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.

Mechanical behavior of hydroxyapatite-based composites (HAp) was studied as a function of the reinforcement concentration of the quasicrystalline (QC) Al64Cu23Fe13 alloy. The synthesis of the HAp matrix was carried out by sol-gel method, while the synthesis of the QC was performed by an arc furnace with a subsequent thermal treatment. The composites were made by powder metallurgy and cold compacted to form test pieces that were sintered with a constant flow of argon. The materials were characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and Fourier transform Raman spectroscopy. The study of mechanical strength was carried through compression tests. The biocompatibility of the composites was tested using an in-vitro cytotoxicity assay. The mechanical resistance of HAp/QC composites increased with the concentration of quasicrystalline reinforcement. Young’s modulus and compressive strength increased in 43% and 21%, respectively, with a 10 wt% QC reinforcement, which demonstrates an hybrid behaviour of the composite due to the inclusion of reinforcing particles in the pores of the matrix. This composite did not show cytotoxicity at any of the QC concentrations. A fabrication route is proposed as a fast, easy and high efficiency alternative for applications in the biomedical industry because of its high scalability potential.

Introduction: Dentin hypersensitivity is a common pathology, produced by exposed dental tubules. Objectives: The aim of this study was the evaluation of the effectiveness of experimental toothpaste based on nano-hydroxyapatite (nHAP) obtained from chicken eggshell in the obliteration of dentinal tubules (DTs). Material and methods: Toothpastes with different percentages of nHAP were formulated, including 3%, 7%, and 15% of nHAP, a commercial paste, and a toothpaste without nHAP. Assays were made using healthy premolar samples (n = 50). The pastes were applied and brushed for 7 days after a first erosive cycle, then a second erosive cycle was made at 15 days. Samples were analyzed using scanning electron microscopy and confocal Raman microscopy at three times: after the first erosive cycle (T0), after applications of the pastes (T7), and after the second erosive cycle (T15). Results:The quantitative analysis of the micrographs showed a significant difference between the experimental toothpastes with respect to the controls. Moreover, there was no statistically significant difference between the experimental toothpastes at time T7. By mineral concentration analysis, the 3%-nHAP toothpaste presented a significant difference against conventional toothpaste, when evaluating mineral concentration at 7 days. Conclusions: The experimental paste is effective in obliterating DTs at concentrations of 7 and 15%, in addition to being stable over time.

El objetivo de esta revisión de literatura es identificar las diferentes fuentes de obtención de hidroxiapatita (HAP) a partir de residuos naturales con la finalidad de utilizarla como injertos óseos dentales. La hidroxiapatita se puede clasificar según sus fuentes de origen en sintética o biológica; entre las fuentes de orígenes biológicos podemos encontrar de origen animal, origen acuático, origen coralino, origen de cáscara de huevo y de origen vegetal. Se describen los diferentes tipos de síntesis disponibles en la literatura para la obtención de hidroxiapatita a partir de cada fuente natural y su comportamiento como material de relleno óseo. Las fuentes naturales para obtención de hidroxiapatita a partir de residuos orgánicos reducen el impacto ambiental (bio basura) además de tener múltiples propiedades biocompatibles con el tejido óseo humano.