Caries activity assessment using the micro pH sensor and Real time PCR for cariogenic organisms obtained from the lowest pH area of caries dentin

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The aim of this clinical study, was to measure the surface pH of carious dentin using the micro pH sensor directly. 25 samples obtained from 20 patients (mean age: 53.8) were classified into active or arrested carious dentin before the pH assessments. If sample was not classified both type of carious dentin, it was recognized pre-active carious dentin. The surface pH of intact enamel was also measured using this micro pH sensor. Moreover, saliva, plaque and carious dentin samples were obtained from same subjects to evaluate carious organism's populations using Real time PCR methods. The surface pH was range from pH 3.8 to pH 5.2 for active carious dentin, range from pH 5.8 to pH 6.3 for arrested carious dentin, and pH 5.4 for pre-active carious dentin respectively. There were statistical differences on the surface pH value between active and arrested carious dentin, and pre-active and arrested carious dentin (p<0.05). On the other hand, the surface pH values after caries removing was about pH 6.4 for all types of carious dentin. Because the critical pH of the crystal of carious affected dentin is pH 6.4, that pH value after carious removing might show the inner layer of carious dentin. From the results of pH analysis, this micro pH sensor could be useful for clinical assessments for the carious activity. Although the genomic DNA of S. mutans was detected all carious samples, there was not statistical differences on the rate of genomic DNA for the S. mutans between active and arrested carious dentin. There were non detected samples for the genomic DNA of S. sobrinus among active carious dentin. The rate of genomic DNA of S. sobrinus related to the active carious dentin was lower than that of arrested carious dentin.