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ORIGINAL ARTICLE
Year : 2006  |  Volume : 24  |  Issue : 3  |  Page : 144-145
 

An in vitro evaluation of pH variations in calcium hydroxide liners


Department of Pedodontics and Preventive Dentistry, The Oxford Dental College, Hospital and Research Centre, Bangalore, Karnataka, India

Correspondence Address:
P Subramaniam
Department of Pedodontics and Preventive Dentistry, Oxford Dental College, Hospital and Research Center, 10th Mile, Hosur Road, Bommanahalli, Bangalore - 560 068, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-4388.27895

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   Abstract 

The purpose of this present study was to determine the pH changes of five different commercially available calcium hydroxide liners and variations of pH at different time intervals. The following commercially available materials were investigated: Dycal (LD Caulk); Calcimol (Vocco Products); calcium hydroxide powder (Deepti Products); Calcimol LC (Vocco Products); Lime-Lite (Pulpdent Corporation). Five samples were prepared from each liner. The pH measurements were recorded at time intervals of 1 h, 24 h, 3 days and 7 days after mixing of the liner. The pH variations of each material at the given time intervals were recorded and the means were calculated. Comparison of the mean values at all time intervals with the statistical analysis showed significantly high differences ( P < 0.001) between pH values induced by each material at all time intervals. Among the water-insoluble products, Dycal had the strongest alkaline effect after 7 days interval. The materials that chemically hardened produced higher pH values than materials that hardened by a visible light source after 7 days.


Keywords: Calcium hydroxide, liner, pH


How to cite this article:
Subramaniam P, Konde S, Prashanth P. An in vitro evaluation of pH variations in calcium hydroxide liners. J Indian Soc Pedod Prev Dent 2006;24:144-5

How to cite this URL:
Subramaniam P, Konde S, Prashanth P. An in vitro evaluation of pH variations in calcium hydroxide liners. J Indian Soc Pedod Prev Dent [serial online] 2006 [cited 2020 Jun 3];24:144-5. Available from: http://www.jisppd.com/text.asp?2006/24/3/144/27895



   Introduction Top


Cavity liner is defined as a liquid in which calcium hydroxide is suspended in solution of natural or synthetic resins.[1] The main purpose of cavity liners is to use the beneficial effects of calcium hydroxide in accelerating the formation of reparative dentin and the high pH resulting in unfavorable conditions for possible remaining organisms.[2]

A layer of cavity liner is placed on the floor of the cavity to protect the pulp from chemical irritants of the restorative material, sterilization of the remaining soft dentin and also to promote reparative dentin formation by increasing the pH of the underlying dentin. It also reduces the permeability of dentin.[1]

The therapeutic effects of calcium hydroxide liners are dependent on the dissociation of calcium hydroxide into calcium and hydroxide ions. This causes high alkalinity, which would activate adenosine triphosphate activity, which in turn might accelerate the mineralization of hard tissues like dentin and bone. The presence of calcium and hydroxide ions might modify the environmental pH in areas of inflammation to levels favorable for cell division and matrix mineralization.[3],[4]

The purpose of this study was to determine the pH changes of five different commercially available calcium hydroxide liners and variations of pH at different time intervals.


   Materials and Methods Top


The following commercially available materials were investigated: Dycal (LD Caulk); Calcimol (Vocco Products, Germany); calcium hydroxide powder (Deepti Products, India); Calcimol LC (Vocco Products, Germany); Lime-Lite (Pulpdent Corporation). Each product was mixed in accordance with manufacturer's instructions, allowed to set in plastic moulds (diameter 3.5 mm, height 2 mm) and pressed between two glass microscopic slides. Five samples were prepared from each liner. The samples of Dycal, calcium hydroxide powder and Calcimol materials were allowed to harden chemically at 26C and Calcimol LC and Lime-Lite samples were allowed to harden by means of a visible light curing source (LA 500 Blue Light, Apaza Enterprise) for 40 s. The resultant samples were taken out of the moulds and placed into separate vials, each containing 10 ml de-ionized water (starting pH 7.0). The samples were stored at room temperature (26-27C) and pH measurements were recorded at time intervals of 1 h, 24 h, 3 days and 7 days after mixing of the liner. An Ultrameter Digital pH meter (Myroll Company, USA), which was calibrated with standard buffer solutions and a glass electrode connected to the pH meter (Myroll, USA) were used for the measurements.

Statistical analysis was done using ANOVA and post-hoc of Tukey test for the mean pH values recorded.


   Results Top


Mean pH values and standard deviations of the test materials are shown in the [Table - 1]. Comparison of the mean values at all time intervals with the above analysis showed significantly high differences ( P < 0.001). The pH values of calcium hydroxide powder were significantly high at all intervals of time. At 1 h, the calcium hydroxide powder group showed the highest pH level, while Calcimol LC showed the lowest pH levels. At 24 h also, calcium hydroxide powder showed the highest pH levels, whereas Calcimol LC showed the lowest pH levels. At 3 days and 7 days, calcium hydroxide powder showed the highest pH levels, whereas Calcimol LC showed the lowest pH levels.

Among the water-insoluble products, Calcimol showed the highest pH values at the 1-hour interval, Lime-Lite showed the highest pH values at 24 h and Dycal had the strongest alkaline effect at the 3- and 7-day intervals.


