Enori Gemelli

Microstructure development on sintered Ti/HA biocomposites produced by powder metallurgy

Titanium-based composites with in-situ calcium and phosphor phases were prepared by powder metallurgy processing with titanium and hydroxyapatite (HA) powders. The mixtures were performed in a friction mill with alcohol for 5 hours, dried in a rotating evaporator, pressed at 600 MPa and sintered at 1200 oC for 2 hours in argon atmosphere. Crystal phases of the as-fabricated composite are found to be, α-Ti, CaTiO3, Ca3(PO4)2 and TixPy phase(s). The analyses revealed that titanium particles were covered with a compact layer of TixPy and CaTiO3 phases, which resulted from the decomposition of HA into CaTiO3 and β-Ca3(PO4)2 at approximately 1025 oC. Then the reactions were followed by the decomposition of β-Ca3(PO4)2, resulting in the growth of CaTiO3 layer and in the nucleation and growth of TixPy phase(s).

Thermal characterization of commercially pure titanium for dental applications

Thermal characterization of commercially pure titanium was carried out in dry air to investigate the oxidation kinetics, the oxide structures and their properties. Oxidation kinetics were performed by thermogravimetry in isothermal conditions between 300 and 750 °C for 48 hours and the oxide structures were studied by differential thermal analyses and X ray diffraction between room temperature and 1000 °C. The oxidation kinetic increases with temperature and is very fast in the initial period of oxidation, decreasing rapidly with time, especially up to 600 °C. Kinetic laws varied between the inverse logarithmic for the lower temperatures (300 and 400 °C) and the parabolic for the higher temperatures (650, 700 and 750 °C). Evidences from X ray diffraction and differential thermal analyses showed that crystallization of the passive oxide film, formed at room temperature, into anatase occurs at about 276 °C. The crystallized oxide structure is composed of anatase between 276 and 457 °C, anatase and rutile sublayers between 457 and 718 °C, and a pure layer of rutile after 718 °C. Rockwell-C adhesion tests reveled that the oxide films formed up to 600 °C have a good adhesion. Vickers indentations on the oxidized surfaces showed that the hardness of the oxide film, measured at 600 and 650 °C, is approximately 9500 MPa. At these temperatures the surface roughness varied between 0.90 and 1.30 mm.

Assessment of industrial wastes in mortar layers deposited on stainless steel sheets of sinks

This work deals with the properties of alternative mortars destined to strengthen metal sheets of sinks. The performance of these mortars was compared to that of a basic mortar made of cement, sand, and water, named standard mortar (SM). One of these mortars, named alternative mortar 2 (AM2), and composed of cement, textile residue, polyurethane, polypropylene fibers and water, was developed recently to replace the current one, named alternative mortar 1 (AM1), composed of cement, sand, polystyrene, polypropylene fibers and water. These mortars were manufactured and aged in a room in atmospheric environment for 7, 14, 28, 60 and 90 days, either with or without initial drying in a furnace. After cure of 90 days the flexion strength stress of the SM, AM1 and AM2 mortars was 5.21, 3.84, and 1.42 MPa, respectively. The SM and AM1 mortars were constituted of C-S-H phases, Ca(OH)2, SiO2, AFm and AFt (monossulphate/ettringite) phases. The AM2 mortar presented, apart from the compounds mentioned above, CaCO3. This compound is from the textile residue that is composed essentially of CaCO3 and Ca(OH)2. The reduction in flexion strength of AM1 mortar, compared to SM mortar, is caused by the polystyrene whereas the lowering mechanical strength of the AM2 is due to both polyurethane and textile residue. Even so, its mechanical strength is acceptable because the flexion strength stress required for the industrial application is 1.0 MPa.

