Billington R W, Hadley P C, Towler M R, Pearson G J, Williams J A
Eastman Dental Institute, London, UK.
Biomaterials. 2000 Feb;21(4):377-83. doi: 10.1016/s0142-9612(99)00199-4.
This investigates the effects of the addition of Na and F ions to a glass ionomer cement in which those ions are not inherently present on its interactions with dilute (0.2%) NaF solution. Both the effect of the solution on the cement's surface morphology and the effect of the cement on the solution in terms of take up of Na+ and F- and of change in pH are to be investigated. These results are to be compared to previous results obtained with glasses which contained both, one, or neither of the ions as components of their glasses. NaF (1.3% by weight in the mixed cement) was added to the powder components of a glass ionomer based on LG30 glass (which contains Al, Si, Ca, P, and O only). Discs of cement were set in moulds at 37 degrees C for 1 h then stored in water at 37 degrees C for 3 days. Each test disc was then immersed in 10 ml 0.2% NaF solution whereas controls remained immersed in water (N = 3 for test and control). Test and control disc surfaces were assessed both qualitatively by electron microscopy and quantitatively by linear profilometry (Ra values). Potentiometry was used to measure solution pH and Na and F concentrations using a pH electrode and suitable ion selective electrodes both before and after cement immersion. The surface of test specimens was subject considerable disruption with the polysalt cement matrix being removed and residual glass particles being disclosed. The controls showed no such disruption. This effect was reflected in a significant difference of Ra. Such an effect was not shown by test and control surfaces of LG30 but a similar effect was to that shown by LG26 (which contains F as a glass component). Solution pH changed by 1 unit which was much more than the change shown by LG30 or LG26 but is similar to that of AH2 and MP4 cements which both contain Na. The Na and F uptake was much lower than for LG30 whereas that of LG26 was higher than LG30. The Na:F ratio was 0.29:1 compared to 1.26:1 for LG30 (LG26 = 1.01:1, AH2 = 1.02:1, MP4 = 1.04:1). Fluoride addition to a F-free glass ionomer renders it vulnerable to surface disruption by NaF solution showing that fluoride complexes produced in glass dissolution are not necessarily involved in this process. Sodium addition to a Na-free glass ionomer confirms the role of this cement in enhancing pH change in NaF solution. The level of uptake of F- from a NaF solution in much lower than that for the F-free glass ionomer which shows there is no direct relationship between F- uptake and surface disruption. The ratio of Na:F uptake is below 0.3:1, but the pH change is similar to cements where the ratio is close to unity which indicates that F-/OH- interchange is not a significant mechanism even when anion/cation uptake is not balanced.
本研究考察了向玻璃离子水门汀中添加原本不存在的钠（Na）离子和氟（F）离子后，该水门汀与稀（0.2%）NaF溶液相互作用的情况。既要研究溶液对水门汀表面形态的影响，也要研究水门汀对溶液中Na⁺和F⁻的吸收以及pH变化的影响。这些结果将与之前用含有这两种离子中的一种、两种或都不含有这些离子作为玻璃成分的玻璃所获得的结果进行比较。将NaF（在混合水门汀中占1.3%重量）添加到基于LG30玻璃（仅含有铝、硅、钙、磷和氧）的玻璃离子水门汀的粉末成分中。将水门汀圆盘在37℃下置于模具中1小时，然后在37℃的水中储存3天。然后将每个测试圆盘浸入10毫升0.2%的NaF溶液中，而对照组则一直浸入水中（测试组和对照组N均为3）。通过电子显微镜对测试组和对照组圆盘表面进行定性评估，并通过线性轮廓仪（Ra值）进行定量评估。在水门汀浸入前后，使用pH电极和合适的离子选择性电极通过电位分析法测量溶液的pH值以及Na和F的浓度。测试样品的表面受到了相当大的破坏，聚盐水泥基质被去除，残留的玻璃颗粒暴露出来。对照组未出现这种破坏。这种影响反映在Ra值上有显著差异。LG30的测试组和对照组表面未显示出这种影响，但与LG26（其玻璃成分中含有F）显示的影响类似。溶液pH值变化了1个单位，这比LG30或LG26显示的变化要大得多，但与同样含有Na的AH2和MP4水门汀的变化相似。Na和F的吸收量比LG30低得多，而LG26的吸收量高于LG30。Na:F比率为0.29:1，而LG30为1.26:1（LG26 = 1.01:1，AH2 = 1.02:1，MP4 = 1.04:1）。向无氟玻璃离子水门汀中添加氟会使其易受NaF溶液的表面破坏，这表明玻璃溶解过程中产生的氟化物络合物不一定参与此过程。向无钠玻璃离子水门汀中添加钠证实了这种水门汀在增强NaF溶液pH变化方面的作用。从NaF溶液中吸收F⁻的水平远低于无氟玻璃离子水门汀，这表明F⁻吸收与表面破坏之间没有直接关系。Na:F吸收比率低于0.3:1，但pH变化与比率接近1的水门汀相似，这表明即使阴离子/阳离子吸收不平衡，F⁻/OH⁻交换也不是一个重要机制。
