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separated by gradual traction. The consolidation period
represents the time needed for a complete bridging of
the distraction gap by bone and a further maturation of
this bone. In general, the bone consolidation phase takes
approximately 6–12 weeks in the craniomaxillofacial
region and 3–6 months in long bones. [53]
Various methods have been tested to promote bone
formation in the distraction gap, e.g. electrical
and mechanical stimulation, [54] transplantation of
osteoblast-like cells, [55] administration of growth
factors such as bone morphogenetic proteins, or
fibroblast growth factor 2. Another procedure to
[56]
accelerate bone regeneration involves the application
of osteogenic proteins in the distraction gap using
nanotechnology-fabricated drug-release systems. [57]
Figure 5: A 15-year-old boy presented with osteosarcoma of the distal
tibia. Radiographs demonstrate initial resection and the placing of the Much research effort has been committed to the
bone transport device (left), midpoint of transport (middle), and after investigation of ordered mesoporous silica materials
bony consolidation (right)
in the biomedical field for two main reasons: their
ability to regenerate bone tissue and their drug
[58]
no treatment for the healing of critical calvarial defects delivery possibilities. When these silica-based ordered
[59]
in a rat model. Adding BMP-2 to these scaffolds further mesoporous materials are exposed to the physiological
improved bone regeneration, in both a rat and a clinical environment, a series of chemical reactions take place
model (data not shown).
in the material–living tissue interface, which lead to
incorporation of the material into the living tissue.
OSTEODISTRACTION AND
NANOTECHNOLOGY DRUG‑ Available pore volume and surface play a key role in
the protein-loading capacity of silica-based ordered
RELEASE SYSTEMS mesoporous materials. If large biomolecules, such as
certain proteins, are targeted to be adsorbed in ordered
One area of focus in nanotechnology is the delivery mesoporous materials, these matrices should present
of osteogenic factors in an attempt to modulate the several characteristics: (1) a large size pore size to allow
formation of bone. Research has focused on the use of diffusion; (2) a large surface area to allow a large retention
biodegradable materials as scaffolds for cellular ingrowth, percentage; (3) and a high pore volume to offer available
cell transplantation, or the delivery of therapeutic space into the mesopores to be filled by the protein.
molecules as methods for regenerating osseous tissue.
Several natural and synthetic polymers have been explored
Since Urist et al. demonstrated that glycoproteins for use as delivery vehicles for bone-inductive molecules.
[52]
extracted from demineralized rabbit could induce bone The poly (α-hydroxy acid) family of polymers, including PLA,
formation in ectopic sites in tibia matrix from rabbits poly (lactic-co-glycolic acid) (PLGA), and their copolymers,
and mice, tremendous advances have been made in the have been the focus of much of this research as they are
development of recombinant growth factors, proteins, biocompatible, undergo controllable hydrolytic degradation
and peptides for the regeneration of bone tissue. These into natural metabolites, and can be processed into many
factors have been shown to induce bone formation within forms. In addition, microparticles of PLA and PLGA have
[60]
a defect without the use of a carrier, but their relatively been used to deliver many factors, including transforming
short half-lives necessitate the use of significant amounts growth factor 1 and BMP-2, into osseous defects. Finally,
[61]
of protein. porous PLGA scaffolds have also been developed to provide
support for cellular migration. Some of this work focused
To increase the in vivo efficacy as well as reduce the on the adsorption of therapeutic agents onto prefabricated
quantities needed, the development of carriers capable scaffolds, but control of the factor’s release kinetics was
of controlled, sustained delivery of proteins and peptides found to be limited with this technique.
is desirable. In order to minimize surgical intervention
for the implantation of controlled-release scaffolds,
the development of materials that can be injected and FUTURE CHALLENGES
cross-linked in situ would be desirable.
Bone growth and remodeling involves a plethora of growth
DO is characterized by the formation of new bone factors, recruitment of mesenchymal stem cells, and the
between two osteotomized bone segments, which are action of three different mature cell types (osteoblasts,

10 Plast Aesthet Res || Vol 1 || Issue 1 || Jun 2014