ABSTRACT
Background: Silver nanoparticles (AgNPs) are an effective antibacterial agent, and their inclusion in orthodontic adhesives has been proposed to prevent white spot lesions (WSLs). The objective of this study was to evaluate by Raman microscopy the preventive effect of an orthodontic adhesive modified with AgNPs on the formation of WSLs. Material and Methods: AgNPs were added in four concentrations (0.05%, 0.1%, 0.5%, and 1%) to an orthodontic adhesive. Metal brackets were bonded with the experimental adhesives, and the specimens were subjected to a microbial model for caries induction. The preventive effect on the formation of WSLs was evaluated by Raman microscopy, considering the intensity peak of the phosphate ion at 960 cm-1. The acquisition mode was linear scanning in the most representative lesion area, with a length of 136µm. Intensity values expressed the relative amount of phosphate ions remaining in the lesion. Microphotographs were analyzed in the Image J program to assess the depth of the lesions. Results: Significant differences were observed between all groups (P <0.05). The addition of 1% AgNPs effectively maintained the relative amount of phosphate ions close to sound enamel values. Furthermore, as the concentration of AgNPs increased, the depth of the lesions decreased. Conclusions: AgNPs were effective in decreasing the formation of WSLs. At a higher concentration of AgNPs, a more significant preventive effect on the formation of WSLs results in a relative amount of phosphate ion close to sound enamel values. Key words:White spot lesions, antibacterial, orthodontics, Raman microscopy, adhesive, Silver-nanoparticles.
ABSTRACT
BACKGROUND: There are different etching gels available, which have different composition, different pH, and different viscosity, and there is little information in the literature comparing all these products. OBJECTIVE: To evaluate the mean microshear bond strength and morphological characteristics of tooth enamel by evaluating different phosphoric acids combined with a universal adhesive system. MATERIALS AND METHODS: Eighty-four enamel samples were used, which were divided according to the acid conditioning: G1: Scotchbond Etchant (3M Oral Care), G2: Ultra-Etch (Ultradent), G3: Eco-Etch (IvoclarVivadent), G4: ETCH-37 with BAC (Bisco), G5: Etching gel (Densell), G6: Condac 37 (FGM), and G7: Scotchbond Universal Adhesive (3M Oral Care) in self-etch mode. For the adhesive procedure, Scotchbond Universal Adhesive was the one used as indicated the manufacturer's instructions, 0.9-mm-diameter resin cylinders were placed. The microshear bond strength test was performed after being stored for 24 hours in water. The morphological characteristics of tooth enamel were analyzed using the Raman confocal microscope alpha300RA. The analysis of variance (ANOVA) test and Tukey post-test were used to analyze the differences between the groups. RESULTS: The mean microshear bond strength values obtained for groups 1, 4, 5 were significantly greater than groups 2, 3, 6 and 7 (p < .05). All groups presented demineralization after the application of the etching acid, and few signs of demineralization were evident in group 7. CONCLUSIONS: Acid-etching with ETCH-37 with BAC, Etching gel, and Scotchbond Etchant improved the adhesive strength in the enamel using an universal adhesive, and acid-etching with Condac 37, Ultra-Etch, and Eco-Etch provides similar adhesive strength values to self-etch mode of universal adhesive. CLINICAL SIGNIFICANCE: All acid etchants should be considered as different. The test confirms that enamel etching prior to the application of a universal adhesive system depends on the selected acid etchand product.
