Fluoride rechargeable layered double hydroxide powders for dental applications

Abstract

It has been widely reported that the prevention of early-stage carious lesions requires a sustained therapeutic low-level release of fluoride in the oral cavity. However dental caries remains as one of the most prevalent diseases worldwide. Therefore, there is a requirement for the development of a material capable of releasing fluoride at a therapeutic level. Layered double hydroxides (LDH) have the potential to achieve this by taking up and releasing fluoride repeatedly, such as recharging using a fluoride toothpaste/mouthwash. A range of fluoride rechargeable LDH powders; ZnAl, MgAl (1:1, 2:1 and 3:1) and CaAl (1:1 and 2:1) were successfully synthesised at different ratios and characterised (pXRD, FTIR, SEM and F− ISEs). NiAl LDH did not form an LDH structure at all ratios. The fluoride uptake (from sodium fluoride, NaF) and release (de-ionised water, DW) over two cycles (24 h) from these powders, demonstrated an increase in the LDH lattice interlamellar space and an increase in fluoride uptake in the following order of formulations; CaAl>MgAl>ZnAl LDH. 2:1 MgAl demonstrated the greatest fluoride release with the same amount released during release and re-release. Therefore, LDH has the potential to be incorporated into various applications, while altering the composition or ratio to obtain a desired fluoride uptake or release.