Biomedical Engineering Reference
In-Depth Information
radiographically from zero to fi ve years, with biopsies taken at different time
periods from six months to fi ve years [116]. The radiographs revealed newly-
formed bone with higher density and residual BCP granules. After six months, a
lesser amount of BCP granules with 20HA/80TCP were observed compared to
50HA/40TCP. In addition, during drilling, clinicians reported higher bone den-
sity without interference from residual granules. Organised and well-mineralised
bone ingrowth was observed using micro CT and light microscopy. In all cases,
the radiopacity of the implantation sites decreased with time indicating that re-
sorption and bone ingrowth proceeded at the expense of the BCP granules. Ob-
servation after one and fi ve years showed that alveolar ridge height had been
maintained, compared to the control (no BCP) which showed a decrease in al-
veolar ridge height of two to fi ve mm. Five years after implantation, the resorp-
tion of the BCP was 78% for the 60/40 and 87% for the 20/80, and bone ingrowth
38% and 32%, respectively. Resorption and bone ingrowth were not signifi cantly
different for the BCP of different HA/TCP ratios.
4.5.1.2 Sinus Lift Augmentation.
The problems involved in delivering
MBCP granules into tooth sockets has discouraged many dental surgeons. A
recently developed product composed of MBCP granules in a polymer carrier
provides a ready-to-use injectable bone substitute (MBCP Gel™ ) [95] . The os-
teoconductive potential of this innovative biomaterial has already been demon-
strated for clinical applications in an animal model with the quantifi cation of each
component, BCP, bone and soft tissue [17]. Macroporous BCP in a polymer car-
rier has been shown to be effective in fi lling dental sockets after tooth extraction
because it maintained the alveolar bone crest, supported bone healing and was
gradually substituted by bone tissue.
In
vivo
resorption, just like
in
vitro
dissolution, depends on chemical compo-
sition and particle size [117]. MBCP Gel™ with 40 to 80
m BCP granules was
used for bone regeneration around dental implants placed in fresh extraction
sockets in a dog model [101]. Three months after implantation, the BCP granules
were no longer visible using SEM. In the same animal model and after the same
implantation time, most of the BCP granules (200 to 500
μ
m granules) were still
present. In the case of nanoparticles (BCP particle size smaller than ten
μ
m),
complete and fast resorption of the BCP granules was observed, but so was sig-
nifi cant infl ammation [51]. The particle size of the BCP (or any resorbable bioma-
terials) should thus be adapted to the clinical situation. For pre-prosthetic surgery
large granule size compatible with injection should be used out of preference and
for pre-implantation surgery, small granule size compatible with acceptable levels
of infl ammation is recommended.
μ
4.5.2 Applications in Orthopedics
BCP has been used in orthopedic applications for the last 20 years. Its effi cacy
has been demonstrated in numerous preclinical and clinical studies [26-31,118-
120]. Below are brief descriptions of selected clinical situations using specifi c
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