Viscosity of chitosan impacts the efficacy of F/Sn containing toothpastes against erosive/abrasive wear in enamel

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ObjectivesChitosan (Ch) in F/Sn-toothpastes can increase toothpastes’ anti-erosive efficacy. Whether efficacy can be further increased by changing chitosan’s viscosity was study aim. Methods192 human enamel specimens were assigned to 2 × 6 groups (n = 16 each): Four F/Sn (500 ppm F−, 800 ppm Sn2+) toothpastes with chitosan (0.5 %, viscosity 50, 500, 1000 or 2000 mPas), negative-control (no F/Sn/chitosan), positive-control (F/Sn, no chitosan). The study was conducted in two experiments (E1/E2). Specimens were cyclically demineralised (10 d, 6 × 2 min/d; 0.5 % citric acid); half of groups (E1) was exposed to toothpaste slurries (2 × 2 min/d), the other half was additionally brushed (2 × 15 s/d, E2). Tissue loss (mean ± SD, μm) was quantified profilometrically. Element analysis (EDX, wt%) on specimen surfaces and on toothpastes’ particulate fraction and SEM analysis of specimen surfaces were performed. ResultsTissue loss in negative-controls (E1/E2) was 4.96 ± 1.55/12.76 ± 2.45. Toothpastes with active agents (AA) reduced tissue loss compared to negative-control (p < 0.0001). E1: All AA caused precipitates, being the thickest after Ch500. Chitosan increased carbon retention, not tin retention. E2: Only Ch1000 increased efficacy (-0.97 ± 4.48) compared to positive-control (2.98 ± 1.32; p = 0.05). EDX showed comparable carbon values in all AA; tin content was higher in Ch1000 (6.5 ± 3.4) compared to other AA (range: 3.8 ± 0.3–4.3 ± 1.3). On abrasives, tin adsorption was decreased by all chitosans. SEM revealed minor structural differences. ConclusionsChitosan viscosity has impact on efficacy of F/Sn toothpastes. Under erosive/abrasive conditions Ch1000 showed the best protective effect with higher tin retention on surfaces and lower tin absorption by abrasives. Clinical significanceThe biopolymer chitosan shows protective effect against enamel erosion and erosion/abrasion when used in an F/Sn toothpaste with specific viscosity.