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Year : 2016  |  Volume : 28  |  Issue : 2  |  Page : 114-118

Calcium ion release from four different light-cured calcium hydroxide cements

Department of Conservative Dentistry and Endodontics, M.A. Rangoonwala College of Dental Sciences and Research Centre, Pune, Maharashtra, India

Date of Web Publication9-Dec-2016

Correspondence Address:
Wasifoddin A Chaudhari
Department of Conservative Dentistry and Endodontics, M.A. Rangoonwala College of Dental Sciences and Research Centre, Azam Campus, Pune - 411 001, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0970-7212.195426

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Introduction: The aim of this study was to compare calcium (Ca) ion-releasing capacity of four different light-cured calcium hydroxide [Ca(OH)2] cements with self-cured Ca(OH)2cement.
Materials and Methods: Five different brands of Ca(OH)2cements were taken and they were grouped into five groups which are as follows: Group I - Dycal (control group), Group II - Septocal, Group III – TheraCal, Group IV - Cal LC, and Group V - Hydrocal. All specimens (n = 50) were prepared by mixing and curing the cements as per manufacturer's instructions. Each sample was placed on the bottom of a 4 cm high test tube in 10 ml deionized water at 37°C. This stored water was collected for Ca analysis and replaced after 7, 14, and 21 days. In this manner, ion release was measured after 7, 14, and 21 days by inductively coupled plasma-optical emission spectroscopy test.
Results: Ca ion release from all groups at various time durations was measured and mean was calculated along with the standard deviation. These values were compared using two-way ANOVA and Tukey's post hoc test which showed highly significant result with P< 0.001.
Conclusions: Within the limitations of this study, light-cured Ca(OH)2cements released high amount of Ca ions compared to self-cured Ca(OH)2cements. Group V (Hydrocal) and Group III (TheraCal) were found to be the highest light-cured Ca ion releasing materials.

Keywords: Bioactive; biocompatible; biointeractive; calcium hydroxide cement; direct pulp capping and indirect pulp capping; reparative dentin; secondary dentin.

How to cite this article:
Chaudhari WA, Jain RJ, Jadhav SK, Hegde VS, Dixit MV. Calcium ion release from four different light-cured calcium hydroxide cements. Endodontology 2016;28:114-8

How to cite this URL:
Chaudhari WA, Jain RJ, Jadhav SK, Hegde VS, Dixit MV. Calcium ion release from four different light-cured calcium hydroxide cements. Endodontology [serial online] 2016 [cited 2022 Nov 30];28:114-8. Available from: https://www.endodontologyonweb.org/text.asp?2016/28/2/114/195426

  Introduction Top

Pulp capping materials are placed or coated as a protective layer on the exposed dentin or vital pulp on the floor of deep cavities after removing deep caries or after exposure to trauma.[1] These protective biomaterials should have specific properties such as biocompatibility, biointeractivity (biologically relevant ions releasing), and bioactivity (apatite-forming ability) to activate the pulp cells and the formation of reparative dentin.[1]

Pulp capping on the exposed pulp act as a barrier, protect the dentin-pulp complex, and maintain its vitality.[1] Calcium hydroxide [Ca(OH)2] cements are the most suitable agents for direct and indirect pulp capping which have the ability to release hydroxyl (OH) and calcium (Ca) ions upon dissolution.[2],[3] Its alkaline pH (pH 9–11) stimulates the formation of secondary/reparative dentin in direct contact with the pulp.[2],[3]

Unfortunately, self-curing Ca(OH)2 cement (Dycal) is soluble, raises alkalinity, and forms a necrotic layer at the material–pulp interface and also it has greater chances of microleakage. Pulp capped with lack of tight restoration showed inflammatory response in pulp tissues and became necrotic.[4] The success of pulp capping agents relies on the ability of Ca(OH)2 to disinfect the superficial pulp and dentin. The qualified bacteria-free or bacteria tight seal provided by the restoration is a very important factor in successful pulp capping. Recontamination through microleakage of restoration increases the failure of the procedure.[5]

