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Synthesis of a chitosan nanoparticle suspension and its protective effects against enamel demineralization after an in vitro cariogenic challenge Objective: Our study aims to synthesize, characterize, and determine the effects of a ChNPs suspension on human enamel after cariogenic challenge via pH-cycling. Methodology: ChNPs were synthesized by ion gelation and characterized by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering. Forty enamel blocks were divided into four groups (n=10/group): (i) ChNPs suspension; (ii) chitosan solution; (iii) 0.05% sodium fluoride (NaF) solution; and (iv) distilled water. Specimens were exposed to cariogenic challenge by cycling in demineralization solution (3 h) and then remineralized (21h) for 7 days. Before each demineralization cycle, the corresponding solutions were passively applied for 90 s. After 7 days, specimens were examined for surface roughness (Ra) and Knoop hardness (KHN) before and after the cariogenic challenge; % KHN change (variation between initial and final hardness), and surface topography by an optical profilometer. The data were analyzed by repeated-measures ANOVA, One-way ANOVA, and Tukey tests (α=0.05). Results: TEM images showed small spherical particles with diameter and zeta potential values of 79.3 nm and +47.9 mV, respectively. After the challenge, all groups showed an increase in Ra and a decrease in KHN values. Optical profilometry indicated that ChNPs-and NaF-treated specimens showed uneven roughness interspersed with smooth areas and the lowest %KHN values. Conclusion: The ChNPs suspension was successfully synthesized and minimized human enamel demineralization after a cariogenic challenge, showing an interesting potential for use as an oral formulation for caries prevention.

Objective: To assess the incidence of caries in a two-year period among low birth weight (LBW), very low birth weight (VLBW), and extremely low birth weight (ELBW) children considering socioeconomic indicators, dietary factors and oral hygiene. Material and Methods: A convenience sample was formed of 42 low birth weight children aged two to five years at baseline. Two examiners diagnosed caries using the World Health Organization criteria. Birth weight, socioeconomic indicators and diet were collected from medical records and questionnaires. Binomial models were used to estimate unadjusted and adjusted rate ratios (RR) and respective 95% confidence intervals for the factors evaluated. Results: Thirty-six children were re-examined after two years. The incidence of dental caries was 36.7%. The dmft index was 0.44 (±1.25) at baseline and increased to 1.36 (±3.85) at follow-up. VLBW children (1,000 to 1,500 g) (RR=0.23; 95%CI: 0.08-0.72) and LBW children (1,500 to 2,500 g) (RR=0.06; 0.01-0.55) had fewer carious lesions compared to ELBW children (<1,000 g). Carious lesions were more frequent among children with a lower income (RR=6.05; 1.05-34.84) and less frequent among those who did not consume sweetened juice, tea or yogurt (RR: 0.21; 0.07-0.62). Conclusion: An inverse dose-response relation was found between birth weight and the incidence of caries. A lower income and the consumption of sweetened beverages were risk factors for the development of caries.