Synthesis and sintered properties evaluation of calcium phosphate ceramics

The present paper describes calcination of calcium phosphate ceramics (hydroxyapatite, HA) at 200, 400, 600, 800 and 1000 °C to observe the phase change using X-ray diffraction. HA phase was found to be stable up to 600 °C and later got dissociated into other non-stoichiometric phases like tricalcium phosphate (Ca3(PO4)2 [TCP]), calcium pyrophosphate (Ca2P2O7 [CPP]) and calcium hydrogen phosphate (CaHPO4 [CHP]). TCP was found to be the major phase above 1000 °C. FTIR spectra showed the presence of various PO43− and OH− groups present in the powder. Powders compacted and sintered at 900, 1000, 1100 and 1200 °C showed an increase in density from 2.11 to 2.95 g/cm3 while biaxial flexural strength (BFS) was found to be higher (48.7 MPa) when the samples were sintered at 1100 °C and it decreased with further increase in sintering temperature.© Elsevie

Comparative study on Ti-Nb binary alloys fabricated through spark plasma sintering and conventional P/M routes for biomedical application

The main purpose of this work is to obtain homogenous, single β phase in binary Ti-xNb (x = 18.75, 25, and 31.25 at.%) alloys by simple mixing of pure elemental powders using different sintering techniques such as spark plasma sintering (pressure-assisted sintering) and conventional powder metallurgy (pressure-less sintering). Synthesis parameters such as sintering temperature and holding time etc. are optimized in both techniques in order to get homogenous microstructure. In spark plasma sintering (SPS), complete homogeneous β phase is achieved in Ti25at.%Nb using 1300 °C sintering temperature with 60 min holding time under 50 MPa pressure. On the other hand, complete β phase is obtained in Ti25at.%Nb through conventional powder metallurgy (P/M) route using sintering temperature of 1400 °C for 120 min holding time which are adopted from the dilatometry studies. Nano-indentation is carried out for mechanical properties such as Young's modulus and nano-hardness. Elastic properties of binary Ti-xNb compositions are fallen within the range of 80–90 GPa. Cytotoxicity as well as cell adhesion studies carried out using MG63, osteoblast-like cells showed excellent biocompatibility of thus developed Ti25at.%Nb surface irrespective of fabrication route

Positively charged bioactive Ti metal prepared by simple chemical and heat treatments

A highly bioactive bone-bonding Ti metal was obtained when Ti metal was simply heat-treated after a common acid treatment. This bone-bonding property was ascribed to the formation of apatite on the Ti metal in a body environment. The formation of apatite on the Ti metal was induced neither by its surface roughness nor by the rutile phase precipitated on its surface, but by its positively charged surface. The surface of the Ti metal was positively charged because acid groups were adsorbed on titanium hydride formed on the Ti metal by the acid treatment, and remained even after the titanium hydride was transformed into titanium oxide by the subsequent heat treatment. These results provide a new principle based on a positively charged surface for obtaining bioactive materials

Osteoinduction on acid and heat treated porous Ti metal samples in canine muscle.

Samples of porous Ti metal were subjected to different acid and heat treatments. Ectopic bone formation on specimens embedded in dog muscle was compared with the surface characteristics of the specimen. Treatment of the specimens by H2SO4/HCl and heating at 600 °C produced micrometer-scale roughness with surface layers composed of rutile phase of titanium dioxide. The acid- and heat-treated specimens induced ectopic bone formation within 6 months of implantation. A specimen treated using NaOH followed by HCl acid and then heat treatment produced nanometer-scale surface roughness with a surface layer composed of both rutile and anatase phases of titanium dioxide. These specimens also induced bone formation after 6 months of implantation. Both these specimens featured positive surface charge and good apatite-forming abilities in a simulated body fluid. The amount of the bone induced in the porous structure increased with apatite-forming ability and higher positive surface charge. Untreated porous Ti metal samples showed no bone formation even after 12 months. Specimens that were only heat treated featured a smooth surface composed of rutile. A mixed acid treatment produced specimens with micrometer-scale rough surfaces composed of titanium hydride. Both of them also showed no bone formation after 12 months. The specimens that showed no bone formation also featured almost zero surface charge and no apatite-forming ability. These results indicate that osteoinduction of these porous Ti metal samples is directly related to positive surface charge that facilitates formation of apatite on the metal surfaces in vitro

TF-XRD diffraction patterns of the surfaces of the porous Ti metal specimens subjected to various treatments described in Table 1, Un: Untreated, Ht: heat treated, Ac: Mixed acid treated, Ac-Ht: Mixed acid and heat treated, Na-0.5H-Ht: NaOH: NaOH, 0.5 mM HCl and heat treated, Na-50H-Ht: NaOH, 50 mM HCl and heat treated.

<p>Ti: Titanium, TH: Titanium hydride, R: Rutile, A: Anatase.</p

Distribution of pore diameters on a full scale (a) and expansions (b), (c) for the porous Ti metals subjected to various treatments given in Table 1, as measured by Hg penetration porosimetry, where the x-axis is pore diameter, and the y-axis is log differential volume of Hg that penetrated into the pores of the sample per unit weight.

<p>Un: Untreated, Ht: heat treated, Ac: Mixed acid treated, Ac-Ht: Mixed acid and heat treated, Na-0.5H-Ht: NaOH: NaOH, 0.5 mM HCl and heat treated, Na-50H-Ht: NaOH, 50 mM HCl and heat treated.</p

Optical microscope images of non-decalcified histological sections of porous Ti metals subjected to various treatments given in Table 1, after implantation in dog back muscle for 6 (a) and 12 (b) months.

<p>Scale bar: 1 mm. Un: Untreated, Ht: heat treated, Ac: Mixed acid treated, Ac-Ht: Mixed acid and heat treated, Na-0.5H-Ht: NaOH: NaOH, 0.5 mM HCl and heat treated, Na-50H-Ht: NaOH, 50 mM HCl and heat treated.</p

New bone growth rate on porous Ti metal specimens subjected to various treatments described in Table 1, evaluated 6 and 12 months after implantation.

<p>*: p<0.05 vs. Un, Ht, Ac and Na-0.5H-Ht. #: p<0.05 vs. Un, Ht and Ac. Un: Untreated, Ht: heat treated, Ac: Mixed acid treated, Ac-Ht: Mixed acid and heat treated, Na-0.5H-Ht: NaOH: NaOH, 0.5 mM HCl and heat treated, Na-50H-Ht: NaOH, 50 mM HCl and heat treated.</p

SEM images of inner walls of the pores of the porous Ti metal specimens subjected to the various treatments described in Table 1.

<p>Un: Untreated, Ht: heat treated, Ac: Mixed acid treated, Ac-Ht: Mixed acid and heat treated, Na-0.5H-Ht: NaOH: NaOH, 0. 5mM HCl and heat treated, Na-50H-Ht: NaOH, 50 mM HCl and heat treated.</p