The use of nanoparticles (NPs) has become a significant area of research in Dentistry. Objective The aim of this study was to investigate the physical, antibacterial activity and bond strength properties of conventional base, core build and restorative of glass ionomer cement (GIC) compared to GIC supplemented with titanium dioxide (TiO2) nanopowder at 3% and 5% (w/w).Material and Methods Vickers microhardness was estimated with diamond indenter. Compressive and flexural strengths were analyzed in a universal testing machine. Specimens were bonded to enamel and dentine, and tested for shear bond strength in a universal testing machine. Specimens were incubated with S. mutans suspension for evaluating antibacterial activity. Surface analysis of restorative conventional and modified GIC was performed with SEM and EDS. The analyses were carried out with Kolmogorov-Smirnov, ANOVA (post-hoc), Tukey test, Kruskal-Wallis, and Mann Whitney.Results Conventional GIC and GIC modified with TiO2 nanopowder for the base/liner cement and core build showed no differences for mechanical, antibacterial, and shear bond properties (p>0.05). In contrast, the supplementation of TiO2 NPs to restorative GIC significantly improved Vickers microhardness (p<0.05), flexural and compressive strength (p<0.05), and antibacterial activity (p<0.001), without interfering with adhesion to enamel and dentin.Conclusion GIC supplemented with TiO2 NPs (FX-II) is a promising material for restoration because of its potential antibacterial activity and durable restoration to withstand the mastication force.

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Objective: The purpose of this study was to evaluate, using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the morphological and structural changes of the enamel after irradiation with the Er:YAG laser. Background data: A previous study showed that subablative Er:YAG laser irradiation produced undesirable morphological changes on the enamel surface, such as craters and cracks; however, the enamel acid resistance was not increased. Methods: Fifty-two samples of human enamel were divided into four groups (n ¼ 13): Group I was the control (no laser irradiation), whereas Groups II, III, and IV were irradiated with the Er:YAG 100 mJ (12.7 J /cm 2 ), 100 mJ (7.5 J/cm 2 ), and 150 mJ (11 J/cm 2 ), respectively, at 10 Hz with water spray. The morphological changes were observed by AFM and SEM. The weight percentages (wt%) of calcium (Ca), phosphorus (P), oxygen (O) and chlorine (Cl) were determined in the resultant craters and their periphery using EDS. Kruskal-Wallis and Mann-Whitney U tests were performed ( p 0.05) to distinguish significant differences among the groups. Results: The AFM images showed cracks with depths between 250 nm and 750 nm for Groups II and IV, respectively, and the widths of these cracks were 5.37 mm and 2.58 mm. The interior of the cracks showed a rough surface. The SEM micrographs revealed morphological changes. Significant differences were detected in Ca, P, and Cl in the crater and its periphery. Conclusions: AFM observations showed triangular-shaped cracks, whereas craters and cracks were evident by SEM in all irradiated samples. It was not possible to establish a characteristic chemical pattern in the craters.

Morphological changes of Er:YAG irradiated enamel represented mild to severe damages. Conditions employed in this study are not recommended for deciduous caries prevention. Er:YAG energy density influenced chemical changes in enamel to enhance its structure. Acid dissolution removed fluoride from enamel surface.