The “tunnel defects” in the reparative dentin is the critics of Ca(OH)2 and it is formed under the Ca(OH)2 pulp capping.[6] A tunnel defect is described as a patency from the area of the exposure through the reparative dentin to the pulp, sometimes which involves fibroblasts and capillaries situated within this defect.[7] However, other researchers have found that the quality of reparative dentinal bridge improves as it gets thicker in which mostly the tunnel defects are not patent with the pulp.[8]

Another disadvantage of Ca(OH)2 cements for pulp capping is the setting in the presence of blood and other biological fluids. Hence, the possibility to light-cured pulp capping material is seemed to be advantageous for dental practitioners. Beside this, there are some recent light-cured Ca(OH)2 cements which have tricalcium silicate particles from which Ca ions are released. It is important to measure Ca ions from these new materials. Hence, the aim of this study is to compare Ca ion-releasing capacity of two different light-cured Ca(OH)2 cements (Septocal and TheraCal) with self-cured Ca(OH)2 cements (Dycal).

  Materials and Methods Top

Five different brands of Ca(OH)2 cements were taken [Table 1] and they were divided into five groups which are as follows: Group I - Dycal (control group), Group II - Septocal, Group III – TheraCal, Group IV - Cal LC, and Group V – Hydrocal [Table 1]. All specimens (n = 50) were prepared by mixing and curing the cements according to manufacturer's instructions. Ten samples of Group I (Dycal) were manipulated by mixing it according to manufacturer's instructions. Then, ten samples of the remaining groups were manipulated by curing the cements with light emitting diode (LED) according to their manufacturer's instructions. The different cement pastes were placed into the plastic molds (3 mm in diameter and 1.5 mm height). The pellet with the 1.5 mm height and 3 mm diameter was prepared. The exposed surface area of each sample was approximately 14 mm 2. Each filled mold was placed on the bottom of 4 cm high test tube which is filled with 10 ml of deionized water at 37°C. The stored water was collected for Ca analysis and replaced after 7, 14, and 21 days. Thus, ion releases were measured after 7, 14, and 21 days by Inductively coupled plasma optical emission spectroscopy test (Prodigy Company). For Ca quantization, 0.1 ml HNO3 was added to 10 ml (deionized) water to create a simulated intrapulpal pressure equivalent to 3 cm H2O which was recorded when the data had stabilized to the second decimal place.
Table 1: Different groups of the study

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  Results Top

Ca ion release from all groups at various time durations was measured [Table 2] and mean was calculated with the standard deviation also [Table 3]. The values are shown in [Table 2] and [Table 3]. These values are compared using two-way ANOVA and Tukey's post hoc test which showed highly significant result with P < 0.001.
Table 2: Calcium ion release from different calcium hydroxide cements

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Table 3: Means of calcium ion release with standard deviation

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  Discussion Top

In 1930, Ca(OH)2 put forward as a “remineralizing agent” in pulp capping played an important role in the reparative dentinogenesis in proximity to pulp tissues due to the release of Ca and OH ions. This Ca gradient activates the proliferation of undifferentiated cells from the pulp and activates stem cells also. The alkaline pH creates unfavorable conditions for any remaining organism and exerts an antibacterial/bacteriostatic action, increasing the expression of alkaline phosphatase and bone morphogenic protein-2 (BMP-2) and promoting the formation of calcified nodules.

Ca ions help in the differentiation and mineralization of pulp cells.[9] The released Ca ions increase the proliferation of human dental pulp cells which is dependent on the dose.[10],[11],[12] In addition, Ca ions modulate osteopontin and BMP-2 levels during the pulp calcification,[13] and the release of Ca also enhances the activity of pyrophosphatase which maintains dentin mineralization and forms a dentin bridge.[14] Thus, continuous release of Ca ions from a pulp capping material is the main reason for the proliferation and differentiation of human dental pulp cells.

