CRANIOFACIAL BONE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 208

CHAPTER

10

CRANIOFACIAL BONE

Ben P. Hung 1 , Pinar Yilgor Huri 1 , Joshua P. Temple 1 , Amir Dorafshar 2
and Warren L. Grayson 1
1 Department of Biomedical Engineering, Translational Tissue Engineering Center,
Johns Hopkins University School of Medicine, Baltimore, MD, USA
2 Department of Plastic and Reconstructive Surgery, Johns Hopkins University School
of Medicine, Baltimore, MD, USA

10.1 INTRODUCTION
According to the Centers for Disease Control and Prevention (CDC), approximately one million
cases requiring bone transplantation occur annually in the United States, with around 20% of these
in the craniofacial region. This incurs an annual economic burden in excess of $3 billion
( Desai, 2007 ). Such cases may be caused by congenital disease, such as cleft lip ( Parker et al., 2010 ),
trauma such as combat injuries ( Breeze et al . , 2011 ; Tong and Beirne, 2013 ), or cancer resection.
Regardless of origin, they cause numerous quality-of-life afflictions, such as hindered psychosocial
well-being due to facial deformity or the inability to speak or eat due to mandibular or maxillary
defects.
Since the available supply of donor bone is far outstripped by this demand, there exists a press-
ing need for alternative sources of tissue. In tissue engineering (TE), the traditional paradigm is to
combine tissue-forming cells, appropriate bioactive factors, and a scaffold to construct tissue de novo
( Langer and Vacanti, 1993 ). Bioactive factors can include biochemical, mechanical, or electromagnetic
cues while the scaffold provides structural and geometrical guidance to the newly forming tissue at
the macro-, micro-, and nanoscales. The macroscale can be defined as geometry on the order of mil-
limeters and above, while microscale considerations are concerned with submillimeter length scales
down to the micrometer range. Below this submicrometer length scale is the nanoscale. Micro- and
nanoscale considerations, in particular, have to do with porosity : the amount of interconnected void
space available for cellular population and tissue infiltration; as well as nanotopography : the surface
features within the walls or struts of the scaffold that are smaller than the cells and can also instruct
and guide cellular behavior.
For bone in particular, the scaffold's structural support role is very crucial, as one of the primary
functions of bone is mechanical—it supports load, both from the organism's weight as well as from
forces exerted by attached muscles. In the craniofacial region, the geometrical role of the scaffold