Development and characterization of 3CaO.P2O5-SiO2-MgO glass-ceramics with different crystallization degree

The CaO-P2O5-SiO2-MgO system presents several compounds used as biomaterials such as hydroxyapatite (HA), tricalcium phosphate (TCP) and TCP with magnesium substituting partial calcium (TCMP). The beta-TCMP phase with whitlockite structure has interesting biological features and mechanical properties, meeting the requirements of a bioactive material for bone restoration. In this work, the production of Mg-doped TCP, beta-TCMP, has been investigated by crystallization from a glass composed of 52.75 wt% 3CaO center dot P2O5, 30 wt% SiO2 and 17.25 wt% MgO (i.e., 31.7 mol% CaO, 10.6 mol% P2O5, 26.6 mol% MgO and 31.1 mol% SiO2) using heat treatments between 775. and 1100 degrees C for up to 8 h. The devitrification process of the glass has been accompanied by differential scanning calorimetry (DSC), high-resolution X-ray diffraction (HRXRD), relative density and bending strength measurements. The characterization by HRXRD and DSC revealed the occurrence of whitlockite soon after the bulk glass preparation, a transient non-cataloged silicate between 800 degrees C and 1100 degrees C, and the formation of diopside in samples treated at 1100 degrees C as crystalline phases. The overall crystalline fraction varied from 26% to 70% depending on the heat treatments. Furthermore, contraction of the a-axis lattice parameter and expansion of the c-axis lattice parameter of the whitlockite structure have been observed during the heat treatments, which were attributed to the beta-TCMP formation with the partial substitution of Ca2+ by Mg2+. Relative densities near 99% and 97% for the glass and glass-ceramics respectively indicated a discrete reduction as a function of the devitrification treatment. Bending strengths of 70 MPa and 120 MPa were determined for the glass and glass-ceramic material crystallized at 975 degrees C for 4 h, respectively

Extracting hydroxyapatite and its precursors from natural resources

Healing of segmental bone defects remain a difficult problem in orthopedic and trauma surgery. One reason for this difficulty is the limited availability of bone material to fill the defect and promote bone growth. Hydroxyapatite (HA) is a synthetic biomaterial, which is chemically similar to the mineral component of bones and hard tissues in mammals and, therefore, it can be used as a filler to replace damaged bone or as a coating on implants to promote bone in-growth into prosthetic implants when used in orthopedic, dental, and maxillofacial applications. HA is a stoichiometric material with a chemical composition of Ca10(PO4)6(OH)2, while a mineral component of bone is a non-stoichiometric HA with trace amounts of ions such as Na+, Zn2+, Mg2+, K+, Si2+, Ba2+, F-, CO3 2-, etc. This review looks at the progress being made to extract HA and its precursors containing trace amount of beneficial ions from biological resources like animal bones, eggshells, wood, algae, etc. Properties, such as particle size, morphology, stoichiometry, thermal stability, and the presence of trace ions are studied with respect to the starting material and recovery method used. This review also highlights the importance of extracting HA from natural resources and gives future directions to the researcher so that HA extracted from biological resources can be used clinically as a valuable biomaterial