Evaluation of the protective potential of film-forming polymers combined to fluoride solutions against erosive tooth wear

Abstract

Several preventive approaches have been proposed as attempts to control tooth erosion, including fluoride products, polyvalent metallic cations, as well as bioadhesive polymers, in order to form surface protective films and increase the substantivity of the actives present in the fluoride products. Different polymers have been tested in view of their antierosive potential. Our research group has obtained promising results with polymethacrylate polymers, which resulted on a patent registered in INPI. Nevertheless, additional tests are still needed to check the benefits of solutions when abrasion challenges are associated to erosion, on enamel and dentin (stage 1), alternative of vehicles to increase of the active agents in formulations for professional use (stage 2), as well as to verify the benefits in conditions more closely related to clinical situations, considering its effects on the protective potential of acquired pellicle (stage 3). Thus, the objective of this proposal is to evaluate the protective potential of copolymers of polymethacrylate (aminomethacrylate-AMC and methylmethacrylate-MMC) combined with fluoride solutions, on the control of the erosive tooth wear progression, as well as its influence on the protective effect of the acquired pellicle against erosive and abrasive challenges. The proposal is divided in 3 stages. In the first stage, the protective effect of the AMC associated to fluorides against enamel and dentin erosion and erosive wear of after erosive and abrasive challenges will be tested. 90 enamel and bovine specimens will be allocated to six treatment groups with the following solutions simulating mouthwashes (n=15): water (control); AMC 2%; sodium fluoride (F- NaF - 225 ppm F-); F + AMC; NaF + Stannous Chloride (SF- SnCl‚- 800 ppm Sn+2); FS + AMC. The specimens will be subjected to erosion and abrasion cycles for 5 days with 0.3% citric acid (ph 2.6) for 5 min, 4x/day, and intervals of 1h in saliva. The protective potential will be evaluated by microhardness and surface loss will be assessed by profilometry (in µm). In the stage 2 study, the protective effect against erosive enamel wear promoted by vehicles similar to varnishes, allowing surface pellicles formed by more concentrated formulations prepared with the copolymers AMC and MMC associated to NaF, will be evaluated. 90 enamel specimens will be allocated to six treatment groups: water (negative control); Duraphat varnish (NaF 5% - 22600 ppm F-) (positive control); AMC (15%); MMC (15%); AMC associated to NaF 5% (22600 ppm F-); MMC associated to NaF 5%. The same erosive and abrasive cycles described for study 1 will be used, and surface loss will be assessed by profilometry (in µm). In stage 3, the effect of the association of solutions containing F (Sodium Fluoride NaF - 225 ppm F-) and/ or S (Stannous Chloride SnCl‚ - 800 ppm Sn+2) and/ or AMC copolymer (2%) on the antierosive potential of the acquired pellicle over enamel and dentin, will be analyzed, considering erosive challenges, using a randomized cross-over in situ model. Twelve volunteers will install an intraoral device containing (two enamel and two dentin bovine) for 5 min. Afterwards, they will rinse with one of the solutions (5 ml - 1 min) and wait for 30 min, to allow the maturation of the acquired pellicle. Then, the specimens will be subjected to the erosive challenge with 0.03% HCl, pH 2.3 for 3 min extraorally. These steps will be repeated with five applications of solutions: water (negative control); F; S; AMC; FS; F associated with AMC; FS associated with AMC, one in each different phase. After the end of the cycle, the enamel and dentin surface microbiopsy will be performed with 0.03% HCl, pH 2.3 for 3 min. The assessment of the calcium and phosphorous concentration of the acidic samples will be performed with colorimetric spectrophotometry. The data will be analyzed according to the appropriate statistics, considering a 5% significance level. (AU)