Characterization of Three Calcium Phosphate Microporous Granulated Bioceramics

The calcium phosphate microporous bioceramics, and hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) biphasic compositions, in the granular form of microporous biomaterials, are research themes and present potential biomedical applications in rebuilding and repairing maxillofacial bone and tooth structure and in orthopedic applications. This is associated with microstructural characteristics of biocompatibility and bioactivity and osteoconductivity properties that these biomaterials offer when applied in vivo or in simulated environment. Another differential point of these biomaterials is the solubilization capacity that they present when applied in the biological environment. These compositions of calcium phosphates (hydroxyapatite matrix and/or β-tricalcium phosphate) allow for the gradual release of calcium and phosphate ions for the biological environment, which are absorbed and promote the formation of new bone tissue. These materials are also promising in applications in the field of traumatology as in the repair of traumatized bone tissue and drugs controlled release and bone structure treatments. The favorable results of these biomaterials as bone reconstruction matrix and drugs controlled release are associated with crystallographic characteristics, morphology, surface and solubility that these biomaterials present when in contact with body fluids. This work aimed to describe three types of calcium phosphate microporous granulated biomaterials. The biomaterials used were provided by the Biomaterials Group from Universidade do Estado de Santa Catarina - UDESC and are: hydroxyapatite, β-tricalcium phosphate and biphasic composition 60% hydroxyapatite/40% β-tricalcium phosphate. The Scanning Electron Microscopy technique (SEM) was used for carrying out the morphological characterization and microstructure studies of granulated biomaterials. The X-Ray Diffractometry (XRD) served for characterization of crystalline phases. Arthur Method was used for determining open porosity and hydrostatic density of biomaterials. The BET technique served to support determination of the surface area of microporous granulated biomaterials. The results are encouraging and show that these biomaterials present promising morphological characteristics and microporous microstructure as wettability and capillarity. These characteristics may contribute to biomaterial osteointegration by new tissue, bone formation and mineralization process.

Synthesis and Characterization of Nanostructured Ceramic Powders of Calcium Phosphate and Hydroxyapatite for Dental Applications

In the last decades many investigations have been oriented toward the development of nanostructured biomaterials such as calcium phosphate ceramics, particularly those composed of stoicheiometric hydroxyapatite (Ca10(PO4)6(OH)2) and a-and β- tricalcium phosphate (Ca3(PO4)2), which present chemical and crystallographic similarities with hard tissues (bones and teeth). Because of these characteristics, these materials can be used for reconstitution and regeneration of bone tissues. The odontological and biomedical applications are still limited due to their brittle behaviour. This study was focused in the synthesis and characterization of a bone matrix of calcium phosphate (β-TCP) and hydroxyapatite (HAP-101 e HAp-201). The results presented here are related to the morphological characterization of nanostructured powders from scanning electron microscopy viewpoint. X-ray diffraction was used to identifier the present phases in the powders and the infrared spectrometry (FTIR) was used to analyse OH bonds from hydroxyapatite and PO4 from calcium phosphates.

Cell adhesion on different titanium-coated surfaces

Titanium (Ti) is a biocompatible material, and calcium phosphate coating on titanium is commonly applied in order to obtain faster osseointegration around metallic implant. Osteoblast adhesion on three different Ti surfaces was evaluated. The investigated surfaces were commercially pure Ti (cp Ti), Ti coated with sodium titanate (Na-Ti), and Na-Ti followed by octacalcium phosphate coating (Ti-OCP) done by immersion in a calcium and phosphate-rich solution. The studied materials exhibited different morphology and composition. However, all the surfaces promoted cellular adhesion and showed cytocompatibility. No statistically significant difference was observed among the evaluated samples in relation to the number of cells.

Synthesis and characterization of nanostructured ceramics powders for biomedical applications

Nanostructured materials have been largely studied in the last few years because they have a great potential to applications in different fields like physics, chemistry, biology, mechanic and medicine. Synthesis and characterization of nanostructured materials is a subject of great interest involving science, market, politicians, government and society. The nanostructured materials are in demand in biomedical area, mainly the bioceramics composed of calcium phosphates (Ca/P), which have an excellent biocompatibility and mineralogical characteristics similar to those of bones. The aim of this work was to optimize the method of powder synthesis of nanostructured calcium phosphate and of nanocomposites composed of calcium phosphate//SiO2n, containing 5, 10 and 15% (in volume) of nanometric silica (SiO2n). The results are expressed according to the method of synthesis, mineralogical and morphological characterization, and thermal behavior for the different compositions of the nanostructured powder synthesized.

