Objective: To compare the effectiveness of the pretreatment with sandblasting and deproteinization with NaOCl on bond strength (SBS), in situ conversion degree (CD) of brackets in fluorotic enamel, and enamel etching pattern. Methods: A total of 90 non-carious maxillary premolars were used. The teeth were then assigned to six experimental groups according to: enamel surface (sound and fluorotic enamel); surface treatment (Regular etch with 37% phosphoric acid [RE]; 5.2% sodium hypochlorite + phosphoric acid [NaOCl + RE]; sandblasting + phosphoric acid [sandblasting + RE]). After storage in distilled water (37°C/24h), the specimens were tested at 1 mm/min until failure (SBS). Enamel-resin cement interfaces were evaluated for CD using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data from SBS and in situ CD values were analyzed using ANOVA two-away and Tukey test (α=0.05). The enamel etching pattern was evaluated only qualitatively. Results: For sound enamel, RE showed the highest SBS values, when compared to NaOCl + RE and Sandblasting + RE groups (p< 0.01). Regarding CD, only NaOCl + RE significantly compromised the mean DC, in comparison with other groups (p= 0.002). For fluorotic enamel, the Sandblasting + RE group significantly increased the mean SBS values, in comparison with RE group (p= 0.01) and no significant change was observed for CD (p> 0.52). Conclusions: The application of NaOCl or sandblasting associated to phosphoric acid improved the SBS of the brackets in fluorotic enamel without compromising the CD of the resin cement, with improving of enamel interprismatic conditioning.

SUMMARY Purpose: To evaluate the effect of application time and viscosity of meta-phosphoric acid (MPA) and ortho-phosphoric acid (OPA) on the push-out resin-dentin bond strength (PBS) and nanoleakage (NL) at the adhesive-root dentin interface. Methods and Materials: Ninety-six roots of premolars were endodontically prepared and randomly assigned into groups according to the (i) acid (OPA and MPA), (ii) viscosity (gel and liquid), and (iii) application time (7 and 15 seconds). Fiber posts were cemented to the roots, which were then transversally sectioned into serial slices. The slices (cervical, medium, and apical) were subjected to PBS or NL. Analysis of the dentin etching pattern was performed using scanning electron microscopy (SEM). The PBS (MPa) and NL (%) data were subjected to three-way repeated-measures analysis of variance (ANOVA) and Tukey’s test (α=0.05). Results: The cross-product interaction was significant for both PBS and NL (p&lt;0.001). No significant difference in the PBS was observed with the use of OPA compared to MPA (p&gt;0.05). Higher PBS values were observed in the groups etched for 15 seconds compared to 7 seconds, regardless of the acid, viscosity, or root third (p&lt;0.05). Lower NL was observed for MPA etching when compared to OPA etching (p&lt;0.05), and these values were not affected by increasing the application time or acid viscosity (p&gt;0.05). A more pronounced etching pattern was observed with OPA than MPA regardless of the acid viscosity. Conclusion: The use of 40% meta-phosphoric acid promoted adequate bond strength without increasing dentin demineralization or void spaces in the hybrid layer.

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La primera edición de Procesos de laboratorio en Mecánica Dental se crea con la intención de brindar al lector herramientas fundamentales en la fase de aprendizaje y momento de ejecución de los procesos de laboratorio más relevantes en el área; está fundamentado en literatura científica tomada de bases de datos confiables y permite al lector tener una guía de investigación profunda que amplía la visión del conocimiento investigativo y genera un elevado criterio académico.

Concrete is a composite material, composed of cement, sand, gravel and water, reinforced with steel bars or mesh. It is used for the construction of infrastructure assets such as airports, dams, ports, bridges and road ways. Polymer concrete is a relative new material containing a thermosetting resin (instead of water) displaying improved mechanical strength, low permeability, greater corrosion resistance and higher durability. It is employed for new construction and old concrete reparation in the chemical, food, fertilizer, mine and civil industries. Polymer concrete pipe specimens, reinforced with glass-fibers were prepared and exposed in a salt spray (fog) chamber, operating with a NaCl solution, following ASTM standard B-117-11. The deterioration effects were assessed by testing the physical and mechanical properties, before and after the exposure in the spray chamber, in accordance with standard ASTM D3039-2013. Corrosion resistance was evaluated applying ASTM standard C876-2013. The result of this work are presented, illustrated and discussed.