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Table of Contents   
ORIGINAL ARTICLE  
Year : 2023  |  Volume : 26  |  Issue : 1  |  Page : 42-46
Evaluation of pH and calcium ions release of two tricalcium silicate-based sealers through roots of primary teeth


Department of Dentistry, Federal University of Santa Catarina, Florianopolis, Santa Catarina, Brazil

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Date of Submission06-Jul-2021
Date of Decision06-Sep-2021
Date of Acceptance11-Oct-2021
Date of Web Publication17-Aug-2022
 

   Abstract 

Background: This study aimed to evaluate the pH and calcium ions (Ca2+) release from two tricalcium silicate-based sealers (Sealer Plus BC and Bio-C Pulpecto) through roots of primary teeth.
Methods: Forty root canals of primary incisors were prepared and distributed into four groups according to the filling material: GPlusBC (Sealer Plus BC); GBioC (Bio-C Pulpecto); GUltra (Ultracal); and GC (no filled). pH measurement was performed with a digital pH meter, and the Ca2 + release was measured in an atomic absorption spectrophotometer at baseline, 24 h and 1, 2, 3, and 4 weeks later. The data were analyzed using two-way ANOVA and Tukey's post hoc tests.
Results: The results did not reveal significant differences between the groups in terms of pH in 24 h, 1-, and 2-weeks' periods. After 4 weeks, there was a significant difference, with the highest mean pH values in GUltra, followed, respectively, by GPlusBC and GBioC. Regarding the Ca2 + release, the GUltra showed greatest mean values at all evaluated times, and the other groups showed no difference between them.
Conclusion: Both sealers were able to promote the elevation of the pH and Ca2 + release through roots of primary teeth, which brings favorable properties for their use as a filling material.

Keywords: Calcium release; calcium silicate; pH; primary teeth; root canal sealer

How to cite this article:
da Silva AR, Bortoluzzi EA, Vitali FC, Bolan M, Cardoso M. Evaluation of pH and calcium ions release of two tricalcium silicate-based sealers through roots of primary teeth. J Conserv Dent 2023;26:42-6

How to cite this URL:
da Silva AR, Bortoluzzi EA, Vitali FC, Bolan M, Cardoso M. Evaluation of pH and calcium ions release of two tricalcium silicate-based sealers through roots of primary teeth. J Conserv Dent [serial online] 2023 [cited 2023 Feb 6];26:42-6. Available from: https://www.jcd.org.in/text.asp?2023/26/1/42/353904

   Introduction Top


Primary teeth pulpectomy must ensure that physiological exfoliation occurs normally.[1] Some particularities should be taken into account by the clinician during this procedure, such as the filling material, which ideally should have a degree of resorption similar that of the root.[1],[2] Zinc oxide eugenol (ZOE), traditionally used as a filling material, has a slower resorption rate than the physiological resorption process.[2] Calcium hydroxide (CH)-based pastes, mainly used for their biological and antibacterial properties, has a faster resorption speed than the root.[2]

CH has the ability to dissociate into hydroxyl and calcium ions when used inside the root canal.[3],[4] The hydroxyl has the ability to diffuse through exposed dentinal tubules, increasing the pH of the root surface.[3],[4] This increase has a beneficial effect in attenuating inflammation and creates a medium that favors repair.[3],[4]

The use of tricalcium silicate-based materials as root canal sealers is promising in primary teeth therapy for presenting favorable physicochemical and biological properties.[5] These materials have properties such as biocompatibility and nonshrinkable and were chemically stable, and the resorption may occur simultaneously with the rhizolysis.[6],[7] The good performance of these sealers is largely attributable to their ability to release hydroxyl and calcium after the setting reaction.[5],[8] Previous study evaluated the diffusion rate of hydroxyl and calcium through the root dentin of permanent teeth filled with calcium silicate-based materials,[9] however, this evaluation has not yet been performed on primary teeth.

Pulpectomy research on primary teeth is still looking for a better filling material. Among the steps that aim to identify the most suitable material, the verification of a material capable of diffusing the hydroxyl and calcium can be highlighted. Thus, the present study aimed to evaluate the pH and calcium ions release through roots of primary teeth filled with two tricalcium silicate-based sealers. The null hypothesis was that there is no difference between the sealers on hydroxyl and calcium ions diffusion through root dentin.


   Methods Top


Ethical approval

Ethical approval was obtained from the Local Ethics Committee on Human Research (n. 35533). The sample size was calculated with the Sealed Envelope software (https://sealedenvelope.com/), considering a reliability level of 90%, power of 80%, and a significance level of 5%. Accordingly, 40 primary teeth were selected.

