J. A. Delgado

α-Tricalcium phosphate cements modified with β-dicalcium silicate and tricalcium aluminate: Physicochemical characterization, in vitro bioactivity and cytotoxicity

Biocompatibility, injectability and in situ self-setting are characteristics of calcium phosphate cements which make them promising materials for a wide range of clinical applications in traumatology and maxillo-facial surgery. One of the main disadvantages is their relatively low strength which restricts their use to nonload-bearing applications. α-Tricalcium phosphate (α-C3P) cement sets into calcium-deficient hydroxyapatite (CDHA), which is biocompatible and plays an essential role in the formation, growth and maintenance of tissue-biomaterial interface. β-Dicalcium silicate (β-C2S) and tricalcium aluminate (C3A) are Portland cement components, these compounds react with water to form hydrated phases that enhance mechanical strength of the end products. In this study, setting time, compressive strength (CS) and in vitro bioactivity and biocompatibility were evaluated to determine the influence of addition of β-C2S and C3A to α-C3P-based cement. X-ray diffraction and scanning electron microscopy were used to investigate phase composition and morphological changes in cement samples. Addition of C3A resulted in cements having suitable setting times, but low CS, only partial conversion into CDHA and cytotoxicity. However, addition of β-C2S delayed the setting times but promoted total conversion into CDHA by soaking in simulated body fluid and strengthened the set cement over the limit strength of cancellous bone. The best properties were obtained for cement added with 10 wt % of β-C2S, which showed in vitro bioactivity and cytocompatibility, making it a suitable candidate as bone substitute.

β-Dicalcium silicate-based cement: Synthesis, characterization and in vitro bioactivity and biocompatibility studies

β-dicalcium silicate (β-Ca₂ SiO₄, β-C₂ S) is one of the main constituents in Portland cement clinker and many refractory materials, itself is a hydraulic cement that reacts with water or aqueous solution at room/body temperature to form a hydrated phase (C-S-H), which provides mechanical strength to the end product. In the present investigation, β-C₂ S was synthesized by sol-gel process and it was used as powder to cement preparation, named CSiC. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid solutions and human osteoblast cell cultures for various time periods, respectively. The results showed that the sol-gel process is an available synthesis method in order to obtain a pure powder of β-C₂ S at relatively low temperatures without chemical stabilizers. A bone-like apatite layer covered the material surface after soaking in SBF and its compressive strength (CSiC cement) was comparable with that of the human trabecular bone. The extracts of this cement were not cytotoxic and the cell growth and relative cell viability were comparable to negative control.

Sistemas de Liberación Controlada de Fármacos a Partir de Materiales para la Restauración del Tejido Óseo

Nowadays, two of the most important problems are the high incidence of bone infections and the inflammatory response of the human organism when an implant is used. For this reason, the inclusion of drugs in materials for bone restoration is an interesting and promising approach to solve this problem. On this paper, drug delivery systems from bone restoration materials making little modifications to classic materials such as calcium phosphate cements, PMMA acrylic cements and coating metals were prepared, characterized and evaluated. All the prepared matrixes showed no-interaction between main components of formulation allowing the composition to lead the behavior of drug profile. The modifications made to classic bone materials on hydrophilicity and porosity, two important characteristics, helped to improve the drug delivery capacity. The ending results of delivery moved between 40-95 % in different time ranges according to composition which allows different possible application of these materials.

Aplicaciones de los Vidrios de Fosfato de Calcio en el Desarrollo de Composites Bioactivos para la Sustitución del Tejido Óseo

Nowadays bioactive glasses are frequently used for bone tissue replacement. In this work two new different calcium phosphate glasses were prepared and characterized. The chemical compositions were (in mol%): 11Na2O-44.5P2O5-44.5CaO (Bv11) and 6Na2O-44.5P2O5-44.5CaO-5TiO2 (G5). Both materials were silanyzed and characterized by Differential Thermal Analysis (DTA), Transformed Fourier-Infrared Spectroscopy (FTIR) and Dilatometry. The bioglasses prepared were also used as filler of conventional polymethylmetacrylate (PMMA) bone cement and it’s bioactive behavior explored by soaking composites in Simulated Body Fluid (SBF). The samples of modified cements exhibited significant morphological surface changes. Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and Field Emission-SEM (FE-SEM) analysis confirmed the formation of calcium phosphate precipitates on the surface of the cement. The amount of precipitates was higher for cements which contained Bv11 as filler than those loaded with G5 glass particles. These results revealed that the higher bioactivity of the cement load with Bv11 could be related with the higher solubility of this glass.

Preparation and characterization of hydrophilic composites AA/EPMA loaded with hydroxyapatite.

Copolymeric composites of acrylamide (AA) and 2,3-epoxypropyl methacrylate (EPMA) with hydroxyapatite (HA) load were studied. Swelling studies reports an anomalous or non-Fickian behavior following a good fitting to a pseudo second order mathematical treatment (α = 0.05, p < 0.0001). The composites showed a strong dependence on pH, related with the variations in the swelling behavior. The addition of load induces a diminution of swelling capacity and an increase of diametric tensile strength (DTS) ranging between 20 and 90 kPa. The calorimetric experiments showed two steps at 78°C and 255°C assigned to water loss and samples Tg. The drug control released was adjusted to a two-term equation obtaining a diffusion coefficient around 10(-5) cm(2) /s. The samples showed a significant bioactivity in vitro and it was certified by SEM, EDS and surface area calculus.

