptive and tissue
dissolving properties.[2 ]
It was in 1920 that Herman introduced calcium hydroxide (Ca(OH)2 ) as a pulp capping agent, to the field of endodontics.[3 ] Ca(OH)2 is a white odorless powder having a molecular weight of 74.08. It has less solubility
in water (about 1.2 g/L at 25°C). Although it does not have property of bonding to
dentin, it has antibacterial property.[4 ] Ca(OH)2 exhibits lethal effects on bacteria as a result of damage to DNA, protein denaturation,
and the damage caused to cytoplasmic membranes. On common endodontic pathogens, it
is found to exhibit an extensive range of antimicrobial activities. Further, it maintains
high pH after setting, as the material dissolves readily in aqueous solution and liberating
hydroxyl ions. This high pH delivers an incentive for tooth to repair himself in nonexistence
of bacterial infection.[5 ]
Ca(OH)2 has low solubility in tissue fluids, even when there is direct contact with vital
tissues. It has an alkaline pH (about 12.5–12.8), which is chemically categorized
as a strong base. The material has the ability to quickly separate into hydroxyl ions
and calcium ions and maintain a high pH, and lead to bactericidal effects in the root
canal system.[6 ]
[7 ]
For Ca(OH)2 to perform efficiently as an intracanal medicament, hydroxyl ions must diffuse through
dentine. It is expected that this would occur in a similar manner with water because
dispersion through dentine is principally determined by molecular weight. Various
studies have attempted to identify the quantity of diffusion of hydroxyl ions into
the dentin using a diversity of experimental methods, comprising pH indicating solutions
or papers, pH values of the surrounding medium, and pH measurement of ground dentin.[5 ]
[6 ]
[7 ]
Ca(OH)2 controls infection and decrease the incidence of unfavorable symptoms. It is also
used in various clinical situations as an intracanal medicament, been shown to decrease
the pathogens associated with pulp necrosis, and limit root resorption and promote
the repair of periapical tissues.[8 ]
[9 ]
[10 ]
Kazemipoor et al ,[11 ] have stated that the difficulties which are more challenging in the retreated canals
are the openings of dentinal tubules which may be blocked with residual sealer and
gutta percha. This phenomenon can have an influence on the diffusion and penetration
of hydroxyl ions into the dentinal tubules.
Pashley and Livingston had suggested that hydrogen and hydroxyl ions like water should
diffuse readily through dentine since permeability was in general inversely related
to molecular size, and in this study where molecular charge was examined as a variable
it did not appear to influence the rate of diffusion.[12 ]
There are only limited studies that have examined the diffusion dynamic of hydroxyl
ions through dentinal tubules of retreated teeth. The present study was done to examine
the diffusion of Ca(OH)2 through dentinal tubules of retreated root canals using two different types of Ca(OH)2 preparations.
MATERIALS AND METHODS
A total of 45 extracted single rooted mandibular first premolars were taken for the
study. The teeth were cleaned from calculus and any remains of periodontal tissue
and kept in a thymol 10% solution till use.
Inclusion criteria
The inclusion criteria were as follows:
The premolars of patients aged between 16 and 20 years old, with single canal extracted
for orthodontic purpose were collected for this study
In the selected tooth, the presence of single root canal was verified using two digital
radiographs in both buccolingual and mesiodistal directions.
Exclusion criteria
Teeth with restorations, cracks, and open apices were excluded from the study.
Ethical approval was obtained from the Department of Conservative Dental Sciences,
College of Dentistry, Prince Sattam bin Abdulaziz University, before the study. All
the teeth used in this study were cleaned using running tap water and then stored
in normal saline. The crowns were transversally sectioned with a diamond cutting disc
at the cementoenamel junction level.
The length of the root canals was recorded at 1 mm short of the main apical foramen
and was standardized to nearly the same lengths (13 ± 1 mm) for all the sample teeth
as shown in [Figure 1 ]. Glyde (DENTSPLY, Maillefer) has been used as a lubricant. Root canals were prepared
using Protaper (DENTSPLY, Tulsa) rotary system files using an electric motor (X Smart;
DENTSPLY, Maillefer), till #F3 file. Irrigation during cleansing and shaping was accomplished
using distilled water. After instrumentation, a #30 file was introduced up to the
total length of the root canal for apical cleaning, and the root canal was then filled
with a solution of ethylenediaminetetraacetic (EDTA) (ULTRADENT, IndiSpense) for 3
min. The root canals were then cleansed with normal saline solution and then absorbent
paper points were used for drying. Then, all canals were obturated using cold lateral
condensation technique. Each tooth was placed in a container with unbuffered isotonic
saline soaked in cotton wool, which allows the sealer to set, kept in an oven at 37°C,
with 100% humidity for 7 days. After that, the gutta percha was removed from the canals
using chloroform and Protaper Universal Retreatment file # D3 (Protaper® Universal
Retreatment, DENTSPLY), along with the removal of certain amount of sound dentin.
