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Calcium phosphate (CaP) scaffolds doping with therapeutic ions are one of the focuses of recent bone tissue engineering research. Among the therapeutic ions, strontium stands out for its role in bone remodeling. This work reports a simple method to produce Sr-doped 3D-printed CaP scaffolds, using Sr-doping to induce partial phase transformation from ß-tricalcium phosphate (ß-TCP) to hydroxyapatite (HA), resulting in a doped biphasic calcium phosphate (BCP) scaffold. Strontium carbonate (SrCO3) was incorporated in the formulation of the 3D-printing ink, studying ß-TCP:SrO mass ratios of 100:0, 95:5, and 90:10 (named as ß-TCP, ß-TCP/5-Sr, and ß-TCP/10-Sr, respectively). Adding SrCO3 in the 3D-printing ink led to a slight increase in viscosity but did not affect its printability, resulting in scaffolds with a high printing fidelity compared to the computational design. Interestingly, Sr was incorporated into the lattice structure of the scaffolds, forming hydroxyapatite (HA). No residual SrO or SrCO3 were observed in the XRD patterns of any composition, and HA was the majority phase of the ß-TCP/10-Sr scaffolds. The addition of Sr increased the compression strength of the scaffolds, with both ß-TCP/5-Sr and ß-TCP/10-Sr performing better than the ß-TCP. Overall, ß-TCP/5-Sr presented higher mineralized nodules and mechanical strength, while ß-TCP scaffolds presented superior cell viability. The incorporation of SrCO3 in the ink formulation is a viable method to obtain Sr-BCP scaffolds. Thus, this approach could be explored with other CaP scaffolds aiming to optimize their performance and the addition of alternative therapeutic ions.

RESUMO

OBJECTIVES: To synthesize and characterize a novel dentin adhesive containing Beta-Tricalcium Phosphate (ß-TCP) nanoparticles and test its ability to reduce dentin permeability (dP). METHODS: Experimental adhesives were prepared by mixing Bis-GMA, TEGDMA, HEMA (50/25/25 wt.%), photo-initiators, and inhibitors. The following groups were tested: Experimental adhesives without ß-TCP (Exp.); with 10 wt.% ß-TCP (Exp.10 wt.% ß-TCP); with 15 wt.% ß-TCP (Exp.15 wt.% ß-TCP), Scotchbond Multi-Purpose (SBMP) and Clearfil SE Protect Bond (CFPB). Degree of conversion (DC%, 10 and 20 s); Flexural Strength (FS), Knoop Hardness (KHN), and Cell Viability (OD%) tests were performed. dP was evaluated by hydraulic conductance, using human dentin disks (n=12), at three-time intervals: post-EDTA (T0); post-treatment (T1); and post-erosion/abrasion cycling (T2). Data were statistically analyzed (α=0.05). RESULTS: For all groups, exposure time for 20 s presented a higher DC% than for 10 s. For FS, filled adhesives did not differ from unfilled and from CFPB. Experimental adhesives did not differ among them and showed lower KHN than the commercial products. Cell viability did not differ among adhesives, except Exp. 15 wt.%, which showed lower OD% than Exp., Exp. 10% and, CFPB. For dP, only Exp.10 and 15 wt.% ß-TCP did not present difference between the times T1 and T2. After cycling, Exp.10 wt.% ß-TCP presented lower permeability than Exp. and CFPB. CONCLUSIONS: The incorporation of 10 wt.% ß-TCP nanoparticles into the resin-based dental material did not affect its mechanical properties and biocompatibility, and promoted the greatest reduction in dentin permeability, sustaining this effect under erosive/abrasive challenges. CLINICAL SIGNIFICANCE: A novel resin-based dental material containing ß-TCP nanoparticles was able to reduce dentin permeability, maintaining its efficacy after erosive/abrasive challenges. The synthesized material did not affect dental pulp cell viability and might be promising for other conditions that require dental remineralization, such as tooth wear and dental caries.

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The objective of this study was to investigate the osteogenic and antimicrobial effect of bioactive glass S53P4 incorporated into ß-tricalcium phosphate (ß-TCP) scaffolds in vitro and the bone neoformation in vivo. ß-TCP and ß-TCP/S53P4 scaffolds were prepared by the gel casting method. Samples were morphologically and physically characterized through X-ray diffraction (XRD) and scanning electron microscope (SEM). In vitro tests were performed using MG63 cells. American Type Culture Collection reference strains were used to determine the scaffold's antimicrobial potential. Defects were created in the tibia of New Zealand rabbits and filled with experimental scaffolds. The incorporation of S53P4 bioglass promotes significant changes in the crystalline phases formed and in the morphology of the surface of the scaffolds. The ß-TCP/S53P4 scaffolds did not demonstrate an in vitro cytotoxic effect, presented similar alkaline phosphatase activity, and induced a significantly higher protein amount when compared to ß-TCP. The expression of Itg ß1 in the ß-TCP scaffold was higher than in the ß-TCP/S53P4, and there was higher expression of Col-1 in the ß-TCP/S53P4 group. Higher bone formation and antimicrobial activity were observed in the ß-TCP/S53P4 group. The results confirm the osteogenic capacity of ß-TCP ceramics and suggest that, after bioactive glass S53P4 incorporation, it can prevent microbial infections, demonstrating to be an excellent biomaterial for application in bone tissue engineering.

