| Abstract|| |
Background: Calcium hydroxide [Ca(OH)2] is a material used during pulp capping treatment, despite being readily soluble in both water and acid. In contrast, propolis constitutes a nontoxic resin which is not easily dissolved in water. Therefore, a combination of Ca(OH)2and propolis is assumed to be capable of increasing the mechanical properties of Ca(OH)2and to diffuse into the dentinal tubules. Objective: This research aimed to reveal the solubility and water sorption ability of a combination of Ca(OH)2and propolis as pulp capping material. Materials and Method: The samples comprised 18 Ca(OH)2and Ca(OH)2-propolis chips, 15 mm × 1 mm in dimension, all of which were stored in an incubator for 24 h at 37°C. Each sample was then divided into two groups: one dissolved in 50 mL of artificial saliva for 24 h at 37°C and another for 7 days before being weighed, dried, incubated, and weighed for a second time. The result of the reduction in mass divided by the volume of the samples was considered to constitute the level of solubility and water sorption. The difference between the solubility and water sorption ability was analyzed using an independent t-test with significant difference <0.05. Results: The solubility of Ca(OH)2-propolis is lower than that of Ca(OH)2 after immersion for 1 day (P = 0.001) and 7 days (P = 0.000). The water sorption ability of Ca(OH)2-propolis is no different than that of Ca(OH)2after immersion for 1 day (P = 0.088) and 7 days (P = 0.635). However, the water sorption ability of Ca(OH)2-propolis after 1-day immersion is higher than immersion for 7 days (P = 0.012). Conclusion: The solubility Ca(OH)2-propolis is lower than that of Ca(OH)2, but its water sorption is higher than that of Ca(OH)2.
Keywords: Ca(OH)2, Ca(OH)2-propolis, solubility, water sorption
|How to cite this article:|
Pribadi N, Rosselle VR, Zubaidah N, Widjiastuti I. The solubility and water sorption properties of a combination of Ca(OH)2and propolis when used as pulp capping material. Indian J Dent Res 2020;31:557-61
|How to cite this URL:|
Pribadi N, Rosselle VR, Zubaidah N, Widjiastuti I. The solubility and water sorption properties of a combination of Ca(OH)2and propolis when used as pulp capping material. Indian J Dent Res [serial online] 2020 [cited 2020 Oct 31];31:557-61. Available from: https://www.ijdr.in/text.asp?2020/31/4/557/298407
| Introduction|| |
Pulp capping is the method of applying a layer of a more protective material to treat a caries- or trauma-induced pulp. The ingredient considered the gold standard for pulp capping is calcium hydroxide [Ca(OH)2] because of its ability to stimulate the formation of reparative dentine which protects the pulp from thermal stimulation and inhibits bacterial growth. Such inhibition is dependent upon the release of hydroxyl ions in an aqueous environment. Hydroxyl ions, highly oxidant free radicals that show extreme reactivity with several biomolecules, are able to bind to the phospholipid and cause membrane damage resulting in compromised integrity of the cytoplasmic membrane. The mechanical properties of Ca(OH)2 are deficient in terms of attachment to dentine because it is highly soluble while imperfect dentin bridge formation, referred to as “tunnel defects,” can cause microleakage resulting in bacteria being able to penetrate the dentinal tubules. The high solubility and water sorption of Ca(OH)2 may result in softening and inadequate sealing where the oral fluids can penetrate it partially or totally and cause it to dissolve. Due to the deficiencies of Ca(OH)2, researchers are actively seeking natural ingredients such as propolis that can serve as pulp capping materials.
Propolis is a resin substance derived from natural ingredients which is collected by bees and then mixed with wax and their saliva. Propolis does not affect pulp tissue and shows the ability to improve the mechanical properties of pulp capping material., Propolis contains bees wax [C13H27 CO2C26H53] and caffeic acid phenethyl ester (CAPE) [C9H8O4] which is nonpolar (hydrophobic), meaning that it is insoluble in water. The ability of CAPE [C9H8O4] to bind with Ca(OH)2 to form calcium salts underpins the expectation that a combination of Ca(OH)2 and propolis can improve the properties of Ca(OH)2.
