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

本临床研究的目的是利用微型pH传感器直接测量龋牙本质表面的pH值。从20例患者（平均年龄：53.8岁）中获得25份样本，在进行pH评估前将其分为活性牙本质或停牙本质。如果样品未被分类为两种类型的牙本质，则识别为预活动性牙本质。用该微pH传感器测量了完整牙釉质的表面pH值。同时，采集同一受试者的唾液、牙菌斑和龋牙本质样本，采用Real - time PCR方法评估龋菌种群。活性牙本质表面pH值为pH 3.8 ~ pH 5.2，抑制牙本质表面pH值为pH 5.8 ~ pH 6.3，预活性牙本质表面pH值为pH 5.4。活性牙本质与滞留牙本质、预活性牙本质与滞留牙本质表面pH值比较，差异均有统计学意义（p<0.05）。各类型龋牙本质除龋后表面pH值均在6.4左右。由于龋病牙本质结晶的临界pH值为pH 6.4，因此该pH值可显示龋病牙本质的内层。从pH分析结果来看，该微pH传感器可用于临床评估龋活性。虽然在所有龋样品中都检测到变形链球菌的基因组DNA，但在活性牙本质和抑制牙本质之间，变形链球菌的基因组DNA率没有统计学差异。在活性龋牙本质中，未检测到sobrinus的基因组DNA。与活性牙本质相关的基因组DNA率低于与抑制牙本质相关的基因组DNA率。

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.