苹果酸对羟基磷灰石脱钙和化学吸附的研究

A Study on Decalcification and Chemosorption of Hydroxyapatite with Malic Acid

目的 研究苹果酸对牙体硬组织的酸蚀作用及其对羟基磷灰石 (HA)的化学吸附作用。方法 (1) 15 %苹果酸水溶液 10 78ml和 4 0 0 0mgHA混合 ,4 8h后分离固体生成物和滤液并反复冲洗固体 ,真空干燥 ,用傅里叶变换红外光谱法 (FTIR)进行定性和差错分析。 (2 )用 15 %苹果酸溶液酸蚀牙齿硬组织 15、30、6 0、12 0s后 ,干燥、喷金 ,扫描电镜观察表面形态。结果 苹果酸与HA反应后生成苹果酸钙盐有两种结构 ,一种溶解性较大 ,对HA有脱钙作用 ;另一种可溶性较小 ,可化学吸附于HA表面。延长酸蚀时间易生成沉积物阻塞牙本质小管。结论 苹果酸对HA具有脱钙 -吸附作用 。

Objective To detect the evidence of chemical bonding of the malic acid to calcium of hydroxyapatite and to observe the etching ability of the malic acid to tooth hard tissues.Methods After 15% (w/v) malic acid aqueous solution (10 78ml) was mixed with hydroxyapatite (HA)(400 0mg) for 48hrs, the precipitation and the filtration sloution were separated and dried in a vacum over silica gel. Fourier transform infrared spectrophotometer (FTIR) measurement and subtraction technique were performed for the dried precipitation and the desiccate filtration. Four pieces of tooth disks were etched respectively with the malic acid solution for 15s, 30s, 60s and 120s, then rinsed, dried and gold sputtered. Scanning electron microscopy(SEM) was used to examine the effects of the different malic acid etching times on the micro morphology of the enamel and dentin surface.Results FTIR revealed that there were typical bands of carboxylic salt after the reaction of HA and malic acid which generated two types of calcium malate. One had an etching ability on tooth due to two carbonyl groups reacting with calcium and the other had the chemosorption to HA owing to one carbonyl group reacting with calcium. Prolonged etching time made it easier to generate calcium malate crystals which might occlude deatin tubules.Conclusion The tooth hard tissues could be decalcified and chemically bonded by malic acid.