A METHOD FOR DETERMINING THE DISTRIBUTION OF FLUORIDE IN HUMAN DENTAL PLAQUE in vivo AND THE EFFECT OF SOME FACTORS ON THE FLUORIDE DISTRIBUTION

建立了一种测定活体牙菌斑中氟和矿物质分布的方法。使用特殊设备重复采集同一受试者的菌斑样本，在一次900ppm氟化物漂洗之前，漂洗后10min和24小时，以及在含有3%尿素和100ppm氟化物的实验溶液中浸泡后，每天两次，共4天。这些样品被冷冻干燥，然后嵌入到甲基丙烯酸酯混合物中，并使用超显微切割器从表面向牙釉质切成3微米或6微米厚的切片。收集多个分层斑块标本中较厚的切片进行化学分析，较薄的切片用于测定斑块体积。每个菌斑样本都放在氯仿中提取甲基丙烯酸酯。将底泥中的氟、钙和磷提取到酸性缓冲溶液(pH5.2)中。用氟化物电极测定氟，用分光光度法和比色法分别测定钙和磷的浓度。结果以每单位斑块体积表示。本方法可以检测氟、钙和磷在斑块中沿整个斑块厚度的分布。漂洗10min后，整个样本的氟含量显著增加，表明氟化物已迅速渗透到菌斑中。氟化物浓度在24 h内几乎降至基线水平。氟化物与斑块中矿物质之间存在高度显著的相关性。尿素处理的菌斑中钙磷的相关性显著高于不含尿素的氟暴露的样品。结论：该技术可用于评价氟化物和矿物质在牙菌斑/牙釉质界面上的行为，以及氟化物的防腐效果。

A method for the determination of the fluoride and mineral profiles within dental plaque formed in vivo has been developed. Plaque samples were repeatedly collected using special devices from the same subject, before a single 900 ppm fluoride rinse and, 10min and 24h after the rinse, and also after immersed in an experimental solution containing 3% of urea and 100 ppm fluoride twice a day on 4 days. The samples were freeze-dried and then embedded in a methacrylate mixture and were sliced from the surface towards the enamel into 3 mum or 6 mum thick sections using an ultra microtome. The thicker sections were collected in several layred plaque samples for the chemical analysis, and the thinner sections were used for determination of plaque volume. Each plaque sample was placed in chloroform to extract the methacrylate. Fluoride, calcium and phosphorus were extracted from the sediment into an acid buffer solution (pH5.2). Fluoride was determined using a fluoride electrode, and concentrations of calcium and phosphorus were determined by sectroscopical and colorimetrical techniques respectively. Results were expressed per unit of plaque volume. The present method allowed examination of fluoride, calcium and phosphorus distribution in plaque along its entire thickness of plaque. Fluoride content significantly increased throughout the sample 10min after rinsing, indicating that fluoride had rapidly penetrated into the plaque. The elevated fluoride concentrations diminished almost to baseline levels within 24 h. A high significant correlation was found between fluoride and minerals in the plaque exposed to the fluoride solutions. Correlation between calcium and phosphorus was significantly higher in the urea treated plaque than the sample exposed fluoride without urea. It is conclued that this technique will be useful for evaluating the fluoride and mineral behavior in the plaque/enamel interface, and the anti-caries efficacy of the fluoride application.