The dentinal thickness in apical, middle, and coronal third was measured using digital
radiograph in mesiodistal and buccolingual direction as shown in [Figure 1 ]. Then, the selected teeth were randomly distributed into three groups, each group
comprising 15 teeth:
Figure 1: Peri–radicular radiograph showing the dentinal wall width of a sample
Group I: 15 root canals will not be filled with anything to be used as control group,
as shown in [Figure 2 ]
Group II: 15 root canals will be filled with a fresh mixture of calcium hydroxide
powder (Pulpdent Corporation, USA) and distilled water solution, as shown in [Figure 3 ]
Group III: 15 root canals will be filled with oily readymade calcium hydroxide Metapex
(Meta Biomed, Korea), as shown in [Figure 4 ].
Figure 2: Peri–radicular radiograph showing a sample from control group
Figure 3: Peri–radicular radiograph showing freshly mixed Ca(OH)2 inside the canal with the coronal and apical amalgam seals of a sample from Group
II
Figure 4: Peri–radicular radiograph showing Metapex inside the canal group, Group II = calcium
hydroxide, and Group III = Metapex) in the with the coronal and apical amalgam seals
of a sample from Group III four tested periods (7 days, 10 days, 14 days, and 30 days)
The coronal access cavities and the apical openings were sealed with amalgam restoration.
Each specimen was kept in small vial with 30 ml of deionized water kept in an oven
at 37°C, with 100% humidity; to be used for pH measurements after 7, 10, 14, and 30
days using pH meter.
When measuring the pH, the tooth was removed from the vial and rinsed with saline.
At the end of each stage, the teeth were placed back in the same vial with freshly
placed cotton saturated with saline.
RESULTS
The average baseline pH in control group was similar (pH 6.9–7.4). The pH values of
both Ca(OH)2 was between 9.2 and 11.2 when measured in all the four periods which were highly
significant than the negative control group.
[Table 1 ] shows the mean of pH readings of the control group after 7, 10, 14, and 30 days.
The pH value dropped after 14 and 30 days, while no significant change in the pH after
7 and 10 days.
Table 1:
Mean of pH readings of Group I (Control Group)
pH readings of group I
Sample no.
Mean
After 7 days
After 10 days
After 14 days
After 30 days
1
7.336
8.236
6.808
6.928
2
7.420
8.034
6.484
6.798
3
7.296
7.986
7.004
6.726
4
7.420
8.236
6.388
6.720
5
7.570
8.002
6.688
7.770
6
7.276
7.950
6.528
6.608
7
7.362
7.762
6.802
6.716
8
7.360
8.034
6.484
6.798
9
7.296
7.986
7.004
6.726
10
7.420
8.236
6.388
6.720
11
7.570
8.002
6.688
7.770
12
7.276
7.950
6.528
6.608
13
7.362
7.762
6.802
6.716
14
7.296
8.236
6.808
6.798
15
7.420
8.034
6.484
6.726
[Table 2 ] shows mean of pH readings of freshly mixed calcium hydroxide group after 7, 10,
14, and 30 days. The pH reading was shown an increase after 10 and 14 days, while
no significant increase in pH after 30 days.
Table 2:
Mean of pH readings of Group II (Calcium Hydroxide Group)
pH readings of group II
Sample no.
Mean
After 7 days
After 10 days
After 14 days
After 30 days
16
10.555
11.764
9.866
8.250
17
10.320
11.250
10.932
9.678
18
11.086
11.778
10.956
8.452
19
10.450
11.778
10.000
8.786
20
10.088
11.778
11.072
10.550
21
10.498
11.246
10.702
9.170
22
10.650
11.720
10.028
10.204
23
9.854
10.822
10.402
9.558
24
9.532
10.548
9.724
8.994
25
10.436
11.550
10.802
8.878
26
9.458
9.844
7.826
7.646
27
10.766
11.674
10.178
8.862
28
8.356
9.200
7.994
9.156
29
11.280
11.222
10.822
10.896
30
11.594
11.918
9.536
8.124
[Table 3 ] shows the mean of pH readings of Metapex group after 7, 10, 14, and 30 days and
no significant change in the reading in the pH was noticed.
