Magnesium‐substituted hydroxyapatite ceramics

Abstract

The effect of the addition of magnesium (up to 10 wt%, expressed as MgO) on the phase composition, the microstructure and the mechanical properties of hydroxyapatite-based ceramics (HA) was studied by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and mechanical testing. Doping with magnesium did not change the crystal lattice of HA but, due to an isomorphous substitution of Mg 2+ for Ca 2+ , it caused a decrease in the average grain size, an increase of microporosity, a removal of the texture, and the formation of a weak intergranular boundary. The transcrystallite fracture pattern of pure HAwas changed to a predominantly intercrystallite one. This resulted in a decrease in density (down to 2.93 g cm -3), in microhardness (down to 400 MPa), in compressive strength (down to 190 MPa) and in improved plastic properties of the material (increasing the fracture toughness K 1C up to 2.7 MPa m 1/2 , close to that of the bone). It is interesting that the K 1C increase could be only observed for a small concentration of additives (up to 1 wt%), i.e. close to the Mg concentration in natural bone mineral.

Mg-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sintering behaviour

“…It can be observed that in the case of 0.25Mg-HAp and 0.5Mg-HAp nanopowders, the particle size decreased with Mg content, in good agreement with Zyman et al 29 As reported in Table 2, both as-dried samples showed a (Ca + Mg)/P ratio close to the stoichiometric value of HAp (i.e. 1.667) and presented a low volume fraction of ␤-TCP (Table 3a).…”

“…Moreover, as the Mg content increased, a slight shift of the OH − peak at 3572 cm −1 and a considerable broadening of the 700-1700 cm −1 phosphate bands were observed. 29 In detail, in the case of 1.0Mg-HAp sample, extra peaks at 942, 948, 962, 972, 986 1 , 1044, 1090, 1120 cm −1 were detected. These bands can be ascribed to the PO 4 3− vibration modes characteristic of tricalcium phosphate, in good agreement with Pena and Vallet-Regi 30 (Fig.…”

Cationic and Anionic Substitutions in Hydroxyapatite

“…Concerning the mechanical properties, Mg incorporation significantly decrements compressive strength and microhardness up to a Mg content of 1.8 wt% [67] and causes an increment of the fracture toughness with Mg amount up to 0.6 wt%, content very close to the magnesium concentration in the natural bone mineral component. These experimental evidences were ascribed to the decremented average grain size, the increased microporosity, and the formation of a weak intergranular boundary [61,67].…”

“…These experimental evidences were ascribed to the decremented average grain size, the increased microporosity, and the formation of a weak intergranular boundary [61,67].…”

“…It has been demonstrated that magnesium deficiency is directly correlated with osteoporosis, negatively influencing all skeletal metabolism stages, with consequent inhibition of bone growth, decreased osteoblastic and osteoclastic activities, osteopenia, and bone fragility [43,44]. , by a combination of melting and extrusion routes with the use of a melted 99.9 % pure Mg ingot [65], by surfactant-assisted microwave synthesis [66], by wet mixing [67], and by mechanochemical-hydrothermal route [42].…”