Rølla G
Dental Faculty, University of Oslo, Norway.
Acta Odontol Scand. 1988 Dec;46(6):341-5. doi: 10.3109/00016358809004786.
The literature concerning the formation and stability of CaF2 in the oral environment is reviewed. In early work the CaF2 formed during topical application with fluoride was assumed to be beneficial. It was suggested that it could protect the enamel surface directly or provide free fluoride ions for subsequent incorporation into the hydroxyapatite lattice. However, McCann claimed, in 1968, that CaF2 is soluble in saliva (12-15 mg/l), that it would be rapidly lost in the oral cavity, and that the clinical effect of fluoride was related to formation of firmly bound fluoride only. In this period many authors reported total loss of CaF2 during 24 h after a topical application of fluoride. It has now been shown in several laboratories that calcium fluoride is stable in saliva at neutral pH owing to surface adsorption of HPO2-4 to the crystal surface and formation of a solubility-limiting phase. Extended exposure of saliva can cause formation of a fluorapatite layer on the CaF2 crystals, restricting their dissolution further. Low pH (pH less than 5) causes loss of the solubility-limiting adsorbed HPO2-4 and a slow dissolution of CaF2. The CaF2 crystals may thus serve as pH-controlled reservoirs of fluoride ions on the enamel or in plaque and release fluoride during caries challenges. It is suggested that calcium fluoride is an essential phase explaining important aspects of the mechanism of topically applied fluoride, contrary to what was assumed in the past.
本文综述了有关口腔环境中氟化钙形成和稳定性的文献。在早期的研究中，人们认为局部应用氟化物时形成的氟化钙是有益的。有人提出，它可以直接保护牙釉质表面，或提供游离氟离子，以便随后结合到羟基磷灰石晶格中。然而，麦肯在1968年声称，氟化钙可溶于唾液（12 - 15毫克/升），它会在口腔中迅速流失，而且氟化物的临床效果仅与牢固结合的氟化物的形成有关。在这一时期，许多作者报告称，局部应用氟化物后24小时内氟化钙会完全流失。现在，几个实验室已经表明，由于HPO₂⁻₄在晶体表面的吸附以及形成了溶解度限制相，氟化钙在中性pH值的唾液中是稳定的。唾液的长时间接触会导致氟化钙晶体表面形成氟磷灰石层，进一步限制其溶解。低pH值（pH小于5）会导致溶解度限制吸附的HPO₂⁻₄流失，氟化钙缓慢溶解。因此，氟化钙晶体可以作为牙釉质或牙菌斑上氟离子的pH值控制储存库，并在龋齿发生时释放氟离子。有人提出，与过去的假设相反，氟化钙是解释局部应用氟化物机制重要方面的一个关键相。
