Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Caries Res. 2017;51(2):160-166. doi: 10.1159/000454781. Epub 2017 Feb 2.
Evaluating the physiochemical processes at the tooth surface/bacteria interface is important for elucidating the etiology of dental caries. This study aimed to compare the mineral solubility and protein degradation of coronal enamel (CE) and root dentin (RD), and investigate the involvement of dissolved components in bacteria-induced pH changes using a model of tooth/bacteria interface. An experimental apparatus forming a well was made of polymethyl methacrylate, and a bovine tooth (CE or RD) specimen was fixed at the bottom of the well. A miniature pH electrode was placed on the tooth, and Streptococcus mutans NCTC 10449 cells, grown in 0.5% glucose-containing complex medium, were packed into the well. The pH at the tooth/S. mutans interface was monitored continuously for 120 min after the addition of 0.5% glucose at 37°C. S. mutans cells were recovered from the wells, and the amounts of lactate and calcium were measured using a portable lactate meter and a fluorescent dye, respectively. Proteolytic activity was also evaluated fluorometrically. The pH of the RD/S. mutans interface was significantly higher than that of the CE/S. mutans interface (30 min: 6.37 ± 0.12 vs. 6.18 ± 0.11, 60 min: 6.08 ± 0.14 vs. 5.66 ± 0.27, 90 min: 5.49 ± 0.24 vs. 5.14 ± 0.22, p < 0.05). Greater amounts of calcium were dissolved from RD (3.19 ± 0.74 µg/mL) than from CE (1.84 ± 0.68 µg/mL; p < 0.05), while similar amounts of lactate were produced. Proteolytic activity was not detected at any of the interfaces. These results indicate that RD is more soluble to bacteria-induced acidification than CE. This method can contribute to the evaluation and development of caries-preventive materials.
评估牙表面/细菌界面的理化过程对于阐明龋齿的病因至关重要。本研究旨在比较冠釉质（CE）和根牙本质（RD）的矿物质溶解度和蛋白质降解，并使用牙齿/细菌界面模型研究溶解成分在细菌诱导的 pH 变化中的作用。一个形成井的聚甲基丙烯酸甲酯实验装置，将牛牙（CE 或 RD）标本固定在井的底部。将微型 pH 电极放置在牙齿上，将在含有 0.5%葡萄糖的复杂培养基中生长的变形链球菌 NCTC 10449 细胞装入井中。在 37°C 下加入 0.5%葡萄糖 120 分钟后，连续监测牙齿/变形链球菌界面的 pH 值。从井中回收变形链球菌细胞，并使用便携式乳酸计和荧光染料分别测量乳酸和钙的量。还通过荧光法评估蛋白水解活性。RD/S. mutans 界面的 pH 值明显高于 CE/S. mutans 界面（30 min：6.37 ± 0.12 vs. 6.18 ± 0.11，60 min：6.08 ± 0.14 vs. 5.66 ± 0.27，90 min：5.49 ± 0.24 vs. 5.14 ± 0.22，p < 0.05）。RD 从钙中溶解的量（3.19 ± 0.74 µg/mL）明显多于 CE（1.84 ± 0.68 µg/mL；p < 0.05），而产生的乳酸量相似。在任何界面都未检测到蛋白水解活性。这些结果表明，RD 比 CE 更容易受到细菌酸化的影响。该方法有助于评估和开发防龋材料。