Table 3:
Mean of pH readings of Group III (Metapex Group)
pH readings of group III
Sample no.
Mean
After 7 days
After 10 days
After 14 days
After 30 days
31
8.902
7.166
9.144
8.192
32
8.180
8.594
8.194
10.160
33
11.098
10.484
10.346
9.308
34
10.184
10.270
10.832
9.258
35
10.260
8.882
10.772
9.374
36
10.130
10.648
11.356
9.722
37
9.890
10.154
11.124
9.310
38
11.008
10.444
11.218
9.380
39
10.962
10.062
10.772
9.186
40
10.126
10.256
10.440
9.560
41
9.198
8.202
10.356
8.038
42
8.958
7.212
9.458
9.984
43
10.290
10.192
10.268
8.548
44
9.862
9.722
11.156
8.922
45
10.446
9.686
11.308
9.186
After 7 and 10 days, freshly mixed Ca(OH)2 showed the higher pH than the creamy Metapex, and statistically, the difference was
highly significant after 10 days (P <0.001).
After 14 days, Metapex group pH was higher than freshly mixed Ca(OH)2 , but it was not statistically significant, they reached the same pH after 30 days
(P >0.05). Descriptive statistics using one way ANOVA test was used to compare the pH
values for different types of Ca(OH)2 at different time periods and multiple comparisons post hoc test was used in this study to get the results [Table 4 ].
Table 4:
Descriptive Statistic one way ANOVA test and multiple comparisons post hoc test
n
Descriptive (one way)
Multiple comparisons (post hoc test)
Group I (Control) Mean±SD
Group II Ca (OH)2 Mean±SD
Group III (Metapex) Mean±SD
P
PI and II
PI and III
PII and III
Ca(OH)2 : Calcium hydroxide, SD: Standard deviation
Day 7
7.398±0.108
10.328±0.804
9.966±0.838
0.000
0.000
0.000
0.193
Day 10
7.029±0.166
11.206±0.796
10.00±1.171
0.000
0.000
0.000
0.000
Day 14
6.672±0.217
10.056±0.998
10.450±0.898
0.000
0.000
0.000
0.222
Day 30
6.895±0.398
9.295±0.906
9.209±0.591
0.000
0.000
0.000
0.815
[Graph 1 ] presents the comparison of the changes in the pH reading of all the three groups
after 7, 10, 14, and 30 days. The control group does not show any significant change
in the pH reading, while the Group III has shown changes in the pH reading, but it
was less as compared to the Group II [Graph 1 ].
Graph 1: The mean of pH values of the three test groups (Group I = control group, Group II
= calcium hydroxide, and Group III = Metapex) in the four tested periods (7 days,
10 days, 14 days, and 30 days)
DISCUSSION
The desired beneficial effect of Ca(OH)2 is dependent on its separation into hydroxyl ion and calcium ion, and their diffusion
through the dentinal tubules and the apical foramen. When the hydroxyl ions diffused,
the pH will be raised causing destruction of bacteria, reduction of osteoclastic activity,
inactivation of bacterial enzymes, and activation of alkaline phosphatase which is
involved in mineralization.[10 ] Diffusion of Ca(OH)2 through dentinal tubules has been studied in the recent years.[13 ]
[14 ]
According to Ba Hattab et al ,[15 ] The hydroxyl ions release in an aqueous environment is necessary for antimicrobial
activity of calcium hydroxide. Hydroxyl ions react intensively with biomolecules because
of their free radicals. As this reactivity is unspecified, the free radicals most
likely gathered at the sites of generation.
For the medications to show complete efficacy, they have to be in contact with the
dentin for certain period and also be able to enter the dentinal tubules. Therefore,
the intracanal medicaments’ proper wetting with the radicular dentine and contact
angle between the hard tissue and the paste should be considered.[16 ] According to Kontakiotis et al ,[17 ] wetting of aqueous liquid means that, an edge contact is being molded between a
liquid and a solid with a concurrent exclusion of air. The propensity of a liquid
to wet a solid surface is conveyed with the development of a contact angle. Principally,
the lower the angle, the faster the liquid medium will wet on the tooth surface, and
a contact angle of <90° designates good wetting properties.
