Investigation of an alternative to enhance the protection of the salivary pellicle against dental erosion by the association of film-forming polymers and sodium fluoride

Author(s)

Letícia Oba Sakae

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia (FO/SDO)
• Defense date: 2024-05-06

Examining board members

Taís Scaramucci Forlin; Marilia Afonso Rabelo Buzalaf; Samira Helena Niemeyer; Daniela Prócida Raggio

• Advisor: Taís Scaramucci Forlin

Abstract

CHAPTER II. The present study evaluated the effect of solutions containing filmforming polymers at different concentrations and pH values, associated or not with sodium fluoride (F; 225 ppm F-), when applied during the initial phase of salivary pellicle formation to prevent hydroxyapatite (HA) dissolution. Carbopol, Chitosan, Linear Sodium Polyphosphate (LPP), Gantrez, and Propylene Glycol Alginate (PGA) were tested in three concentrations (low, medium, high), two pH values (native or adjusted), and associated or not with F. Distilled water, F, and a solution containing fluoride and tin (Sn/F; 225 ppm F- and 800 ppm Sn2+) served as controls, totalizing 63 groups. Hydroxyapatite crystals were pre-treated with human saliva for salivary pellicle formation (1 min), followed by treatment with experimental solutions (1 min), and exposed to saliva again (28 min). Subsequently, they were added to a 0.3% citric acid solution (pH=3.8), connected to an automatic titrator that added aliquots of 28 l 0.1 N HCl for a total reaction time of 5 minutes. Data were analyzed with one-way ANOVA and Tukey tests (=0.05). For Carbopol alone, concentrations of 0.1% (native pH), 0.06%, and 0.08% (both at adjusted pH) showed significantly lower HA dissolution than the negative control. Concentrations of 0.1% and 0.08% Carbopol, at both pH values, improved the effect of F against HA dissolution to a nearly identical level as Sn/F. All Chitosan and LPP-containing solutions significantly reduced HA dissolution compared to the control. For Chitosan, the concentration of 0.5% (at both pH values) enhanced the effect of F. LPP at 0.5% (natural pH) and all LPP associations with F surpassed the effect of F. Some Gantrez solutions significantly reduced HA dissolution, but Gantrez failed to enhance F protection. PGA was unable to reduce HA dissolution or enhance the effect of F. In conclusion, Chitosan, LPP, and some Carbopol and Gantrez solutions used alone could reduce HA dissolution. Only Carbopol, Chitosan, and LPP were able to enhance F protection, but for Carbopol and Chitosan, this was influenced by the polymer concentration. CHAPTER III. This in vitro study aimed to investigate the effect of film-forming polymers on the salivary pellicle modification for the protection against enamel erosion, in the presence or absence of sodium fluoride (F). One hundred and thirty-five specimens of bovine enamel underwent an erosive cycling, consisting of 5 initial cycles and an additional 10 cycles, representing initial and severe erosion, respectively. For the first 5 cycles, there was an initial exposure to human saliva for salivary pellicle formation (1 min), followed by pellicle modification with one of the 9 experimental solutions (1 min, n=15): water (negative control); Sn/F (225 ppm F-; 800 ppm Sn2+); F (225 ppm F-); and polymers (0.1% Carbopol; 0.5% Chitosan or 0.5% Linear Sodium Polyphosphate LPP) with or without F. The specimens were exposed to saliva once again, but for 28 min, followed by 1 min of immersion in 1% citric acid (pH 3.6, under agitation), totalizing 5 min of erosion after the completion of 5 cycles. For the additional 5 cycles, the erosive challenges were performed for 5 min, totalizing 30 min of erosion after 10 cycles. Relative surface hardness (rSH), relative surface reflection intensity (rSRI), surface loss (SL), and amount of calcium release (CaR) were determined after 5 and 10 cycles. Data were statistically analyzed (=0.05). After 5 cycles, Sn/F and Chitosan+F showed the best protection against erosion, with the highest rSH values and the lowest CaR values. The Carbopol polymer, whether associated with F or not, exhibited the lowest rSH and rSRI and the highest CaR. After 10 cycles, Sn/F and Chitosan+F continued to present the highest rSH and the lowest CaR, as did F. In conclusion, the solution containing Chitosan and F was the only one capable of enhancing the protective effect of the salivary pellicle against erosion; however, its effect was not superior to that of the Sn/F solution. CHAPTER IV. This in situ study assessed the effect of a solution containing chitosan associated with sodium fluoride on the salivary pellicle modification against enamel erosion. Twelve volunteers participated in this double-blind, crossover, 4-phase in situ study. The groups were: 1. Negative control (C distilled water); 2. Positive control (Sn/F 225 ppm F- + 800 ppm Sn2+); 3. Sodium fluoride (F - 225 ppm F-); 4. Chitosan + F (0.5% Chitosan + 225 ppm F-). The volunteers wore a mandibular device containing bovine enamel specimens (n=4/phase). Each phase consisted of 10 cycles: initial formation of the salivary pellicle (1 min), rinsing with the solutions (1 min), salivary pellicle formation (28 min), extra-oral erosive challenge (1% citric acid, natural pH) for 1 min in the first 5 cycles and for 2 min from the 6th cycle onward, totalizing 15 min of erosion. After 5 cycles, 2 specimens were evaluated for relative surface hardness (rSH). After 10 cycles, the surface loss (SL) of the remaining specimens (in m) was assessed by optical profilometry. Data were analyzed with repeated measures ANOVA and Tukey tests (=0.05). Chitosan + F showed significantly higher rSH and lower SL in comparison to the negative control (p=0.002 and p<0.001, respectively), but did not show a significant difference from F alone (p=0.894 and p=0.682, respectively). Sn/F showed significantly the highest rSH and the lowest SL compared to the other groups (p<0.001). The association of chitosan with F was able to modify the salivary pellicle, however, it was not able to improve the protective effect of F alone. (AU)

• FAPESP's process: 20/05374-0 - Investigation of an alternative to enhance the protection of the acquired salivary pellicle against dental erosion by the association of film-forming polymers and sodium fluoride
• Grantee: Letícia Oba Sakae
• Support Opportunities: Scholarships in Brazil - Doctorate