Showing papers by "Iain R. Gibson published in 2005"

In vivo assessment of hydroxyapatite and silicate-substituted hydroxyapatite granules using an ovine defect model

Abstract: Phase pure hydroxyapatite (HA) and two silicate-substituted hydroxyapatites (0.8 and 1.5 wt% Si, or 2.6 and 4.9 wt% SiO4) were prepared by aqueous precipitation methods. The filter-cakes of HA and silicate-substituted hydroxyapatite (SiHA) compositions were processed into granules 1.0–2.0 mm in diameter and sintered at 1200°C for 2 h. The sintered granules underwent full structural characterisation, prior to assessment in an ovine defect model by implantation for a period of 6 and 12 weeks. The results indicate that HA and SiHA implants were well accepted by the host tissue, with no evidence of inflammation. New bone formation was observed directly on the surfaces and in the spaces between the granular implants. Quantitative histomorphometry as determined by the percentage of bone ingrowth and bone coverage for both SiHA implant compositions was significantly greater than that for phase pure HA. These findings indicate that the in vivo bioactivity of hydroxyapatite was significantly improved by the incorporation of silicate ions into the HA structure, making SiHA ceramics attractive alternatives to conventional HA materials for use as bone graft substitute ceramics.

In situ thermal and structural characterization of bioactive calcium phosphate glass ceramics containing TiO2 and MgO oxides: High temperature – XRD studies

Abstract: This study aims to develop glass ceramics in the calcium phosphate system that exhibit suitable properties to be used for biomedical applications. Calcium phosphate glasses with the incorporation of small additions of MgO and TiO 2 oxides were prepared in the pyro-and orthophosphate regions. The glass ceramics were prepared by a controlled powder sintering process through heat-treatment at different temperatures, as defined by results from differential thermal analysis (DTA). The composition of the crystalline phases precipitated in the glassy matrix as a result of heat treatments at different temperatures, ranging from 681 to 725 °C, was determined from X-ray diffraction data. The sequence of phase crystallization in the mother glass was also studied in situ using high temperature X-ray diffraction (HT-XRD) analysis. Results showed that the first phases that precipitated in the glass matrix were α- and β-Ca 2 P 2 O 7 at 620 °C. A small amount of CaTi 4 (PO 4 ) 6 appeared at 630 °C. At 650 °C the three phases α-Ca 2 P 2 O 7 , β-Ca 2 P 2 O 7 and CaTi 4 (PO 4 ) 6 were clearly presented with a small amount of TiP 2 O 7 and finally at 660 °C all four phases were observed. Glass ceramics were also characterized using Raman and X-ray photoelectron spectroscopy. This study demonstrates that, by altering the heat treatment cycle, it is possible to prepare glass ceramics in the calcium phosphate system that contains different bioactive and biocompatible phases.

In vivo assessment of hydroxyapatite and silicate-substituted hydroxyapatite granules using an ovine defect model

Abstract: Phase pure hydroxyapatite (HA) and two silicate-substituted hydroxyapatites (0.8 and 1.5 wt% Si, or 2.6 and 4.9 wt% SiO4) were prepared by aqueous precipitation methods. The filter-cakes of HA and silicate-substituted hydroxyapatite (SiHA) compositions were processed into granules 1.0–2.0 mm in diameter and sintered at 1200°C for 2 h. The sintered granules underwent full structural characterisation, prior to assessment in an ovine defect model by implantation for a period of 6 and 12 weeks. The results indicate that HA and SiHA implants were well accepted by the host tissue, with no evidence of inflammation. New bone formation was observed directly on the surfaces and in the spaces between the granular implants. Quantitative histomorphometry as determined by the percentage of bone ingrowth and bone coverage for both SiHA implant compositions was significantly greater than that for phase pure HA. These findings indicate that the in vivo bioactivity of hydroxyapatite was significantly improved by the incorporation of silicate ions into the HA structure, making SiHA ceramics attractive alternatives to conventional HA materials for use as bone graft substitute ceramics.

Synthetic calcium phosphate comprising silicon and trivalent cation

Abstract: Biomedical materials and, in particular, to substituted calcium phosphate (e.g. apatite and hydroxyapatite) materials for use as synthetic bone. A synthetic calcium phosphate comprising silicon and a trivalent cation having a formula Ca10−yMy(PO4)6−x(SiO4)x(OH)2−x+y where M is a trivalent cation, 0