Experimental polymer-based toothpastes protection against enamel demineralization

To evaluate the demineralization-inhibiting properties of 0.5% chitosan (CHI) and 2% sodium linear polyphosphate (LPP) alone or associated with fluoride (1350 ppm, NaF) and/or stannous (3500 ppm, SnCl₂) plus fluoride ions in experimental toothpaste formulations.

Bovine enamel specimens were randomly allocated into 12 groups (n = 14) and subjected to a 5-day pH cycling period (3-h demineralization 2 × /d, 1-min 1:3 toothpaste slurry 2 × /d, remineralization all other times). Sections were analyzed using digital transverse microradiography (integrated mineral loss-ΔZ, lesion depth-L, and maximum mineral density of the lesion surface zone-SZ_max). The fluoride availability in the toothpaste slurry was measured using an ion-selective electrode. ANOVA was used to test for a group effect, followed by pair-wise comparisons using Fisher's Protected Least Significant Differences (alpha=0.05).

For the ΔZ data, CHI and LPP in isolation did not differ from placebo [geometric means (confidence intervals); vol%min x µm]: [4561(3852,5401)] and [4582 (3890,5396)] vs. [5168(4369,6114)], respectively, (p ≥ 0.268), and did not provide additional protection when associated with F [1843 (1531,2219)], Sn [5080(4354,5926)] and F+Sn [2298(1860,2838)]. Sn-containing toothpastes did not differ from placebo (p ≥ 0.05). All F-based toothpastes resulted in less demineralization than F-free toothpastes. The L data followed similar trends to the ΔZ data. The SZ_max data showed that CHI and LPP did not differ from placebo: vol%min 1 (35,49) and 42 (34,51) vs. 46 (41,51), respectively (p > 0.243). When associated with F, only CHI [29(21,40)] presented less mineral content at the surface lesion, and the polymers did not provide additional mineral content at the surface layer when associated with Sn [38(34,44), p > 0.377], or F+Sn [15(36,57), p > 0.23]. For the mean mineral distribution for all lesions as a function of experimental toothpastes, some lesions showed surface softening without a clear lesion body (F), and some lesions showed a more pronounced (Placebo). The fluoride values ranged from 0 (Placebo) to 1490 (CHI+F).

None of the polymers could enhance the protection provided by fluoride or fluoride plus stannous.