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

建立了一种测定体内形成的牙菌斑中氟化物和矿物质分布的方法。在900 ppm氟化物冲洗前，冲洗后10分钟和24小时，以及在含有3%尿素和100 ppm氟化物的实验溶液中浸泡后，每天两次，连续4天，使用特殊装置反复收集同一受试者的菌斑样本。样品被冷冻干燥，然后包埋在甲基丙烯酸酯混合物中，用超显微切片机从表面到牙釉质切成3或6毫米厚的切片。较厚的切片收集在几层斑块样品中进行化学分析，较薄的切片用于测定斑块体积。将每个斑块样本放入氯仿中提取甲基丙烯酸酯。从沉积物中提取氟化物、钙和磷到酸性缓冲溶液（pH5.2）中。氟离子采用氟电极测定，钙和磷浓度分别采用分光光度和比色法测定。结果以每单位斑块体积表示。本方法允许检查氟化物、钙和磷在牙菌斑沿其整个厚度的分布。冲洗后10min，氟化物含量明显升高，说明氟化物已经迅速渗透到牙菌斑中。升高的氟化物浓度在24小时内几乎降至基线水平。研究发现，氟化物与接触氟化物溶液的牙菌斑中的矿物质之间存在高度显著的相关性。在尿素处理的斑块中，钙和磷之间的相关性明显高于没有尿素的氟化物暴露的样本。结果表明，该技术可用于评价牙菌斑/牙釉质界面中氟化物和矿物质的行为，以及氟化物应用的防龋效果。

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.