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Title: Bone formation on calcium phosphate bone substitute materials
Author: Samizadeh, S.
ISNI:       0000 0004 2727 5936
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2010
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A large number of bone substitute materials are available; for which some authors claim osteoconductivity and some osteoinductivity. In order to rank these materials an in vivo analysis was carried out. These materials were chosen based on their availability and claimed mode of action. Silicon substituted Hydroxyapatite (SiHA), Hydroxyapatite (HA), Resorbable Calcium Phosphate Silicon, Skelite [siliconstabilized tricalcium phosphate-based bone substitute], Pro Osteon 500R [coralline HA], BiIonic [Yttrium stabilized SiHA] and two non-calcium phosphate, Dimeneralised Bone Matrix (DBM) based biomaterials: Accell Connexus DBM putty and Grafton crunch DBM were implanted in sheep femoral condyle defects for 6 weeks. Implanted calcium phosphate (CaP) based biomaterials demonstrated superior bone formation in comparison with the DBM samples. Silicon within CaPs increased the rate of bone formation in vivo. Silicon substituted HA showed increased proliferation rate (P<0.05) of human marrow stromal cells compared to pure HA in vitro. Expression of osteoblastic marker genes RUNX2, Osterix and Osteopontin within the hMSCs indicated the differentiation of preosteoblasts into osteoblasts, and osteogenic development on both HA and SiHA. Expression of osteocalcin and bone sialoprotein genes on HA and SiHA samples indicated the activation of mineralisation process. Differentiation of hMSCs into osteoblasts in vitro suggested a role in promotion of osteoinduction by both HA and SiHA. Implantation of porous SiHA and HA in paraspinous muscle of sheep, exhibited new bone formation through osteoinduction. SiHA indicated significantly higher new bone formation (P<0.01) compared to HA. SiHA and HA biomaterials with higher strut porosity (30%) indicated greater bone formation (P<0.05). In conclusion, CaP based biomaterials demonstrate superior bone formation in comparison with DBM biomaterials. Silicon substitution within HA enhances the cellular activity of hMSCs. Osteoinduction was greatest on SiHA with higher strut porosity. This result is believed to be due to a combination of the effect of interconnected porosity and chemical composition of the bone substitute.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available