Sample selection

Forty single-rooted extracted primary incisors were selected. The teeth were stored in 10% formaldehyde for 48 h, transferred to 0.9% saline solution and kept at 4°C. After cleaning the roots with periodontal curettes, the teeth were immersed in 5.25% sodium hypochlorite (NaOCl) (Asfer, São Paulo, Brazil) for 30 min, rinsed in distilled water, examined under an operative microscopy (DF Vasconcellos, Valença, Brazil), and submitted to periapical radiographs. Eligibility criteria were single straight canal, presence of 2/3 or more root length, absence of caries lesions and calcifications, no perforating resorption, and no previous endodontic treatment. Roots with <2/3 root length and cracks or fractures were excluded. All roots were transversely sectioned 8-mm apical and 2-mm coronal to the cementoenamel junction with a double-face diamond disk (KG Sorensen, São Paulo, Brazil), to obtain a standardized root length of 10 mm. All measurements were confirmed with a digital caliper (Digimess Precision, São Paulo, Brazil).

Endodontic procedures

After the root canal access, a size #15 K-file (Dentsply Maillefer, Baillagues, Switzerland) was introduced into the root canal until its tip was visible in the foraminal opening with a ×10 magnification. The working length (WL) was established 1 mm short of the end of the root canal. Root canal preparation was performed with manual files (Dentsply Maillefer, Baillagues, Switzerland) until a master apical file size #40/0.02. During preparation, the root canals were irrigated with 1% NaOCl at each file and finally irrigated with 3 mL of ethylenediaminetetraacetic acid (EDTA) 17% (Biodinamica, São Paulo, Brazil) and 3 mL of 1% NaOCl for smear layer removal. After preparation, the root canals were irrigated with 10 mL of distilled water and dried with absorbent paper points.

The external root surface was marked with a graphite pencil to guide the cementum removal, which was performed with diamond burs and periodontal curettes. Thereafter, the root apexes were coated with one layer of a fast-setting cyanoacrylate (SuperBonder, São Paulo, Brazil) and, after 24 h, two additional coats of nail varnish (L'Oréal, Rio de Janeiro, Brazil) to complement the waterproofing. Before and after filling the canals, each tooth was weighed on a precision scale (BioPrecisa, Rio de Janeiro, Brazil).

The specimens were randomly distributed into four groups (n = 10): GPlusBC: Sealer Plus BC (MK Life, Porto Alegre, Brazil); GBioC: Bio-C Pulpecto (Angelus, Parana, Brazil); GUltra: Ultracal/positive control (Ultradent, South Jordan, USA); and Gc: Negative control (unfilled canals). Each sealer was mixed according to the manufacturer's instructions. A single operator performed all the procedures.

The sealers were inserted into the canals to 1 mm short of the WL using a cannula recommended by the manufacturer following a #25 Lentulo drill (Dentsply Maillefer, Baillagues, Switzerland). Periapical radiographs were performed to confirm the complete filling of the root canals. A 2-mm-thick sealing was placed at the root canals entrance using a gutta-percha slice and composite resin (FGM, Santa Catarina, Brazil). Two coats of nail varnish were placed on the margins of the sealing and cement-enamel junction. The specimens were individually stored in deionized water under 100% relative humidity at 37°C.

pH and calcium ions release

The pH of the medium of each sample was assessed using a calibrated digital pH meter (Hanna, São Paulo, Brazil). Readings were performed after 2 min of immersion of the electrode in each flask. Measurements were taken at regular intervals (baseline, 24 h, and 1, 2, 3, and 4 weeks), with the temperature and pH of each sample recorded for each reading. Before each measurement, the basal pH (5.6) of the water used for submersion of the specimens was confirmed. After the pH reading, each specimen was transferred to a new medium containing 10 mL of deionized water, and the previously used solution was acidified with hydrochloric acid until it reached a pH close to 2.0 and stored at 4°C until submitted to analysis. A calibrated atomic absorption spectrometer (PerkinElmer, São Paulo, Brazil) was employed for the determination of calcium concentration. Before the analysis, a reading was performed of medium used in the study to determine whether it contained calcium, establishing the baseline for the equipment. The amount of calcium and pH were determined for subsequent analysis.

Statistical analysis

Statistical analysis was performed with the Statistical Package for the Social Sciences version 21.0 (IBM SPSS Statistics, Chicago, Illinois, USA). Data normality was confirmed by the Shapiro–Wilk test (P = 0.200). To analyze the changes in pH and calcium ions release in each group throughout the periods, the two-way analysis of variance and Tukey's HSD post hoc test were applied. The level of significance was 5%. Spearman's correlation was applied to determine associations between the weight of material used to teeth filling with the pH and calcium release.


