|Year : 2019 | Volume
| Issue : 1 | Page : 29-33
Comparative pH and calcium ion release in newer calcium silicate-based root canal sealers
Shekhar Shashank, Shikha Jaiswal, Vineeta Nikhil, Sachin Gupta, Preeti Mishra, Shalya Raj
Department of Conservative Dentistry, Subharti Dental College, Meerut, Uttar Pradesh, India
|Date of Web Publication||19-Jun-2019|
Dr. Shikha Jaiswal
Department of Conservative Dentistry, Subharti Dental College, Swami Vivekananda Subharti University, Meerut, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Aims: The aim of this study is to compare and evaluate pH and calcium ion release in newer calcium silicate-based root canal sealers.
Methodology: Polyethylene tubes were cut into 35 tubes of equal sizes; with each tube measuring 10 mm length × 1 mm diameter. The tubes were pre-weighted using digital weighing balance machine to allow a similar weight of each tube. The polyethylene tubes were divided into four groups according to the materials with which they were filled. Group 1 (n = 5) control group, Group 2 (n = 10) sealapex, Group 3 (n = 10) mineral trioxide aggregate (MTA) fillapex, and Group 4 (n = 10) White MTA. The tubes after being packed with the respective sealers were placed inside polypropylene flasks containing 10 ml of deionized water. The flask was closed and stored at a constant temperature of 37°C during all the evaluation period. At 24 h, 7 days and 1 month, pH and calcium ion released was measured using pH meter and atomic absorption spectrophotometer, respectively.
Results: At 24 h, White MTA showed the highest pH (8.52) and highest calcium (Ca++) release (14.7). At 7 days and 28 days, MTA fillapex showed significantly higher pH (8.64; 8.7) and Ca++ release (10.30; 18.60) than the other two groups.
Conclusion: Although at 24 h, the new calcium silicate-based root canal sealer, MTA fillapex showed the least Ca++ release but over longer time intervals, i.e., at 7 days and 28 days, MTA fillapex showed significantly higher pH and Ca++ release than both White MTA and sealapex.
Keywords: Calcium ion release, mineral trioxide aggregate fillapex, pH, sealapex, white mineral trioxide aggregate
|How to cite this article:|
Shashank S, Jaiswal S, Nikhil V, Gupta S, Mishra P, Raj S. Comparative pH and calcium ion release in newer calcium silicate-based root canal sealers. Endodontology 2019;31:29-33
|How to cite this URL:|
Shashank S, Jaiswal S, Nikhil V, Gupta S, Mishra P, Raj S. Comparative pH and calcium ion release in newer calcium silicate-based root canal sealers. Endodontology [serial online] 2019 [cited 2020 Jan 29];31:29-33. Available from: http://www.endodontologyonweb.org/text.asp?2019/31/1/29/260529
| Introduction|| |
The success of root canal therapy in endodontic practice mainly depends on obtaining a hermetic fluid tight seal at the apical end. According to Ostavik, sealer has an important role to play in sealing the root canal system with entombment of remaining microorganisms and filling of inaccessible areas of prepared canals. The introduction of sealers with therapeutic properties applied in endodontics conceivably created prospective of a higher success rate of root canal treatment.
Hence, the focus of research in sealers shifted toward calcium (Ca++) based sealers due to their antimicrobial activity owing to their Ca++ releasing potential. These sealers have been popularly used because of their potential for providing a high alkaline environment. The use of these materials create high alkalinity which aids in mineralization of hard tissue and provides good antimicrobial activity. The use of calcium hydroxide clinically in the root canal was first reported by Rohner in 1940. Calcium hydroxide-based sealers have since been in use and have remained popular. Among the variety of calcium hydroxide-based sealers available, sealapex is the most popularly used.
As a further improvement, calcium silicate-based materials were introduced of which MTA is the prototype. Mineral trioxide aggregate (MTA) was developed in 1990 at Loma Linda University and was idealized to be employed in numerous endodontic applications. Various studies have shown MTA to be biocompatible with the ability to stimulate mineralization and have the property of deposition of apatite-like crystals in dentin due to which its use was encouraged as a sealer.
In spite of the various favorable clinical properties, there are certain technical problems, for example, its handling is difficult due to its granular consistency, it has a prolonged setting time, and there remains the possibility of its displacement out of the cavity in which it is inserted., These drawbacks pose limitations in its use as s sealer.
To overcome these drawbacks, sealers-containing MTA were introduced, the latest among which is MTA Fillapex. According to the manufactures, the composition of this sealer is basically MTA incorporated with salicylate resin, natural resin, bismuth, and silica. Their good handling property makes them easier to be used in the canal as a sealer. However, there is limited research regarding the physiochemical and biological properties of MTA Fillapex.
Although several Ca++ based sealers are available in the market, the presence of diffuse Ca++ compounds in the composition of an endodontic sealer does not ensure the release of Ca++ and hydroxyl (OH−) ions after setting. During setting, the ions may not be released, or other components in the sealer may inactivate calcium hydroxide. Hence, it is necessary to evaluate pH and Ca++ release of these materials to analyze their alkalinization ability and induction of mineralization.