The combination of Ca(OH)2 with propolis at a ratio of 1:2 used as pulp capping material in the form of a paste can enhance the ability of Ca(OH)2 to diffuse into dentinal tubules. One prerequisite of pulp capping material is that it insoluble in oral fluid. If solubility occurs, leakage will ensue resulting in tooth sensitivity and persistent pulp damage. Solubility is influenced by the strength of chemical bonds dependent upon the difference in electro negativity and the polarity of molecules. Solubility and water sorption represent important physical properties of pulp capping material. The solubility is determined by the characteristics of water sorption which constitute important factors in the physical properties of pulp capping material. After some time, possibly due to dissolution and water sorption, Ca(OH)2 proves incapable of remaining stable and evacuates the cavity. This study involved the use of Ca(OH)2-propolis at a ratio of 1:2 based on the assumption that the higher the relative atomic mass, the stronger the chemical bonds between the two materials. Based on the foregoing description of previous research, it is necessary to investigate the solubility and water sorption ability of Ca(OH)2-propolis compared to that of Ca(OH)2 since prior studies of pulp have not explained the role of capping material.
| Materials and Methods|| |
The research reported here constituted an experimental laboratory-based study with both pre and posttest control group design. Research samples consisted of propolis extract collected from subjects based in Lawang (East Java).
Propolis extract was prepared at Balai Penelitian dan Konsultasi Industri (BPKI), Surabaya, East Java, Indonesia by macerating up to 1 kg of dried Apis melifera honeycomb (100% propolis) sliced to a thickness of 0.5–1 cm. 1000 mL of 96% ethanol was subsequently added to the closed container and vibrated in an agitator at a speed of 80 rpm for 24 h to produce a homogeneous mixture which was then filtered. The residue was evaporated using an evaporator vacuum at a temperature of 50°C–60°C to separate the propolis extract from the ethanol in order to produce a thick liquid with a concentration of 11.45%. The 11.45% propolis extract was subsequently diluted using sterile distilled water until its concentration amounted to 11%.
Ca(OH)2 chips were produced by mixing pure Ca(OH)2 powder with sterile aquadest at a ratio of 1:1 (0.9 g Ca(OH)2 powder and 0.9 mL sterile aquadest), stirred using a cement spatula on a glass slab until its consistency became similar to that of paste and, finally, inserted into cylindrical molds (15 mm in diameter and 1 mm thick) (ISO 2009:4049). At the bottom of the mold, the sample was added to a celluloid strip and placed on a glass slab. After the sample mold had been filled with paste, a celluloid strip was applied to the upper part of the sample, pressed with a 1 cm thick glass slab, subjected to a 0.5 kg brass load and allowed to set. The hardened paste (setting) was then removed from the mold and the edge of the Ca(OH)2 chip trimmed with a sharp scalpel. In contrast, the combination of Ca(OH)2-propolis was produced by mixing Ca(OH)2 and propolis extract at a ratio of 1:2 (0.6 g Ca(OH)2 powder and 1.2 mL propolis extract) in the same manner as producing Ca(OH)2 chips (ISO 2009:4049). Thread was inserted into the middle of each sample with a sewing needle which also served as a handle during immersion. Each sample was placed in an incubator at 37°C for 24 h before being weighed with a precision scale (Mettler Toledo AL204 Analytical Balance). Measurement was repeated three times with the results being averaged in order to obtain a constant initial weight (called M1) (ISO 2009:4049).
Artificial saliva production
The artificial saliva used consisted of KCl (0.4 g/L), NaCl (0.4 g/L), CaCl2.2H2O (0.906 g/L), NaH2 PO4.2H2O (0.690 g/L), Na2S.9H2O (0.005 g/L), and urea (1 g/L) with pH 6.5. Plastic bottles filled with 50 mL of artificial saliva were then placed in an incubator at 37°C for 24 h.