   Results Top


[Table 1] shows the mean pH values in the groups over the periods. There was a significant difference in the pH variation between the groups and periods (P < 0.01). Significant difference was observed after 3 weeks (P < 0.01), with the highest mean pH values in GUltra. After 4 weeks, there were significant differences between all groups, with the highest mean pH values in GUltra, followed, respectively, by GPlusBC, GBioC, and GC (P < 0.05). No differences were found between the groups at 24 h, 1, and 2 weeks. The performance of the groups over the periods was different. GBioC shows an increase in the mean pH value after 24 h until 2 weeks, and GUltra after 24 h until 3 weeks (P < 0.01), remaining stable after those periods. GPlusBC and GC showed no difference in the mean pH value in the evaluated periods. [Figure 1] shows the distribution of the mean pH values of the groups over the periods.
Table 1: Mean (standard deviation) values of pH measurements and calcium ions release (mg/L) observed at the different periods

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Figure 1: Distribution of mean pH values of the groups over the studied periods

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[Table 2] shows the mean diffusion of calcium ions over the periods. There was a significant difference in the mean values of calcium release between groups and periods (P < 0.01). GUltra showed greatest calcium diffusion (P < 0.01), the other groups showed no difference between them. The performance of the groups over the periods was different, GUltra showed an increase in the mean of calcium diffusion at all times evaluated, and GBioC showed an increase between the 2nd and 4th weeks (P < 0.05), while the other groups did not show any difference between the evaluated times. [Figure 2] shows the mean diffusion of calcium over the periods.
Table 2: Mean (standard deviation) values of calcium ions release (mg/L) observed at the different periods

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Figure 2: Mean quantity of calcium ions released (mg/L) of the groups over the studied periods

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The amount of material used for teeth filling had no correlation to pH (r = 0.306; P = 0.106) and calcium release (r = 0.130; P = 0.404).


   Discussion Top


The increasing use of tricalcium silicate-based materials is mainly due to its high biocompatibility and antibacterial activity.[6] Its use is promising in pediatric dentistry because they are materials with favorable properties for filling primary teeth, such as the speed of root resorption, which may occur simultaneously with root rhizolysis.[6],[7] This fact does not occur with other root filling materials, such as ZOE.[2] This study evaluated the pH and calcium ions release through the root of primary teeth filled with Sealer Plus BC and Bio-C Pulpecto. The results demonstrated that Sealer Plus BC showed highest mean pH values after 4 weeks, however, there was no difference between the sealers regarding the calcium release. Thus, the hypothesis was partially rejected.

The results showed that after 24 h until 2 weeks, there was no difference between the groups in terms of pH of the medium in which the specimens were immersed. However, Ultracal showed the highest mean values after 4 weeks, followed by Sealer Plus BC and Bio-C Pulpecto. The therapeutic effects of CH depend on its dissociation into hydroxyl and calcium ions and on the availability of hydroxyl to increase the pH of the medium, therefore, the greater number of hydroxyl, the higher the pH.[10] The greater diffusion of hydroxyl in the Ultracal was expected once the material is a paste.[9],[11] Factors influencing the speed of ionic diffusion include the CH vehicle.[9],[10] Furthermore, previous studies have shown that the presence of smear layer and root cement can also affect the ions diffusion through the root dentin.[9],[10],[12] In the present study, the smear layer removal was performed using EDTA and NaOCl, to simulate a clinical situation and favor the sealers action.[13] The root surface had the cementum removed to allow a better analysis of the ions diffusion. Other authors have shown that the presence of cementum can hinder or prevent ion diffusion through the root dentin due to its impermeability.[12],[14]

In the first 2 weeks, the pH of the medium was similar between bioceramic sealers and Ultracal. This shows a good performance of the sealers since the increase in pH promoted by CH was effective in previous studies.[15],[16] However, the minimum amount of pH capable of rendering a nonviable medium for bacterial survival is not completely known.[11] What is expected is that the materials will be able to release as much hydroxyl as possible to promote alkalization.[15] Previous studies have shown that the presence of a more acidic environment favors the hydroxyl diffusion, as there is a tendency toward neutralization.[15] Thus, it can be suggested that the diffusion in vivo would be greater due to the presence of an acidic environment caused by inflammatory processes or by the presence of the apical foramen or resorption areas of the primary tooth.[11] High pH values are important for primary teeth filling because it is fundamental to achieve adequate disinfection and promote repair.[17],[18]

