Synthesis and characterization of calcium-containing sodium cyclotriphosphate and its protective effect on enamel erosion in vitro.

Objective: The objective of the present study was to synthesize and characterize sodium cyclotriphosphate (NaTMP) containing calcium and verify its effect using an initial enamel erosion model.

Methods: Cyclotriphosphate containing calcium (CaNaTMP) was synthesized using column chromatography, and addition of a solution with calcio hydroxide supernatant and analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. To determine the effect on enamel initial erosion, sound bovine enamel blocks (n = 96) were selected by initial surface hardness and divided into to 8 experimental groups (12 blocks/group): control (deionized water), 0.24 % NaF (1100 F), 0.25 %, 0.5 % and 1 % NaTMP and CaNaTMP at the same concentrations. The enamel blocks were immersed in 4 mL of experimental solutions for 2 min followed by 4 erosive challenges (citric acid, 0.75 %, pH 3.5, for 1 min, under stirring). The surface hardness was determined after each acid challenge. Data were subjected to two-way repeated measures analysis of variance, followed by Tukey's test (p < 0.05).

Results: The synthesis process led to the replacement of atoms of Na by atoms of Ca with particle sizes like those of NaTMP. Solutions containing CaNaTMP promoted superior reducing in hardness loss when compared to their counterparts without calcium (p < 0.001) and 1100 F (p < 0.001), during erosive challenges. A dose-response was observed for the CaNaTMP groups, with higher values for 1 % CaNaTMP and lower values for 0.25 % CaNaTMP (p < 0.001).

Significance: Solutions containing CaNaTMP led to superior protective effects compared to the 1100 F group on initial enamel erosion.