Development of 2% w/w sodium fluoride oral gels for prevention of dental caries in patients with xerostomia

Abstract

For prevention of dental caries in xerostomic patients, 2% w/w sodium fluoride oral gel is frequently prescribed; however, the product has not been officially approved for clinical use in Thailand. Therefore, this study aimed to develop 2% w/w sodium fluoride oral gels dispensed specifically to patients in Rajavithi Hospital. Both single and combined gel bases were prepared from different gelling agents, including gelatin, xanthan gum, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, and Carbopol 940P. They were subsequently characterized according to their physicochemical properties, i.e., clarity, spreadability, pH values, and apparent viscosity. All the gel bases were clear viscous liquids of good spreadability, except the xanthan gum gel bases, which were slightly cloudy. The pH values indicate that the gelatin, xanthan gum, and Carbopol 940P gel bases were acidic, while the cellulose gel bases were neutral. The apparent viscosity ranged from 3 to 11.5 x 105 cPs, depending mainly on type and concentration of the gelling agents. After preparation, the gel bases were then incorporated with 1 M pH 7.4 phosphate buffer solution to the final concentration of 5% w/w. Macroscopic characteristics of the buffered gel bases were generally unchanged, except for the apparent viscosity, which decreased slightly. Sodium fluoride was subsequently added to the selected buffered gel bases. The resulting sodium fluoride gels were neutral and transparent viscous liquids of good spreadability and exhibited good stability against the heating-cooling cycle and accelerated testing. Thus, it is conceivable that 2% w/w sodium fluoride oral gels with acceptable physicochemical characteristics and excellent stability were successfully developed.