Effects of Different Toothpastes on the Nanomechanical Properties and Chemical Composition of Resin-Modified Glass Ionomer Cement and Composite Resin Restorations.

PURPOSE: This study evaluates the effects of different toothpastes on the nanohardness and chemical compositions of restorative materials and dental surfaces. METHODS: Bovine enamel (n = 72) and dentin (n = 72) blocks were obtained and restored using RMGIC (n = 36) or CR (n = 36) to create the following surfaces: dentin adjacent to RMGIC (DRMGIC), enamel adjacent to RMGIC (ERMGIC), dentin adjacent to CR (DCR), and enamel adjacent to CR (ECR). After restoration, one hemiface of each specimen was coated with an acid-resistant varnish to facilitate the creation of control (C) and eroded (E) sides; the latter were achieved by erosion-abrasion cycles as follows: erosion with 1% citric acid: 5 days, four times for 2 min each day; 1% citric acid/abrasion, two times for 15 s, followed by immersion in a toothpaste slurry for 2 min. Toothpastes without fluoride (WF; n = 12), with sodium fluoride (NaF; n = 12), and with stannous fluoride (SnF2; n = 12) were used for RMGIC or CR. The specimens were analyzed for nanohardness (H), and chemical composition using energy-dispersive X-ray spectroscopy and Raman microscopy. The data were statistically analyzed using two-way repeated measures ANOVA and Tukey's test (α = 0.05). RESULTS: Lower H values were obtained with NaF for DRMGIC-C, with a statistically significant difference from the H value obtained with WF (p < 0.05). The calcium and phosphorus concentrations in DCR-E were significantly lower with WF than with the other types of toothpaste (p < 0.05). Fluoride-containing toothpastes are capable of preserving the main chemical components of the dentin adjacent to the restorative materials under erosive-abrasive conditions.

Effects of consumption of contaminated feed with 2,4-dichlorophenoxyacetic acid (2,4-D) on the rat tibia: analysis by Raman spectroscopy and mechanical properties.

Studies reported the harmful effects of 2,4-D on body tissues, provoking changes in the anatomy and physiology of the kidneys, liver, and testicles. Thus, the objective was to evaluate if there were alterations in the bone quality of the tibia of rats submitted to feed consumption that were exposed to three different 2,4-D doses. Male Wistar rats were divided into four groups: oral control group (C: feed consumption without 2,4-D contamination); low oral concentration group (G3: contaminated feed with low concentration of 2,4-D); medium concentration group (G6: contaminated feed with medium concentration of 2,4-D); and high concentration group (G9: contaminated feed with high concentration of 2,4-D). The results demonstrated alterations of the mechanical properties and Raman ratios of the tibias of the contaminated groups. The maximum load, maximum stress, elastic modulus, and the cortical area were lower in the G6 and G9 compared to C group. The mineral-to-matrix ratio (relative mineral to organic content) was lower in the G6 and G9 groups compared to C group, but carbonate-to-matrix ratio (indicator of bone turnover) was higher in both groups. Thus, it is possible to suggest that the 2,4-D herbicide performed deleterious effects on the bone quality of male Wistar rats.