Madarati et al,[18 ] conducted a study, in which participants were aware that the main function of intracanal
medicaments is disinfection of the root canal system, where Ca(OH)2 was used as an intracanal medicament in necrotic pulp cases.
The study conducted by Rizvi et al ,[19 ] states that MTAD is effective in the eradication of Enterococcus faecalis, around neutral pH, the effective inhibition of E. faecalis is better than the other root canal irrigants investigated in this study such as
sodium hypochlorite, EDTA, and chlorhexidine
Yücel et al ,[20 ] stated that for proper wetting of the canal wall, Ca(OH)2 powder has been used as a mixture for root canal dressing and can be mixed with vehicles
such as olive oil, glycerin, propylene glycol, iodoform plus saline solution, camphorated
parachlorophenol plus glycerin, camphorated parachlorophenol, methylcellulose, metacresylacetate,
saline, distilled water, anesthetic solutions, Ringer’s solution, and camphorated
monochlorophenol cresatin.
Besides permitting diffusion of the Ca(OH)2 , the vehicle can enhance the antimicrobial capacity of the paste. [21 ] According to Gomes et al ,[22 ] chlorhexidine can be used as a vehicle for attempting an increase in the antimicrobial
property to be effective against aerobic and facultative anaerobic microorganisms,
Gram.positive and Gram.negative microorganisms, yeasts, and viruses.
Only a few studies have evaluated the dissolution [18 ]capacity of Ca(OH)2 preparations in retreated cases. During the root canal retreatment procedure, the
dentinal tubules openings may be obstructed with gutta-percha and the remaining sealer.
This can impact on the penetration and diffusion of hydroxyl ions through dentinal
tubules. Hence, we intended to remove sound dentin during removal of the gutta-percha.
The permeability of dentin is directed mostly by dentin tubule anatomy, diameter,
density, and length as well as features of the solute such as charge and size. Dentin
is a substrate, whereas calcium hydroxide is a material. The size of the dentin tubules
correlates with the size of the Ca(OH)2 particles.[23 ]
[24 ]
In the present study, in one group, we used Ca(OH)2 powder mixed with distilled water; and in the other group, we used oily Metapex composed
of Ca(OH)2 , iodoform, and silicon oil to fill the canals of retreated roots. To simulate the
clinical condition, samples were kept in incubator at 37°C during the testing periods.
According to the condition of our study, the normal baseline pH in negative control
group was similar (pH 6.9-7.4). Both Ca(OH)2 types showed pH values between 9.2 and 11.2, when measured in all the four periods
which were highly significant than the negative control group and these are consistent
with most studies.[25 ]
[26 ]
[27 ]
After 7 and 10 days, freshly mixed Ca(OH)2 showed higher pH than the creamy Metapex. Statistically, the difference was found
to be highly significant after 10 days. This means that the diffusion of hydroxyl
ions of freshly mixed Ca(OH)2 is more than that of oily Metapex, and this result is consistent with Larsen and
Horsted-Bindslev.[28 ] It was also observed that oil paste containing Ca(OH)2 was having low solubility and were mainly deficient in both ion release and antimicrobial
properties. The aqueous suspension showed the highest pH and calcium ion liberation.
After 14 days, Metapex group pH was higher than freshly mixed Ca(OH)2 but was not statistically significant. This could be due to Metapex comprising of
Ca(OH)2 and iodoform mixture in silicon oil. The low solubility and diffusibility could preserve
the high pH till 14 days. The pH of both Ca(OH)2 preparations reached nearly the same after 30 days.
CONCLUSION
The freshly mixed Ca(OH)2 showed the higher pH after 7 and 10 days than that of the Metapex. Significant statistical
difference was observed after 10 days. For Metapex group, pH was higher than freshly
mixed Ca(OH)2 after 14 days. However, it was not statistically significant. After 30 days, Metapex
group attained the same pH as that of the Ca(OH)2 . Thus, Ca(OH)2 preparations showed higher pH after 7, 10, 14, and 30 days, while the Metapex in
our study continued to have higher pH after 14 days but achieved nearly the same pH
after 30 days as that of the Ca(OH)2 .
Financial support and sponsorship
Nil.
