Biomedical Engineering Reference
In-Depth Information
2006). The microstructure of the used -TCP has important influence on the osteogenic
effects (Okuda et al., 2007). This has recently been confirmed by Fellah and colleagues
(Fellah et al., 2008). They show that the Hap/TCP with different micropores was evaluated
in a goat critical-defect model.
Several research studies dealt with the question where and how to perform the osteotomy
and which fixation material is most beneficial (Brouwer et al., 2006; Agneskirchner et al.,
2006). Aryee et al. demonstrate histologically and radiologically that the complete
rebuilding of lamelliform bone in patients without synthetic augmentation, whilst bony in
growth into the Hap/TCP wedge of augmented osteotomies just slowly progressed (Aryee
et al., 2008). In contrast to diminished osteotomies, there was no advantage in using
Hap/TCP wedges or the combination of Hap/TCP wedges and platelet rich plasma (PRP)
as supporting material after 12 months. In cases where augmentation is performed, either
autologous spongious iliac bone graft or an Hap/TCP wedge of appropriate size was
inserted into the osteotomy opening and pushed laterally until it is firmly aligned to the
tibial bone. The Hap/TCP wedge utilised by us consists of 60% micro-macroporous
biphasic Hap and 40% -TCP. The average total porosity is 65-75%, whilst two different
sizes of porosity are found within this material. The microporous part consists of pores with
a diameter less than 10µm. The macroporous part consists of pores with a diameter between
300µm and 600µm (same as autograft macropores).
As a result of limited autologous bone availability and to minimise the problem of donor-
site morbidity, many efforts have been made to find adequate supporting material for
augmentation after osteotomy (Bauer et al., 2000; De Long et al, 2007). In this context, we
chose biomaterials on base of calcium phosphates as solution for the biomedical
applications. Thus, β-TCP or Hap-TCP combination has been clinically used to repair bone
defects for many years (Elliott, 1994). Whereas, β-TCP or Hap-TCP have poor mechanical
properties (Elliott, 1994; Wang et al., 2004). The usage at high load bearing conditions was
restricted due to its brittleness, poor fatigue resistance and strength. Hence, there was a
need for improving the mechanical properties of these materials by suitable biomaterials for
clinical applications. We offer the study of the mixtures of tricalcium phosphate (β-TCP) and
synthetic Fap in order to obtain a bioceramic with better mechanical properties than Hap-
TCP combination or β-TCP as separately used. In fact, Fap is an attractive material due to its
similarity in structure and bone composition in addition to the benefit of fluorine release
(Elliott, 1994; Ben Ayed et al., 2001a). In Vitro studies we have shown that Fap is
biocompatible (Elliott, 1994). It also has better stability and provides fluorine release at a
controlled rate to ensure the formation of a mechanically and functionally strong bone
(Elliott, 1994; Ben Ayed et al., 2006b).
Most studies have been devoted to the knowledge of the mechanical properties and
biomedical applications of TCP-Hap (Elliott, 1994; Landi et al., 2000; Gutierres et al., 2007).
On the contrary little work has been devoted to the sintering, mechanical properties and
clinical applications of TCP-Fap (Ben Ayed et al., 2007). So, the aim of this study is to
prepare a biphasic calcium phosphates composites (tricalcium phosphate and fluorapatite)
at various temperatures (between 1100°C and 1450°C) with different percentages of fluorine
(0.5 wt %; 0.75 wt %; 1 wt %; 1.25 wt % and 1.5 wt % respectively, to the mass Fap
percentage: 13.26 wt %; 19.9 wt %; 26.52 wt %; 33.16 wt % and 40 wt %). It also aims to
characterize the resulting composites with density, mechanical resistance, infrared
spectroscopy, X-ray diffraction, nuclear magnetic resonance (
31
P) and scanning electron
microscopy measurements.