Ca neutralizes lactic acid released from osteoclasts which prevents dissolution of mineral components from dentin. It also inactivates the lipopolysaccharide endotoxin which causes inflammation by acting on macrophages and induces the periapical pathosis [15] and osteoclastogenesis. Superficial coagulation of dental pulp is caused by damage to blood vessels. This coagulation necrosis helps in the differentiation of odontoblasts and elaborates the matrix. Ca ions also reduce the permeability of new capillaries to Ca. Thus, more Ca ions are retained in healing because source of Ca for reparative dentin formation is blood and the Ca from Ca(OH)2 cement is only the stimulating agent.

The Ca ions play a key role in the various biological events of the cells involved in the neoformation of mineralized hard dental tissues. Ca ion stimulates the expression of bone-associated proteins mediated by Ca channels,[16] and large quantities of Ca ions can activate adenosine triphosphate which plays a significant role in the mineralization process.[17] The released Ca ions increase the proliferation of human dental pulp cells which is dependent on the dose.[10],[11],[12] Ca-releasing materials accelerate odontoblast differentiation: 2–4 mmol/L (80–160 ppm) concentration of Ca ions stimulates the osteoblasts, while 6–8 mmol/L induces differentiation and >10 mmol/L shows the cytotoxic effect.[18] It was considered normal extracellular Ca concentration as approximately 2–6 mmol/L.[11]

Ca ion release from Dycal occurred during the 21-day period is in agreement with other studies,[19] and TheraCal released significantly more Ca ions than Dycal in the experimental period which is similar with the other studies.[20] However, the findings of Ca release cannot be comparable because the experimental protocols are different. Hydrocal which is newly added material in this study also shows significant ion release compared to TheraCal. Interestingly in this study, the bulk of Ca ions released from Hydrocal and TheraCal is above 4 mmol/L which can have the potential to stimulate the activity for dental pulp cell and odontoblasts.[19],[21] The results of this study showed that the resin portion in the light-cured Ca(OH)2 cement (containing hydrophobic and hydrophilic monomers) can promote Ca and OH ion release within the wet area on the tooth pulp and/or dentin and favored the interaction with the hydrophilic tooth dentin.[22] The results of the water absorption test of one study showed that the hydrophilic resin in TheraCal allows some water absorption which is responsible for the hydration reaction of the Portland cement particles with the formation of Ca(OH)2.[22] The occurrence of similar chemical and physical events in a light-cured material was recently reported.[22]

The present study proved that Ca and OH ion release from the pulp capping materials supposed to be continue over time and the action of these on vital tissue can induce the deposition of hard tissue.[23] The chemical dissociation occurs in the presence of fluids and the Ca and OH ions dissociated from Ca(OH)2 can penetrate the surrounding dentinal tubules.[23] Clinically, it is possible to evaluate that a wet condition may maintain the dissociation constant because of the presence of fluid.[23]

One of the main limitations of the self-cure Ca(OH)2 cements is high solubility within 1–2 years after application in tissue fluids which leads to the disappearance of the material and the formation of tunnel defects in reparative dentin under the capping, therefore failing to provide a permanent seal against bacterial entry.[4],[24] Unluckily, there is a lack of international standards and test methods for both conventional and light-cured Ca(OH)2 cements. This deficiency has been also mentioned by others.[25] Therefore, standard requirement for these materials is strongly needed as stated in other studies.

Some modifications to ISO 6876 methodology [26],[27] have been introduced because there are different types of the test materials. In this study, the internal diameter of the mold (3 mm) was less than the diameter of the LED light tip (15 mm) for the purpose of exposing all the sample surfaces. TheraCal sets after 20 s of light curing up to a depth of approximately 2 mm to achieve its better physical properties.