Hence, this study was designed to evaluate pH and calcium ion release of a new calcium silicate-based sealer-MTA Fillapex and compare it with White MTA and the conventional calcium hydroxide-based sealer-sealapex.
| Methodology|| |
“N” polyethylene tubes were cut into 35 tubes of equal sizes; with each tube measuring 10 mm length × 1.0 mm diameter using bard parker blade and digital Vernier caliper. The tubes were pre-weighed by a digital weighing balance machine to select similar weight tubes. The tubes were than prewashed with 5% nitric acid to prevent interference with phosphate ions and alkaline metals. The polyethylene mounted tubes were divided into three experimental and one control group according to the materials with which they were filled.
Distribution of the groups
- Group 1 (n = 5)-control group-empty tubes
- Group 2 (n = 10)-tubes filled with Sealapex
- Group 3 (n = 10)-tubes filled with MTA Fillapex
- Group 4 (n = 10)-tubes filled with White MTA.
Control group-Empty tubes-No sealer was used to fill the tubes in the control group.
Sealapex (Base and catalyst paste; ST-45 min).
Base and catalyst paste was taken on a mixing paper pad in a ratio of 1:1 and mixed according to the manufacturer's instructions till a uniform consistency was obtained. Sealer was filled into the polyethylene tubes using lentulo spiral.
MTA Fillapex (paste/paste system; ST-130 min).
The sealer was automixed with automixing tips to a uniform consistency and the mixed sealer was extruded on a mixing pad and lentulospiral was used to fill the sealer in the polyethylene tubes.
White MTA (powder and liquid system; ST-15 min).
The powder and liquid were taken in the ratio of 1:1 on a glass slab and spatulated with stainless steel spatula according to the manufacturer's instructions to a uniform consistency. The mixed MTA was carried into the polyethylene tube with the help of lentulo spiral. After complete filling of the tubes, the materials were condensed with the hand pluggers to avoid any voids in the inserted sealer. Subsequently, the samples were radiographed and those containing voids were discarded.
The filled polyethylene tubes were weighed to ensure a similar amount of material (±0.002 g) in each sample. Subsequently, the samples were placed in polypropylene flasks, containing 10 ml of deionized water. The deionized water was verified for the total absence of calcium ions and the presence of neutral pH (6.8). The flask was closed with the lid, and the samples were stored in an incubator at a constant temperature of 37°C during all the evaluation period. At 24 h, 7 days and 1 month, the deionized water was measured for pH by a pH meter and released calcium ions were measured by atomic absorption spectrophotometer. Following each evaluation, the water was discarded, and the samples were immersed in fresh deionized water of similar amounts (10 ml). All the data were subjected to statistical analysis by one-way ANOVA test and post hoc Tukey honestly significant difference test.
| Results|| |
At all-time intervals, all materials evaluated in the study exhibited an alkaline pH. The highest mean pH values observed at 24 h was shown by White MTA (8.52), whereas sealapex and MTA fillapex showed comparable pH (8.27). The highest mean pH values observed at 7 days was of MTA fillapex (8.64). There was no statistically significant difference between pH of White MTA and sealapex. At 28 days, MTA Fillapex showed significantly higher pH value (8.70) than other two groups (P < 000) [Table 1] and [Table 2].
|Table 1: Comparative mean pH values of the experimental groups at 24 h, 7 days and 28 days|
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|Table 2: Pair-wise comparison of pH between different groups at 24 h, 7 days, and 28 days with post hoc Tukey honestly significant difference test|
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Control group showed negligible Ca++ release at all time periods (0.03). All the experimental materials showed Ca++ release at all time periods.
The highest calcium ion release at 24 h was shown by White MTA (14.75) whereas MTA Fillapex showed significantly the lowest calcium ion release (5.77). At 7 days, MTA Fillapex showed the highest Ca++ release (10.30), whereas, Sealapex showed significantly lowest calcium ion release (8.24). At 28 days, the calcium ion release by MTA Fillapex was the highest (18.60), and the difference with other groups was statistically significant (P < 000) [Table 3] and [Table 4].
|Table 3: Comparative mean calcium ion release values (ppm) of the experimental groups at 24 h, 7 days, and 28 days|
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|Table 4: Pairwise comparison of calcium ion release between different groups at 24 h, 7 days and 28 days with post hoc Tukey honestly significant difference test|
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When pH and calcium ion release at different time intervals was compared, it was found that Sealapex showed a continuous decrease in pH and calcium ion release with increasing time intervals. The pH of White MTA showed an initial drop in pH and Ca++ at 7 days whereas, both the pH and calcium ion release increased at 28 days. MTA Fillapex showed a significant increase in the pH and calcium ion release with an increase in the period.
| Discussion|| |
The methodology used in the present study was similar to that used by Duarte et al.,, Polyethylene tubes were used rather than extracted teeth because the placement of the materials inside root canals may result in inaccurate results. It is difficult to standardize the size of the apical foramen in extracted teeth, and root dentin may also cause interference in the results. The close proximity of media to the oral tissue fluid-containing Ca++ and/or phosphate may be a source of calcium phosphate nucleation; hence deionized water was chosen as the storage media since use of saliva or oral tissue fluid may mask the release of calcium ions as saliva itself is a source of Ca++/phosphate and may lead to calcium phosphate nucleation.
