Restor Dent Endod.  2016 Feb;41(1):12-21. 10.5395/rde.2016.41.1.12.

Effect of acidic solutions on the microhardness of dentin and set OrthoMTA and their cytotoxicity on murine macrophage

• Oh S
• Perinpanayagam H
• Lee Y
• Kum JW
• Yoo YJ
• Lim SM
• Chang SW
• Shon WJ
• Lee W
• Baek SH
• Kum KY

• KMID: 2316959
• DOI: http://doi.org/10.5395/rde.2016.41.1.12

Abstract

OBJECTIVES
To evaluate the effects of three acids on the microhardness of set mineral trioxide aggregate (MTA) and root dentin, and cytotoxicity on murine macrophage.
MATERIALS AND METHODS
OrthoMTA (BioMTA) was mixed and packed into the human root dentin blocks of 1.5 mm diameter and 5 mm height. Four groups, each of ten roots, were exposed to 10% citric acid (CA), 5% glycolic acid (GA), 17% ethylenediaminetetraacetic acid (EDTA), and saline for five minutes after setting of the OrthoMTA. Vickers surface microhardness of set MTA and dentin was measured before and after exposure to solutions, and compared between groups using one-way ANOVA with Tukey test. The microhardness value of each group was analyzed using student t test. Acid-treated OrthoMTA and dentin was examined by scanning electron microscope (SEM). Cell viability of tested solutions was assessed using WST-8 assay and murine macrophage.
RESULTS
Three test solutions reduced microhardness of dentin. 17% EDTA demonstrated severe dentinal erosion, significantly reduced the dentinal microhardness compared to 10% CA (p = 0.034) or 5% GA (p = 0.006). 10% CA or 5% GA significantly reduced the surface microhardness of set MTA compared to 17% EDTA and saline (p < 0.001). Acid-treated OrthoMTA demonstrated microporous structure with destruction of globular crystal. EDTA exhibited significantly more cellular toxicity than the other acidic solutions at diluted concentrations (0.2, 0.5, 1.0%).
CONCLUSIONS
Tested acidic solutions reduced microhardness of root dentin. Five minute's application of 10% CA and 5% GA significantly reduced the microhardness of set OrthoMTA with lower cellular cytotoxicity compared to 17% EDTA.

Keyword

Citric acid; EDTA; Glycolic acid; OrthoMTA; SEM; Vickers surface microhardness

MeSH Terms

Cell Survival
Citric Acid
Dentin*
Edetic Acid
Humans
Macrophages*
Pemetrexed
Citric Acid
Edetic Acid

Figure

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  Figure 1 Mean Vickers microhardness values (N/mm2) of OrthoMTA, before and 5 minutes after exposure to four different solutions. *Indicates statistically significant change before and after exposure to each solution. Different uppercase letters indicate significant differences between four groups after application of test solutions (p < 0.05). EDTA, ethylenediaminetetraacetic acid.

• 

  Figure 2 Mean Vickers microhardness values (N/mm2) of dentin, before and 5 minutes after exposure to four different solutions. *Indicates statistically significant change before and after exposure to each solution. Different uppercase letters indicate significant differences between four groups after application of test solutions (p < 0.05). EDTA, ethylenediaminetetraacetic acid.

• 

  Figure 3 Scanning electron microscope photomicrographs showing dentinal tubules of the root canal walls treated with test solutions for five minutes. (a, b) saline treated dentin, no erosion is shown. (original magnification, (a) ×1,000, (b) ×20,000); (c, d) 17% EDTA treated dentin demonstrates severe erosion, and dentinal tubules are collapsed (original magnification, (c) ×1,000, (d) ×10,000); (e, f) 10% citric acid treated dentin shows erosion of dentin. Dentinal tubules are widened and collagens are collapsed (original magnification, (e) ×1,000, (f) ×10,000); (g, h) 5% glycolic acid treated dentin demonstrates little erosion. Dentinal tubules are widened but collagen fibrils are merely collapsed (original magnification, (g) ×1,000, (h) ×10,000). EDTA, ethylenediaminetetraacetic acid.

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  Figure 4 Scanning electron microscopic photographs of surface of the OrthoMTA exposed to test solutions for 5 minutes. (a - c) OrthoMTA exposed saline. Abundant cubic crystals are examined (original magnification, (a) ×500, (b) ×3,500, (c) ×15,000); (d - f) 10% citric acid exposed OrthoMTA. Cubic crystal is not seen. A few needle-like and laminated crystals with loss of matrix are identified. (original magnification, (d) ×500, (e) ×3,500, (f) ×15,000); (g - i) 5% glycolic acid exposed OrthoMTA. Microchannels are seen with loss of matrix. Cubic crystal is destructed. (original magnification, (g) ×500, (h) ×3,500, (i) ×15,000); (j - l) 17% EDTA exposed OrthoMTA. Cubic crystals are partially eroded (original magnification, (j) ×500, (k) ×3,500, (l) ×15,000). EDTA, ethylenediaminetetraacetic acid.

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  Figure 5 Effects of test solutions on the viability of RAW 264.7 cells. The viability of RAW 264.7 cells treated with various concentrations of test solutions for 24 hours was determined by WST-8 assay. Data represent the mean of triplicate experiments per condition and are expressed as a percentage of the control values. 17% EDTA was found to be more cytotoxic on cells than 10% citric acid, 5% glycolic acid, and saline at 0.2, 0.5, 1.0% dilutions. EDTA, ethylenediaminetetraacetic acid.

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