Abstract The layer formed by fluoride compounds on tooth surface is important to protect the underlying enamel from erosion. However, there is no investigation into the properties of protective layer formed by NaF and TiF4 varnishes on eroded enamel. This study aimed to evaluate the thickness, topography, nanohardness, and elastic modulus of the protective layer formed by NaF and TiF4 varnishes on enamel after erosion using nanoindentation and atomic force microscopy (AFM). Human enamel specimens were sorted into control, NaF, and TiF4 varnish groups (n = 10). The initial nanohardness and elastic modulus values were obtained and varnishes were applied to the enamel and submitted to erosive challenge (10 cycles: 5 s cola drink/5 s artificial saliva). Thereafter, nanohardness and elastic modulus were measured. Both topography and thickness were evaluated by AFM. The data were subjected to ANOVA, Tukey’s test and Student’s t test (α = 0.05). After erosion, TiF4 showed a thicker protective layer compared to the NaF group and nanohardness and elastic modulus values were significantly lower than those of the control group. It was not possible to measure nanohardness and elastic modulus in the NaF group due to the thin protective layer formed. AFM showed globular deposits, which completely covered the eroded surface in the TiF4 group. After erosive challenge, the protective layer formed by TiF4 varnish showed significant properties and it was thicker than the layer formed by NaF varnish.

The purpose of this study was to evaluate the inflammatory and cure events of acid-based reactions using glass ionomer cement used for cementation of crowns, bridges, onlays and orthodontic bands implanted in subcutaneous tissue, at different time intervals. A total of 48 male Wistar rats were used, distributed into 4 groups (n = 12), as follows: Group C (control, polyethylene), Group ME (Meron), Group KC (Ketac Cem) and Group PR (Precedent). The animals were sacrificed after time intervals of 7, 15 and 30 days, and their tissues were analyzed under an optical microscope for such events as inflammatory infiltrate, edema, necrosis, granulation tissue, multinucleated giant cells, young fibroblasts and collagen. The results was assessed using Kruskal-Wallis and Dunn's tests (p < 0.05). In the initial period, intense inflammatory infiltrate was observed for all the materials with no significant difference among them (p = 0.104). Groups PR and KC showed significant difference in relation to Group C, at 7 days (p = 0.025) and 15 days (p = 0.006). Edema and giant cells were more expressive in Group ME, differing significantly from Groups C (p = 0.023) and KC (p = 0.039), respectively, at 7 days. Group ME showed a statistically significant difference in relation to Groups PR and KC for the presence of young fibroblasts (p = 0.009) and for collagen (p = 0.002), at 7 days. Within the limits of this in vivo study, Precedent and Ketac Cem glass ionomer cements showed better tissue healing with a greater number of fibroblasts and collagen, as compared to Meron.

The aim of this study was to assess the effect of different remineralizing agents on enamel microhardness (KHN) and surface topography after an erosive challenge. Forty-eight human enamel specimens (4 × 4 mm) were randomly assigned to 4 groups: control (no treatment), fluoride varnish, calcium nanophosphate paste and casein phosphopeptide-amorphous calcium phosphate paste (CPP-ACP). Both pastes were applied for 5 minutes, and fluoride varnish, for 24 h. Four daily erosive cycles of 5 minutes of immersion in a cola drink and 2 h in artificial saliva were conducted for 5 days. KHN readings were performed at baseline and after 5 days. The percentage of enamel hardness change (%KHN) was obtained after erosion. The surface topography was evaluated by atomic force microscopy (AFM). The data were tested using ANOVA, Tukey's and paired-T tests (p < 0.05). After an erosive challenge, there was no statistically significant difference between the control (96.8 ± 11.4 KHN / 72.4 ± 3.0 %KHN) and the varnish (91.7 ± 14.1 KHN / 73.4 ± 5.5 %KHN) groups. The nanophosphate group showed lower enamel hardness loss (187.2 ± 27.9 / 49.0 ± 7.9 %KHN), compared with the CPP-ACP group (141.8 ± 16.5 / 60.6 ± 4.0 %KHN), and both were statistically different from the varnish and the control groups. AFM images showed a rough surface for the control and the varnish groups, a non-homogeneous layer with globular irregularities for CPP-ACP, and a thick homogeneous layer for the nanophosphate group. None of the agents provided protection against the development of erosion; however, nanophosphate paste was able to reduce enamel surface softening after the erosive challenge