Elaboration and characterization of nanostructured biocements for biomedical applications

Biocements formed from the composition Ca/P have been studied and developed since 1983. These biomaterials are promissing and have aroused great interest to biomedical surgery applications, fixation of prostheses and filling and reconstruction of bones. They can be employed as an element of load to fix implant and bone structure. In addition, biocements are easily shaped during surgical processes and favor early bone habitation, absorption, osseointegration, and osteoconduction of bone structure into the microstructure of the biocement thus favoring regeneration and reconstruction of bone tissue. This paper aims to develop biocements formed from calcium phosphate through the aqueous precipitation method by means of the dissolution-precipitation reaction, which involves solid/ liquid phase of CaO and phosphoric acid to form the calcium phosphate. The biocements investigated were synthesized when the molar ratios of Ca/P = 1.4, 1.5, 1.6, 1.7 and 1.8. The present results indicate that the aqueous precipitation method allowed nanostructured powder of calcium phosphate to form. Thermal treatment at 1300 °C for 2 hours provided biocements formed from calcium phosphate and hydroxyapatite. The study of hydration behaviour from 1 to 28 days in a solution, which contained 0.4% of sodium phosphate, emphasized phase modification and the presence of a microporous microstructure made of crystalline fibers. It was found that the shape and size of the crystalline fiber had a direct influence on the resulting mechanical properties. Investigating more carefully the behaviour of the specimens with a Ca/P molar ratio of 1.5, there was an increase in the strength value under compression as a function of time so that it reached the maximum value of strength ±45 MPa to specimens that had been hydrated for 28 days.

Elaboration of a triphasic calcium phosphate and silica nanocomposite for maxillary grafting and deposition on titanium implants

Abstract A hydroxyapatite and tricalcium phosphate nanocomposite containing 5% silica was developed for dental applications. The biomaterial was prepared by one-step synthesis via the wet route. The resulting dry material consisted of hydrated calcium phosphate agglomerates with sizes of up to 200 μm. The presence of silica was found to lower the phase transformation temperature of the calcium phosphates and increase the open porosity of the biomaterial compared to that of hydroxyapatite. The hydrated calcium phosphate transformed into hydroxyapatite (HA) and beta tricalcium phosphate (TCP) at approximately 682 °C. After 2 h of calcination at 900 °C, the volume ratios of HA and TCP in the nanocomposite were 84 and 16%, respectively. The open porosity in the triphasic nanocomposite and in the HA was 46.35% and 41.52%, respectively, after 3 h of sintering at 1 100 °C. Samples of grade 2 titanium were sandpapered and etched with an acid solution of HCl/H2SO4 prior to deposition of the calcined nanocomposite. The particles were deposited homogeneously and reduced the contact angle of the titanium surface.

Hydration study from different calcium phosphate biocements with microstructure and nanostructure.

Important features of biocements include easy molding and good wettability, hydration, and setting time during its application in biological tissue. Interest in calcium phosphate biocements is directly related to its characteristics of bioactivity, biocompatibility, and crystallographic similarity to bone apatite. This experimental study aimed to understand hydration behavior of calcium phosphate biocements with microstructure and nanostructure, with molar ratios Ca/P = 1.5; 1.6; 1.67; and 1.7 and hydration times of 5 and 30 min. The hydration tests were performed on the same solid/liquid ratio for the four Ca/P compositions. The morphology was observed via scanning electron microscopy and phases were identified with help from X-ray diffraction. The biocements showed similar effects of hydration and gelling for the periods of 5 and 30 min. The results show that these biocements can offer favorable wettability, hydration, and easy molding during the surgical procedure, which could be an innovation in implant fixation and bone tissue repair.