Masked stereolithography of hydroxyapatite bioceramic scaffolds through an integrative approach: From powder tailoring to evaluation of 3D printed parts properties

In this paper, the tailoring of hydroxyapatite powders properties for the preparation of highly hydroxyapatite-loaded photocurable organic slurries was discussed. A methodical study was conducted to investigate suspensions properties and processability to find the most outstanding formulation for the production of hydroxyapatite scaffolds by stereolithography-based additive manufacturing technique. A debinding-sintering process was designed to avoid the formation of cracks during the pyrolysis of the resin and sintering of the ceramic part. A total porosity of 35 vol. % was observed for the scaffolds with an interconnected macroporosity, which could facilitate the flow transport of nutrients necessary to maintain living cells. A compression strength of 4.9±0.3 MPa was obtained for the specimens printed diagonally (45º to the printing stage surface). A slow degradation rate was shown for the printed parts mainly due to the high degree of crystallinity and the intrinsic stability of the hydroxyapatite phase. Our findings indicate that the tailoring of hydroxyapatite powders is needed for better processability as filler in photocurable suspensions. Moreover, it was demonstrated the feasibility of printing hydroxyapatite parts showing promising results for their application in surgery in the case of minor or non-load bearing implants requiring slow resorption properties.

Получение наночастиц гидроксиапатита из естественных зубов

Hydroxyapatite is the most important bio ceramic, due to its structure and chemical composition which is similar to bone and teeth. In this study, hydroxyapatite nanoparticles were prepared from natural teeth in two stages. Initially, the nano HA particles was performed by whole tooth and in the second stage, the tooth was divided into dentine and root and HA nanoparticles were prepared from both portions of teeth. At first, freshly extracted human teeth both (whole tooth and dentine and root) were calcined at 850 °C and then, the effects of stirring time, surfactant and different temperatures were investigated. The XRD results confirmed that, the existence of hydroxyapatite phase in all samples. The phosphate bonding groups of PO43- at 1470 cm-1 and 669 cm-1 was confirmed by FTIR results. The FESEM results showed that, hydroxyapatite nano particle with the range of 29–46 nm at stirring time of 36 h with the addition of CTAB as a surfactant at 850 °C was obtained without agglomeration and good dispersion.

Synthesis and Preliminary Characterization of Modified 45s5 Bioglasses

"The study is devoted to synthesis and preliminary structural and morphological characterization of modified 45S5 glasses, in (66-x)SiO2∙27CaO∙4P2O5∙3TiO2∙xAl2O3 system, with potential applications in dentistry. The composition of the sol-gel derived samples was verified with respect to their nominal composition. The effect of partial SiO2 replacement with Al2O3 on samples structure and morphology is investigated. It was established that the Ca/P ratio is diminished in Al2O3 containing samples and that an amorphous hydroxyapatite phase similar to hydroxyapatite reported for bone tissue is formed. Keywords: bioglasses; sol-gel-synthesis; XRD; SEM; EDX. "

Silicocarnotite Synthesis and Bioactivity in Artificial Saliva Medium

The aim of this study is the synthesis and investigation of bioactive response of acrystalline silicophosphate.A monophasic silicocarnotite was elaborated by solid state reaction from a mixture of beta-tricaliciumphosphate and dicalcium silicate based on mussel shells according to the diagram of system Ca3(PO4)2–Ca2SiO4, at 65 % and 35% respectively , these starting materials are heated up to 1450 °C to obtain a monophasic silicocaronitite. The obtained result probed that the main crystalline phase which was detected and recognized in the heated sample at 1400 and 1450 °C was a well-crystallized silicocarnotite. The test of bioactivity of silicocarnotite in artificial saliva causes the appearance of a reaction layer on the materials surface after 4 hours soaking and growth up during 30 days.This layer is constituted of a biphasic mixture of Si–Ca–P–H material, silicated hydroxyapatite and hydroxyapatite phase are the mainly developing ones with increasing soaking time.The analysis and characterization of the precipitated appearing on the material surface has confirmed experimentally the in vitro bioactivity of silicocarnotite monophasic material.

Improvement of Ionic Bonding Strength and Electrochemical Corrosion Resistance of Hydroxyapatite- Calcium Phosphate Pulsed Electrochemically Deposited In-Situ Coating Through Hydroxyl Ion Treatment

Hydroxyl ion treatment of different hydroxyapatite-calcium hydrogen phosphate composite in-situ coatings synthesized through pulsed electro-deposition with varying amount of hydroxyapatite phase and degree of crystallinity were carried out with the help of highly basic solution in order to achieve a more chemically stable and corrosion resistance performance under contact with body fluid. The coatings exhibit altogether completely different behaviour in terms of bond formation, surface topography generation, phase transformation and corrosion behaviour. Detailed characterizations of formed top surface layer were carried out with the help of XRD, SEM and FTIR in order to correlate the results with their base surface characteristics. Transformation of <020> and <121> surface parallel planes of calcium hydrogen phosphate in to <002> and <112> planes of hydroxyapatite took place in all the coatings along with formation of nano-crystalline structure. Calcium-rich porous hydroxyapatite scaffold formation takes place in low current density coating which in general exhibits low stability in terms of chemical bonding strength vis-à-vis corrosion protection performance. 10 mA/cm2 coating, which come with optimum presence of hydroxyapatite phase and crystallinity post electro-deposition, showed significant improvement in terms of increasing hydroxyl and phosphate bond polarization strength of hydroxyapatite phase and the same lead to improvement in the overall corrosion resistance performance of the coating by two times. Despite of formation of highest amount of hydroxyapatite phase during hydroxyl ion treatment in 20 mA/cm2 coatings, the corrosion protection performance results are negative on account of dilution of mostly low bonding amorphous phases with high internal residual stress.

Influence of Zinc Substitution on Hydroxyapatite Structure Prepared by Chemical Precipitation Method

The zinc (Zn) substituted hydroxyapatite were synthesized using a chemical precipitation method. The chemical precursors were prepared from di-ammonium hydrogen orthophosphate, calcium oxide (CaO) derived from chicken eggshell and zinc nitrate (Zn(NO3)2). The Zn(NO3)2contents in the prepared samples were varied from 1 to 25 %wt of CaO. The Zn substituted hydroxyapatite were heated at the various temperatures from 200 to 1300 °C in the furnace with an incremental temperature of 100 °C. The crystal structure, function group and morphology of sample were analyzed by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM), respectively. The results show that the hydroxyapatite doped Zn was a hydroxyapatite phase as well as pure hydroxyapatite. The crystalline size of sample decreased with increasing the Zn content. And, the crystallinity of hydroxyapatite phase was increased following by increasing heat treatment temperature. However, the amount of Zn has the effect on phase transformation of hydroxyapatite phase after heat treatment. Zn concentration accelerates hydroxyapatite transforms to β-tricalcium phosphate phase.

Hydroxyapatite Synthesized from Waste Eggshell via Ball Milling

Hydroxyapatite was synthesized using calcium originated from waste eggshell that was reacted with phosphate obtained from diammonium hydrogen orthophosphate by ball milling technique. The samples were mixed at different time from 5 to 150 min. The structure, function group and morphology of hydroxyapatite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). The result showed that the hydroxyapatite phase was appeared after ball milling about 5 min and confirmed with FTIR results. The FE-SEM of hydroxyapatite powder was spherical shape and agglomerate. The crystallinity of hydroxyapatite was increased with increasing ball milling time. This experiment showed that the nano hydroxyapatite could synthesized from waste eggshell by ball milling technique.