The influence of pH and lactic acid concentration on the formation of artificial root caries in acid buffer solution

Hyun-Suk Oh; Byoung-Duck Roh; Chan-Young Lee

doi:10.5395/JKACD.2007.32.1.047

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Oh, Roh, and Lee: The influence of pH and lactic acid concentration on the formation of artificial root caries in acid buffer solution

Original Article

Journal of Korean Academy of Conservative Dentistry

Journal of Korean Academy of Conservative Dentistry 2007; 32(1): 47-60.

Published online: 31 January 2007

DOI: https://doi.org/10.5395/JKACD.2007.32.1.047

The influence of pH and lactic acid concentration on the formation of artificial root caries in acid buffer solution

Hyun-Suk Oh, Byoung-Duck Roh, Chan-Young Lee

Department of Conservative Dentistry, College of Dentistry, Yonsei University, Korea.

Corresponding Author: Chan-Young Lee. Department of Conservative Dentistry, College of Dentistry, Yonsei University, 134 Shinchon-Dong, Seodaemun-Ku, Seoul, Korea, 120-752. Tel: 82-2-2228-8700, Fax: 82-2-313-7575, chanyoungl@yumc.yonsei.ac.kr

Received 26 October 2006 Revised 4 December 2006 Accepted 9 January 2007

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The purpose of this study is to compare and to evaluate the effect of pH and lactic acid concentration on the progression of artificial root caries lesion using polarizing microscope, and to evaluate the morphological changes of hydroxyapatite crystals of the demineralized area and to investigate the process of demineralization using scanning electron microscope.

Artificial root caries lesion was created by dividing specimens into 3 pH groups (pH 4.3, 5.0, 5.5), and each pH group was divided into 3 lactic acid concentration groups (25 mM, 50 mM, 100 mM). Each group was immersed in acid buffer solution for 5 days and examined. The results were as follows:

1. Under polarized microscope, the depth of lesion was more effected by the lactic acid concentration rather than the pH.

2. Under scanning electron microscope, dissolution of hydroxyapatite crystals were increased as the lactic acid concentration increased and the pH decreased.

3. Demineralized hydroxyapatite crystals showed peripheral dissolution and decreased size and number within cluster of hydroxyapatite crystals and widening of intercluster and intercrystal spaces as the pH decreased and the lactic acid concentration increased.

4. Under scanning electron microscope evaluation of the surface zone, clusters of hydroxyapatite crystals were dissolved, and dissolution and reattachment of crystals on the surface of collagen fibrils were observed as the lactic acid concentration increased.

5. Under scanning electron microscope, demineralization of dentin occurred not only independently but also with remineralization simultaneously.

In conclusion, the study showed that pH and lactic acid concentration influenced the rate of progression of the lesion in artificial root caries. Demineralization process was progressed from the surface of the cluster of hydroxyapatite crystals and the morphology of hydroxyapatite crystals changed from round or elliptical shape into irregular shape as time elapsed.

Keywords: Root caries, Acid buffer solution, pH, Lactic acid concentration, Demineralization, Hydroxyapatite, Scanning electron microscope

Figures and Tables

Figure 1

Polarizing microscopic view of demineralized dentin of group pH 4.3 in acid buffer solution (5 day treatment, × 100, imbibed in water).

Figure 2

Polarizing microscopic view of demineralized dentin of group pH 5.0 in acid buffer solution (5 day treatment, × 100, imbibed in water).

Figure 3

Polarizing microscopic view of demineralized dentin of group pH 5.5 in acid buffer solution (5 day treatment, × 100, imbibed in water).

Figure 4

The effect of the pH and lactic acid concentration in buffer solution on the progression of artificial root caries (µm).

Figure 5

SEM image of demineralized pattern in root dentin (pH 4.3-Lactic acid 100mM).

Figure 6

SEM images of demineralized dentin of pH 4.3-Lactic acid 100 mM (zone A - zone F).

Figure 7

SEM images of demineralized dentin of peritubular dentin (× 50,000).

Figure 8

SEM images of demineralized dentin of intertubular dentin (× 100,000).

Table 1

The composition of initial demineralization solution of group pH 4.3

Table 2

The composition of initial demineralization solution of group pH 5.0

Table 3

The composition of initial demineralization solution of group pH 5.5

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