Evaluations of pH and Ca++ release were performed at a period of 24 h, 7 days and 28 days. After each measurement, the specimens were carefully moved to new tubes with fresh deionized water to avoid the ionic saturation that would interfere in the outcomes.
Different pH values are observed with different formulations of MTA. The calcium hydroxide present in MTA and MTA based sealers dissociates into Ca++ and OH− ions on coming in contact with water thus increasing the pH of the solution. However, different pH values may be obtained with different materials due to the variation in the concentration of calcium hydroxide., Furthermore, although both White MTA and MTA Fillapex are MTA based sealers, but the size of the polymer chain formed after setting may vary which may explain the difference in the result.
The pH of White MTA angelus was in the range of 8.52 which is in accordance with the study done by Tanomaru-Filho et al. where White MTA exhibited a pH of 8.28. The pH value in the current study was found to be less than reported by Torabinejad et al. and Cutajar et al. (1995). The difference may be due to the difference in methodology. These authors used microelectrode to measure pH directly from the material mass instead of immersing tubes in water. The method described in our study has the advantage of not only allowing pH measurement at periods longer than the setting time but also actually measuring the materials' ability of alkalization.
The initial calcium ion release of White MTA was 14.8 ppm which was almost similar to the initial release evaluated by Tanomaru-Filho et al. MTA consists of 50%–75% of calcium oxide as compared to Sealapex which consists of 24 wt% of Ca++. This high percentage of calcium oxide in the composition may explain the high initial pH and high initial release of calcium ions shown by White MTA as compared to other experimental materials. The high initial pH and Ca++ may also be explained by the high initial solubility of MTA as assessed by Bodanezi et al., where MTA exhibited high initial solubility followed by a continuous decrease over 672 h. Similar results were also observed by Kuga et al. where White MTA showed a drop in pH and calcium ion release with an increase in time.
In this study, MTA Fillapex released calcium ions with an improving trend over time until a period of 28 days. This result is in accordance with the study done by Vitti et al., where MTA Fillapex showed a significantly continuous increase in Ca++ release which was 8.8 ppm in 24 h and 10.08 ppm in 28 days.
The phenomenon of increasing pH and Ca++ release over time can also be explained by the increased solubility of MTA Fillapex with time. When coming in contact with moisture initially, calcium silicates initiate a hydration reaction forming calcium silicate hydrogel and calcium hydroxide which may explain higher solubility results and calcium release.
In this study, Group 2 (Sealapex) showed an initial increase in pH at 7 days, but a decrease at 28 days and calcium ion release in Sealapex continuously decreases with time. The results of solubility studies also show a trend of decreased solubility of Sealapex with time. However, study done by Kuga et al. demonstrated a decrease in Ca++ release of Sealapex in 14 days followed by an increase in Ca++ release in 28 days.
MTA Fillapex showed higher Ca++ release than Sealapex which can be explained by the higher solubility of MTA Fillapex as was seen in the study by Borges et al. where the solubility of MTA Fillapex (14.85%) was more than Sealapex (5.65%). In a study by Nassari MRG et al., Fillapex presented a solubility of 16.6% at 2 days and 15.03% at 7 days, whereas Sealapex exhibited solubility of 13.42% at 2 days and 9.97% at 7 days. A decrease in solubility should manifest as a decrease in Ca++ release and a decrease in pH.
The increased solubility of MTA Fillapex is probably related to polymer degradation and cracks in the resin matrix which may facilitate water sorption leading to increasing calcium ion release. MTA Sealapex shows decrease solubility because of the highly hydrophobic component zinc stearate present in Sealapex, which prevents the ingress of water reducing the solubility in comparison to MTA Fillapex.
The better alkalinizing ability and Ca++ release of MTA Fillapex as compared to White MTA and (Sealapex) with increase in time intervals can be explained by greater solubility of MTA Fillapex with time as compared to the other two materials. However, further studies are needed to confirm the findings with a methodology which would probably better simulate the clinical situations.
| Conclusion|| |
At all-time intervals, all experimental materials exhibited an alkaline pH when immersed in deionized water. There was a statistically significant difference in pH and Ca++ release among the different sealers. Calcium silicate based sealers exhibited a higher pH and calcium ion release than calcium hydroxide-based sealer. Although at 24 h, MTA Fillapex showed the least Ca++ release but over longer time intervals, i.e., 7 days and 28 days, MTA Fillapex showed significantly higher pH and calcium ion release than White MTA and Sealapex.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]