Effect of experimental polymer-containing solutions in preventing caries-like lesions on enamel

OBJECTIVES: To evaluate experimental solutions containing polymers (Chitosan: CHI, Sodium linear polyphosphate: LPP, Polyacrylic acid: PAA; and 2-methacryloyloxyethyl phosphorylcholine: MPC) isolated, associated or not with fluoride (F), stannous ions (Sn), or F+Sn in vitro against caries-like lesion in enamel. DESIGN: Bovine enamel sections were randomly allocated into 20 groups (n = 14): Distilled water (DIW, negative control), F: 220 ppm F<sup>-</sup>, Sn: 800 ppm Sn<sup>2+</sup>, F+Sn, and four polymers (0.5 % CHI, 2 % LPP, 0.1 % PAA, 2 % MPC) associated or not to F, Sn, or F+Sn. The single sections were individually subjected to a pH cycling: demineralization (3 h, 2 ×/d), experimental solution (1 min, 2 ×/d), and remineralization (overnight), for 5d. The enamel sections were analyzed using digital transverse microradiography (integrated mineral loss-ΔZ, and lesion depth-L). Data were analyzed using Kruskal-Wallis and Wilcoxon rank sum tests, with alpha= 0.05. RESULTS: When tested in isolation, LPP was the only polymer affording greater protection than DIW, while PAA enhanced ΔZ [median (Q1-Q3); vol%min× µm: 2530 (2070-3140) vs. 3710 (3410-3860) vs. 4375 (3820-4990) respectively; all p < 0.05]. None of the polymers could increase the protection provided by F [1430 (1340,1570), p = 0.084] or F+Sn [1515(1150-1940), p = 0.182)]. CHI [2525(1890-3210), p = 0.01] and LPP [3105 (2460-3250), p = 0.006] increase the protection offered by Sn [3500 (3350-3790)], but PAA enhanced ΔZ [4340 (3540-4820), p = 0.044]. For L data, there are no polymer effects compared to DIW [93.30(82.60-104.80), p = 0.177], F [78.25(70.40-90.30), p = 0.340] or F+Sn [73.05(54.60-81.00), p = 0.056]. Only MPC decrease the degree effect of Sn [113.10 (110.40-124.30) and 99.20(92.60, 105.80), p = 0.003]. CONCLUSIONS: LPP was the only polymer that protected enamel against demineralization when tested in isolation. However, none of the polymers could increase the protection offered by fluoride or fluoride plus stannous ions.