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Lanthanide-based beta-tricalcium phosphate (ß-TCP) upconversion nanoparticles are exploited as a non-viral vector for imaging guided-gene therapy by virtue of their unique optical properties and multi-modality imaging ability, high transfection efficiency, high biocompatibility, dispersibility, simplicity of synthesis and surface modification. Ytterbium and thulium-doped ß-TCP nanoparticles (ßTCPYbTm) are synthesized via co-precipitation method, coated with polyethylenimine (PEI) and functionalized with a nuclear-targeting peptide (TAT). Further, in vitro studies revealed that the nanotheranostic carriers are able to transfect cells with the plasmid eGFP at a high efficiency, with approximately 60% of total cells producing the fluorescent green protein. The optimized protocol developed comprises the most efficient ßTCPYbTm/PEI configuration, the amount and the order of assembly of ßTCPYbTm:PEI, TAT, plasmid DNA and the culturing conditions. With having excellent dispersibility and high chemical affinity toward nucleic acid, calcium ions released from ßTCPYbTm:PEI nanoparticles can participate in delivering nucleic acids and other therapeutic molecules, overcoming the nuclear barriers and improving the transfection efficacy. Equally important, the feasibility of the upconversion multifunctional nanovector to serve as an effective contrast agent for imaging modality, capable of converting low-energy light to higher-energy photons via a multi-photons mechanism, endowing greater unique luminescent properties, was successfully demonstrated.

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The crystalline indexes obtained through infrared spectroscopy (CIIR) and X-ray diffraction (CIXRD) were used to analyze the structural changes of dentin and enamel in human teeth when subjected to heat treatments between room temperature (25 °C) to 1200 °C in atmospheric air and argon. Thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses of sound powders were also used to support the analysis. As the temperature increased, the CIXRD increased exhibiting a behavior like that of the crystal grain size, and the CIIR increased until the ß-TCP phase appeared. These results indicated that the CIIR was more variable to structural changes than the CIXRD.

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El propósito de este estudio fue de evaluar la técnica quirúrgica propuesta para estudios de resección y reconstrucción mandibular en modelos experimentales en conejos. Se utilizaron 7 conejos neozelandeses (Orictolagus cuniculus), en los cuales se realizó la resección del cuerpo mandibular izquierdo, una vez asegurada la movilidad de los segmentos, se reconstruyó con placa de osteosíntesis de titanio de 1,5 mm y tornillos monocorticales de 5 mm, en la zona resecada se fijó un bloque de beta fosfato tricálcico y estabilizado con tornbillo de 1,2 mm. Se sacrificaron los animales a los 2 meses. Todos los animales sobrevivieron al procedimiento y se pudo llevar a cabo la resección y reconstrucción en todos ellos. No se presentaron signos ni síntomas de infección en el sitio quirúrgico mientras duró el experimento. El tiempo promedio de cirugía fue de 68 minutos. El peso promedio de los animales fue de 3925 g, la pérdida promedio de peso fue de 2,03 %. No se realizó eutanasia de ningún animal por motivos de sufrimiento. Al examen macroscópico de las muestras extraídas se observó la presencia de todos los elementos de osteosíntesis en posición, así como continuidad de la estructura ósea casi en su totalidad en la superficie . La utilización de conejos en modelos de reconstrucción maxilofacial es un modelo probado debido a la similitud de los procesos reparativos, su facilidad de manipulación y cuidados. El modelo propuesto representa una alternativa más cercana a los procesos reconstructivos en cirugía resectiva maxilofacial, debido a que somete los injertos a las fuerzas propias de la masticación y de la función orofacial.

The purpose of this study was to evaluate the surgical technique proposed for studies of resection and mandibular reconstruction in experimental models in rabbits. Seven rabbits (Orictolagus cuniculus) were used, in which the left mandibular body was resected, once the mobility of the segments was assured, reconstructed with 1.5 mm titanium osteosynthesis plate and monocortical screws of 5 mm, in the resected area a block of beta-tricalcium phosphate was stabilized and stabilized with tornbillo of 1.2 mm. The animals were sacrificed at 2 months. All animals survived the procedure, and resection and reconstruction were performed in all of them. There were no signs or symptoms of infection at the surgical site during the experiment. The average length of surgery was 68 minutes. The average weight of the animals was 3.925 g, the average weight loss was 2.03 %. No animal was euthanized for reasons of suffering. Macroscopic examination of the extracted samples showed the presence of all elements of osteosynthesis in position, as well as continuity of the bone structure almost entirely on the surface. The use of rabbits in models of maxillofacial reconstruction is a proven model due to the similarity of the reparative processes, their ease of manipulation and care. Our proposed model represents a closer alternative to the reconstructive processes in maxillofacial resective surgery, because it subjects the grafts to the forces of chewing and orofacial function.

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