Different Synthesis Routes for Hydroxyapatite Nanoparticles by Mechanical Stirring

Nanosized hydroxyapatite (HA) with crystallinity and composition similar to bone apatite has been widely investigated in the last years, due to their excellent biocompatibility in bone replacement applications. This bioceramic can be synthesized by many wet chemical and mechanochemical methods. In this paper, nanosized hydroxyapatite powders were synthesized by two wet chemical routes using mechanical stirring method. The first route was used for HA synthesis from CaCl2.2H2O and Na3PO4.12H2O solutions and the second route was from Ca (OH)2 and H3PO4 solutions. The synthesized HA nanoparticles were characterized by Dynamic Light Scattering, BET Surface Area analysis, X-ray Diffraction, Infrared Spectroscopy, chemical analysis and Scanning Electron Microscopy. The results indicated that HA nanoparticles were successfully synthesized by both wet chemical precipitation routes and all powders presented a Ca/P ratio similar to stoichiometric HA, nanoneedles morphology and single HA crystalline phase.

Pre-prosthetic Remodeling of Alveolar Ridge Using Calcium Phosphate Biomaterials

Maxilla or mandible alveolar ridge defects are commonly a sequel to dental extractions when preventive treatment of atrophy of the maxillary bone (ABM) is not performed. In order to achieve bone reconstruction of the reabsorbed alveolar ridge, oral surgery is needed. The aim of this paper is to study the combine application in the alveolar ridge remodeling of dental biomaterials Biograft-G®, MEMBRACEL®-O and Tisuacryl®. Eleven patients affected by maxillary alveolar bone atrophy were treated. The evaluation was performed at 7 days and 6 months from surgery. At seven days, no cases of infection were observed, but the presence of edema was reported in two cases and granules exfoliation in one of them. No ARs were observed. At 6 months, 100% of patients achieving a Success in the reconstruction of atrophic alveolar ridge. It is concluded that the combine application of dental biomaterials is effective and safe for the pre-prosthetic alveolar ridge remodeling.

Effect of Sonochemical Technique on the Morphology and Crystallinity of Hydroxyapatite Nanoparticles

Hydroxyapatite (HA) is the main mineral component of bones and teeth, and for this reason its synthetic analogous has been used with excellent clinical results as bone substitute. The biological apatite is typified as a poorly crystalline carbonate apatite (CHA) formed by nanosized particles with a great superficial area. This work aimed to study the influence of ultrasound technique on the morphology and crystallinity of nanoHA synthesized by chemical precipitation method. The nanoHA particles were obtained from CaCl2·2H2O and Na3PO4·12H2O raw solutions and a powerful ultrasonic sound (UP400S) was used at different conditions during the synthesis. X-ray Diffraction, Infrared spectroscopy, Chemical Analysis and Scanning Electron Microscopy were used to characterize the synthesized nanoHA particles. The results indicated that HA nanoparticles with nanorods morphology were obtained in all conditions. By Scherrer`s formula, the crystallite size was determined and it was found that the increasing in ultrasound amplitude enhances the nanoparticles crystallinity.

Sintering Behavior of Nanostructured Hydroxyapatite Ceramics

The synthesis of nanoparticles appropriate for the preparation of nanostructured hydroxyapatite ceramics intended for bone repairs and regeneration is an interesting field of biomaterials research today. In this work nanoparticles of hydroxyapatite were obtained by the precipitation method using conventional magnetic stirring (A) and ultra turrex homogenizer (T1) accompanied with surfactant (T2) and dispersant agents (T3). In all cases, powders with nanometric dimensions were obtained and the unique calcium phosphate phase detected was hydroxyapatite (HAp). The powders sintering behaviour was studied. The ceramics obtained from powders prepared by magnetic stirring (A) showed the best values of final density (96.7 %) which it was in agreement with the lowest temperature of the beginning of shrinking (648.6 °C) during sintering determined by dilatometry. Nanostructured nature of these ceramics was confirmed by Scanning Electron Microscopy (SEM).

Cementos Biomédicos de Fosfato Tricálcico Reforzados con Silicatos y Aluminatos de Calcio-Preparación, Caracterización y Estudios de biodegradación

The combination of in situ self-setting and biocompatibility makes calcium phosphate cements highly promising materials for a wide range of clinical applications. However, its low strength limits its use to only non-stress applications. α-Tricalcium phosphate (α-TCP) cement sets into calcium-deficient hydroxyapatite (CDHA), which is a biocompatible compound and can induce osteointegration. β-Dicalcium silicate (β-C2S) and tricalcium aluminate (C3A) are Portland cement components, these compounds react with water to form hydrated phases that enhance mechanical strength of the end products. In this investigation, were prepared α-TCP cements modified with β-C2S and C3A. α-TCP powder was prepared through acid-base method, β-C2S and C3A were synthesized by sol-gel method. Materials were characterized chemical and physically. Biodegradability was studied by soaking the materials in simulated body fluid (SBF) at 37°C for 7 days. All cements exhibited long setting times and excellent setting temperature. T (100% α-TCP) and TS10 (10%-β-C2S) were converted to CDHA after 7 days soaking in SBF and their compressive strength were comparable to that of trabecular bone. TA10 (10%-C3A) was only partly converted to CDHA and showed the lowest compressive strength.