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KMID : 0355420100340010009
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Journal of Korean Academy of Oral Health
2010 Volume.34 No. 1 p.9 ~ p.17
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Development of a new color scale for a caries activity test
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Kang Si-Mook
Kim Baek-Il
Kwon Ho-Keun
Jeong Seung-Hwa
Jung Hoi-In
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Abstract
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Objectives: The aim of this study was to develop a new caries activity test based on colorimetric changes that could better reflect the amount of acid produced by oral bacteria as a broad spectrum of color than the previous test. The optimal candidates were combinations of pH indicators, and these were evaluated in pH buffering solutions and using dental plaque.
Methods: Six pH indicators, Bromocresol-purple (BCP), Bromocresol-green (BCG), Methyl-red (MR), Methyl-orange (MO), Resazurin (R), and Naphthyl-red (NR), were selected to show different colors at various pH environments (range pH 3.0∼7.0). BCP and BCG are pH indicators that are already used in the Cariostatⓡ, and they can show color changes from blue to yellow. This study tried to broaden the color change spectrum from blue to red to give a more distinct differentiation at various pHs. Four pH indicators (MR, MO, R and NR) were blended with BCP and BCG. Each combination of the three indicators was assessed in different pH buffer systems: pH 7.0, 6.0, 5.0, 4.0, and 3.0. The selected combinations of pH indicators were applied to human dental plaque from 11 subjects (mean age: 27) to confirm the reproducibility of the in vitro results.
Results: According to the in vitro buffer system, the mixture of BCP, BCG and MR did not show any differences between pH 4.0 and pH 3.0. On the other hand, the mixtures of BCP-BCG-MO (ratio 2：1：1.5), BCP-BCG-R (1.5：1：0.5) and BCP-BCG-NR (2：1：1.5) showed distinguishable color changes from pH 7.0 to pH 3.0. Among the three candidates, the BCP-BCG-NR mixture showed the best color differences in the buffer solution and the human dental plaque cultivated solutions at various pHs.
Conclusions: This study evaluated a new colorimetric caries activity test that used a combination of several pH indicators. The new system can easily detect various pH environments from organic acid fermentation by using a wider range of colors (blue ? dark green ? green ? orange ? red).
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KEYWORD
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caries, caries activity test, cariogenic bacteria, cariostat, pH indicator
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