Ca(OH)2 affects pulp repair by many mechanisms of action. It has antibacterial properties which can minimize or remove bacterial penetration into the pulp.[28] Traditionally, it has been believed that Ca(OH)2 alkalinity irritates the pulp tissue stimulating repair through some unknown mechanism.[29] Nowadays, the “unknown mechanism” is the release of bioactive molecules. It is known that different types of proteins are involved in the dentin matrix during dentinogenesis. Particularly, two of them, BMP and transforming growth factor beta one have the ability to stimulate pulp repair.[30] In addition, Ca(OH)2 solubilize these proteins from dentin which leads to the release of the bioactive molecules as a mediator in pulp repairing process.[31],[32]

Ion release depends on the nature of the particles. The network structure of the cement is responsible for water sorption and solubility as well as the permeability of the material to water diffusion (i.e., porosity). With the exception of conventional Ca(OH)2 formulations that underwent rapid and complete solubilization, the present study showed that light-cured Ca(OH)2 cements released more free Ca ions than conventional self-cured Ca(OH)2 cements. The high amount of Ca release can be associated with the presence of a Ca silicate component and low solubility (11.83%) related with the presence of superplasticizer which is commonly used to reduce the water requirement (L/P 0.257). Due to which, it disperses the particles and enhances the fluidity leading to make the cement self-consolidating. In addition, the faster hydration reaction of tricalcium silicate particles in the light-cured Ca(OH)2 cements can be associated with the low solubility and high Ca release during the early few hours. The large amount of released Ca ions facilitates the formation of Ca phosphate deposits. Due to its favorable biological properties such as biocompatibility, osteoconductivity, bioresorption, and biomineralization, Ca carbonate activates the cells in mineralization.

TheraCal (Bisco Inc., Schaumburg, IL, USA) is likely related to the presence of a light-curable resin and the ability to release a moderate but rather constant amount of Calcium ions in agreement with Gandolfi et al.[20] The material's considerable bioactivity is connected with the presence of silanol groups and resin groups that are able to promote the formation of Ca phosphate deposits. In this study, light-cured Ca(OH)2 materials showed high biointeractivity (ion release) and bioactivity with high open pore volume (i.e., porosity). The internal network of high open pore volume provides a large surface area for the leaching process.[20]

Mineralized tissue formation due to contact of Ca(OH)2 and connective tissue has been observed from 7th to 10th day after application.[31] The complete antibacterial activity takes place in 7 days by Ca(OH)2, and the slight inflammation induced by Ca(OH)2 is resolved in 14 days.[26] Even though the recommended application period for the Ca(OH)2 is 4–5 weeks, it is reported that 4–5 weeks of Ca(OH)2 application causes necrosis of the normal cells. Hence, it has been chosen as 7, 14, and 21 days for Ca ion release measurement in this study.

In the present study, a simulated intrapulpal pressure of 0.29 KPa produced by the water in the cylindrical containers was used. Normal intrapulpal pressure is 1.5 KPa (15 cm H2O) and of inflamed pulp is 3.5 KPa (36 cm H2O). A low intrapulpal pressure favors the movement of ions through the dentinal tubules to the pulp, while the ionic dissociation from the materials is certainly reduced.

All the materials tested in this study are proved to be Ca ion releasing. Light-cured Ca(OH)2 cements proved to release Ca for a period of up to 21 days significantly and it released significantly more Ca than Dycal during all the test periods.

Thus, in addition, the resin particles in the dentin-pulp complex and in the pulp seemed to trigger foreign body reaction in stimulating the inflammatory mononuclear infiltrate as well as the multinuclear giant cells as stated by Gwinnett and Tay,[32] and the unresolved inflammation is associated with the disturbance in the reparative dentin bridge formation.[4]

  Conclusions Top

Within the limitation of the present study, all light-cured Ca(OH)2 cements released high amount of Ca ions compared to self-cured Ca(OH)2 cements. Hydrocal and TheraCal were found to be the highest Ca ion-releasing materials among them.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Table 1], [Table 2], [Table 3]

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