Solubility and water sorption ability
Each sample was immersed in artificial saliva at a temperature of 37°C for 1 day and 7 days. The plastic bottle was then removed and the pieces extracted from the liquid without direct physical contact by means of holding the thread. Absorbent paper was used to absorb the artificial saliva from each sample before being weighed three times to obtain the average weight (referred to as M2). Each sample was subsequently incubated in an incubator at 37°C for 24 h and then weighed again to establish the constant weight (referred to as M3) (ISO 2009:4049).
The solubility of the material is established using the formula:
Solubility = (M1–M3)/V
where M1 is the sample weight prior to immersion, M3 is the sample weight after 1-day or 7-day immersion and subsequent incubation, and V represents the sample volume.
The water sorption of the material is calculated using the formula:
Water sorption = (M2–M1)/V
where M1 is the sample weight before immersion, M2 is the sample weight after 1-day or 7-day immersion, and V represents the sample volume.
The data obtained were tabulated for each group and analyzed for normality by means of a Kolmogorov–Smirnov test, whereas a Levene test was administered to measure the homogeneity of the data with a significance >0.05. Normally distributed and homogeneous data were examined using an independent t-test to reveal any significant differences between the groups with a significance <0.05.
| Results|| |
This research focused on the solubility and water sorption ability of Ca(OH)2-propolis combination as a pulp capping material compared to Ca(OH)2. The solubility of Ca(OH)2-propolis was lower than Ca(OH)2 in all groups. Ca(OH)2-propolis was significantly less soluble than Ca(OH)2 after immersion for 1 day (P = 0.001) and 7 days (P = 0.000) (P < 0.05). The solubility of Ca(OH)2-propolis after immersion for 7 days was lower than that for 1 day (P = 0.015) (P < 0.05) [Figure 1].
|Figure 1: The solubility of Ca(OH)2-propolis and Ca(OH)2 after immersion in artificial saliva. The character at the top of the bar indicates a difference for each group (P < 0.05)|
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The water absorption ability of Ca(OH)2-propolis was higher than Ca(OH)2 in all groups. There are no differences in water sorption ability between Ca(OH)2-propolis and Ca(OH)2 after immersion for 1 day (P = 0.088) and 7 days (P = 0.635) (P > 0.05). The water sorption of Ca(OH)2-propolis after immersion for 7 days was higher than that after immersion for 1 day (P = 0.012) (P < 0.05) [Figure 2].
|Figure 2: The water sorption ability of Ca(OH)2-propolis and Ca(OH)2 after being soaked in artificial saliva. The character at the top of the bar indicates a difference for each group (P < 0.05)|
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| Discussion|| |
The solubility of pulp capping material in oral fluid plays an important role in successful dental restoration. The resistance of a restoration to solubility can prevent the occurrence of microleakage, pulp irritation and secondary caries. One method used to measure solubility is that of immersing the material in a solution. The difference in material weight is the result of its solubility. Any material immersed in the solution will experience a different mechanism, namely absorption of water or water sorption (penetration of liquid molecules into the structure of the restoration material by diffusion) which causes an increase in mass and solubility (detachment of components from unreacted monomers) which causes a reduction in mass. Restoration material is regarded as effective if its solubility is close to zero, thereby enabling it to maintain the stability of the restoration when in contact with oral fluid.
This study used a sample in the form of chips of Ca(OH)2-propolis combination and Ca(OH)2. Propolis was selected on the basis of a range of criteria, namely; its nontoxicity to pulp tissue, nonpolarity, low solubility in water, together with its caffeic acid phenethyl ester, bees wax and volatile oil content.,, Ca(OH)2 chips were produced by mixing Ca(OH)2 powder and water at a ratio of 1:1 according to the factory rules, whereas the Ca(OH)2-propolis combination is made by mixing liquid Ca(OH)2 and 11% propolis powder at a ratio of 1:2., Each piece was 15 mm × 1 mm in dimension and underwent immersion for 1 day and 7 days at 37°C in accordance with ISO 4049 standards set by the International Standards Organization (2009). Artificial saliva was used as the soaking medium in this study with the aim of creating an analogous atmosphere to that in the oral cavity. Moreover, its mineral content was almost the same as that of the saliva present in the oral cavity. The study was conducted for 1 day in accordance with the assertion by Palin et al. (2015) that the solubility of the material increased within 24 h because nonreacted monomers were the main components released at an early stage in the process. However, another study by Palin et al. stated that the solubility of materials increases the greater the immersion time.