Sealer Plus BC is an aluminum and resin-free sealer, insoluble, and radiopaque.[5],[19] It has an additional amount of CH in its matrix composition, responsible for its alkalizing activity.[19],[20] Previous studies have indicated that the addition of CH to endodontic sealers improves their biological properties.[20] Mendes et al.[19] evaluated the hydroxyl and calcium diffusion from this sealer and observed higher mean values regarding pH and calcium release. However, the authors evaluated ionic diffusion in polyethylene tubes, and not in primary teeth roots. In addition, the medium in which the roots were immersed was not replaced daily to obtain the maximum ion diffusion without saturating. The ions diffusion through the root dentin showed better results than previous studies, however, the pH of the medium was similar.[19] Another study also found higher levels of calcium release for bioceramics.[19] The presence of high levels of calcium favors the formation of an alkaline pH, leading to a biochemical effect that accelerates the healing process, a desirable property of a filling sealer.[21],[22]

Bio-C Pulpecto is a ready-for-use material developed specifically for primary teeth filling.[6] A previous study demonstrated that this sealer presented biocompatibility and capacity for biomineralization similar to MTA.[6] The present study is the first to analyze the ions diffusion from this sealer. No significant differences were found in the alkalinization of the medium between this sealer and CH in 24 h until 2 weeks, indicating that these periods are equivalent in terms of pH. However, after the 4th week, its performance was below CH and Sealer Plus BC. Regarding the calcium release, there is no increase on ion levels over the evaluated times. Previous studies that evaluated the ionic release of a sealer with a similar composition (Endosequence BC; Brasseler, USA) demonstrated a higher calcium release in the period of 240 h, which is controversial with our results.[6] However, their evaluation was not made on roots of primary teeth, but on precast discs submerged in saline solution.

The control group showed an increase in the pH of the medium and the calcium release. The same was observed by Ximenes and Cardoso[11] in the evaluation of ions diffusion from CH-based medications. However, these results differ from those found by other authors, where there was no increase in pH or calcium release.[23],[24] The explanation of the different results may be due to the nature of the specimens. When the primary teeth roots were used,[11] an increase in the ions diffusion was observed. This increase may be attributed to the hydroxyl and calcium release from the root dentin due to its buffer effect.[24] The other studies used polyethylene tubes, which explain the lower ion diffusion rate.[23],[24]

The resorption rate of paste-based filling materials is faster than the primary teeth physiological resorption, whereas the sealers have slower speed than rhizolysis.[2] Based on this, the use of tricalcium silicate-based materials, which have a similar resorption speed, is promising in pediatric dentistry.[6],[7],[25] In addition, the present study showed that bioceramics can have a slow and constant diffusion of hydroxyl and calcium release during the time they remain in the tooth, which has a very interesting bacterial and repair inducing effect.

The present study has limitations for being in vitro. When assessing the ionic diffusion rate in vivo, other factors may influence the results, such as the presence of resorption, an open apex, inflammatory process, or the pH of the medium.[11] Therefore, more studies must be carried out to acquire greater knowledge of the performance of bioceramics as primary teeth filling materials.


   Conclusion Top


Bio-C Pulpecto and Sealer Plus BC were able to increase the pH and calcium release through the root dentine of primary teeth, which brings favorable properties for their use as a filling material for these teeth.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Barbosa VM, Pitondo-Silva A, Oliveira-Silva M, Martorano AS, Rizzi-Maia CC, Silva-Sousa YT, et al. Antibacterial activity of a new ready-to-use calcium silicate-based sealer. Braz Dent J 2020;31:611-6.  Back to cited text no. 18
    
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Benetti F, de Azevedo Queiroz ÍO, Oliveira PH, Conti LC, Azuma MM, Oliveira SH, et al. Cytotoxicity and biocompatibility of a new bioceramic endodontic sealer containing calcium hydroxide. Braz Oral Res 2019;33:e042.  Back to cited text no. 20
    
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22.
Candeiro GT, Correia FC, Duarte MA, Ribeiro-Siqueira DC, Gavini G. Evaluation of radiopacity, pH, release of calcium ions, and flow of a bioceramic root canal sealer. J Endod 2012;38:842-5.  Back to cited text no. 22
    
23.
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24.
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25.
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Correspondence Address:
Prof. Mariane Cardoso
Department of Dentistry, Health Sciences Center, Federal University of Santa Catarina, Florianopolis 88040-900, Santa Catarina
Brazil
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcd.jcd_355_21

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