   Discussion Top


The calcium hydroxide preparations stimulate the formation of a calcified bridge in the area of pulp exposure.[1],[5] The therapeutic effects of calcium hydroxide liners are dependent on the dissociation of calcium hydroxide into calcium and hydroxide ions. This causes high alkalinity, which would activate adenosine triphosphate activity, which in turn might accelerate the mineralization of hard tissues like dentin and bone. The presence of calcium and hydroxide ions might modify the environmental pH in areas of inflammation to levels favorable for cell division and matrix mineralization. Because of high pH, calcium hydroxide helps to keep the immediate region in a state of alkalinity, which is necessary for bone and dentin formation. Under the region of calcium hydroxide layer, there is a superficial layer of calcium hydroxide induced coagulative necrosis; cells from the underlying pulp tissue differentiate into odontoblasts, which produce the reparative dentin.[5],[6],[7]

Some investigators like Van Hassel believe that in an alkaline pH environment, the enzyme phosphatase liberates inorganic phosphate from the blood, which later precipitates as calcium phosphate.[8] Also, it is noted that bacteria like streptococci and staphylococci can grow only in a pH between 3 and 8, but the pH under calcium hydroxide liner is above 10, which results in bactericidal effect of calcium hydroxide.[8] Also, dissociation of calcium hydroxide present in different commercial products is an essential condition to maintain a high alkaline environment improper for bacterial survival.[9] In the present study, all tested liners were able to alkalinize de-ionized water at the test intervals. The results showed that calcium hydroxide powder had the highest pH values at all intervals of time. The ideal product should allow a gradual and slow release of calcium and hydroxyl ions.[10] Calcium hydroxide powder and Dycal showed a slow rise in pH over a period of time, favoring the effect of calcium hydroxide pH on the pulp.

In an in vivo situation, there is a continuous exchange of tissue fluids at the medicament interface that will rapidly dilute the effect of the calcium hydroxide pH.[2],[11] Hence, further clinical-based studies are warranted. In the present study, the pH values of calcium hydroxide liners were statistically different at different time intervals. Calcium hydroxide powder showed the highest pH at all intervals. All the calcium hydroxide liners rendered de-ionized water alkaline. The materials that chemically hardened produced higher pH values than materials that hardened by visible light source after 7 days.

 
   References Top

1.Phillips RW. Science of dental materials, 9th ed. Prism Books Pvt Ltd: 1992.  Back to cited text no. 1    
2.Abbasi J, Rahmat AB. The pH variation in calcium hydroxide liners. Quintessence Int 1987;18:225-6.  Back to cited text no. 2    
3.Simon ST, Bhat KS, Francis R. Effect of four vehicles on the pH of calcium hydroxide and the release of calcium ion. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1995;80:459-64.  Back to cited text no. 3  [PUBMED]  
4.Torneck CD, Moe H, Howley TP. The effect of cacium hydroxide solution on procaine pulp fibroblasts in vitro. J Endod 1983;9: 131-6.  Back to cited text no. 4  [PUBMED]  
5.Abiko Y. Studies on calcium stimulated adenosine triohosphatase in the albino rabbit dental pulpitis subcellular distribution and properties. J Dent Res 1977;56:1558-68.  Back to cited text no. 5  [PUBMED]  
6.Tronstad L, Andreasen JO, Hasselgren G, Kristerson L, Riis I. pH changes in dental tissues after root canal filling with calcium hydroxide. J Endod 1980;7:17-21.  Back to cited text no. 6    
7.Guo MK, Messer HH. Properties of CA- activated adenosine triphosphatase from rat incisor pulp. Arch Oral Biol 1976;21: 637-40.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Basrani E. Fractures of the teeth. Lea and Febiger Pub: 1985.  Back to cited text no. 8    
9.Staehle HJ, Spiess V, Heinecke A, Muller HP. Effect of root canal filling materials containing calcium hydroxide on the alkalinity of root dentin. Endod Dent Traumatol 1995;11:163-8.  Back to cited text no. 9  [PUBMED]  
10.de Andrade Ferreira FB, Silva E Souza PA, do Vale MS, de Moraes IG, Granjeiro JM. Evaluation of pH levels and calcium ion release in various calcium hydroxide endodontic dressings. Oral Surg Oral Med Oral Pathol oral Radiol Endod 2004;97:388-92.  Back to cited text no. 10    
11.Gencay K, Seymen F, Selvi S, Kiziltan B. In vitro evaluation of pH changes induced by calcium hydroxide liners. Quintessence Int 2004;35:560-2.  Back to cited text no. 11  [PUBMED]  


    Tables

[Table - 1]


This article has been cited by
1 Bacteriology of deep carious lesions underneath amalgam restorations with different pulp-capping materials - An in vivo analysis
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2 Incorporation of anti-inflammatory agent into calcium hydroxide pulp capping material: An in vitro study of physical and mechanical properties
Louwakul, P. and Lertchirakarn, V.
Dental Materials Journal. 2012; 31(1): 32-39
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    Abstract
    Introduction
    Materials and Me...
    Results
    Discussion
    References
    Article Tables

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