The solubility of Ca(OH)2-propolis is lower than Ca(OH)2. When immersed, a combination of Ca(OH)2 and propolis will break chemical bonds and cause the release Ca2+ ions from calcium acetylsalicylic salts [Ca (C9H7O4)2]. This salt is formed from the Ca(OH)2 and caffeic acid phenethyl ester [C9H8O4] contained in propolis,, Ionic bonds and hydrogen bonds occur between Ca(OH)2 and caffeic acid phenethyl ester [C9H8O4]. Ca2+ ions in ionic Ca(OH)2, together with C9H7O4- groups in propolis, produce calcium acetylsalicylic salts [Ca (C9H7O4)2] and OH- from Ca(OH)2 bonded H+ ions from propolis produce H2O., This condition renders the solubility of Ca(OH)2-propolis lower than Ca(OH)2.
The water sorption ability of Ca(OH)2-propolis after immersion for 7 days is higher than that after 1 day. The linear nature of solubility occurs when solubility is higher after 7 days compared to 1 day. Water sorption ability has a direct effect on solubility. The materials with low water sorption show low solubility. Water uptake is a key factor in the setting mechanism of pulp capping. The expansion caused by water diffusion induces the swelling of components in the spaces occupied by water, explaining the subsequent high water sorption observed in this material. When compared, the water sorption ability of Ca(OH)2-propolis is higher than that of Ca(OH)2, whereas the solubility of Ca(OH)2-propolis is lower than that of Ca(OH)2. These differences are attributable to the chemical bonds contained in the combination of Ca(OH)2-propolis, which consist of complex chemical bonds such as ionic, hydrogen, and Van der Waals forces, being stronger than the chemical bonds in Ca(OH)2 which contain only hydrogen and Van der Waals forces. This assertion is in accordance with the statement made by Carrero-Carralero et al. in their research regarding the solubility of carbohydrates in organic solvents that the strength of chemical bonds is influenced by relative atomic mass. In other words, the greater the relative atomic mass, the stronger the chemical bonds that occur and the lower the solubility.
The difference in solubility might be related to the contrasting chemical and surface composition of these materials. During hydration and setting of materials, the soluble calcium salts and Ca(OH)2 formed are rapidly washed out by water, which is indicated by the release of Ca ions from these materials, and their subsequent apatite forming ability. Another reason is the strength of the chemical bonds, including ionic bonds, hydrogen bonds and Van der Waals bonds, that occur in the combination of Ca(OH)2-propolis. Ionic bonds are ones that occur between two molecules possessing different ionic charges and represent the strongest of the three types of bonds. Propolis which contains various kinds of compounds, induces a strong chemical bond, while also containing CAPE and Bees Wax, two nonpolar substances which are not readily soluble in water.
The results of this study revealed two characteristics of Ca(OH)2-propolis, first; its ability to absorb high water, rendering the setting easier to achieve and, second; its low solubility that can be protracted in the oral cavity. The other experiment is required to confirm the other parameter for confirming that Ca(OH)2-propolis represents an ideal candidate for a pulp capping material.
| Conclusion|| |
The solubility Ca(OH)2-propolis is lower than that of Ca(OH)2, whereas its water sorption is higher than Ca(OH)2.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Nirawati Pribadi
Department of Conservative Dentistry, Faculty of Dental Medicine, Universitas Airlangga, Jl. Mayjend Prof. Dr. Moestopo 48, Surabaya 60132
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]