CRANIOFACIAL AND DENTAL TISSUE - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 192

9.3 CRANIOFACIAL AND DENTAL REGENERATIVE MEDICINE RESEARCH
Despite the great need, there is very little penetration of tissue engineering, especially additive manu-
facturing or cell printing for tissue engineering, in standard-of-care craniofacial surgical and/or den-
tal therapeutic procedures that repair critical size defects ( Schmitz and Hollinger, 1986 ). However,
the significant use in these specialties of bone and tooth substitute materials, especially in regard to the
additive manufacture of patient-specific medical implants, may eventually forge a link between tissue
engineering and craniofacial and dental care.
9.3.1 NOVEL MATERIALS
Implants and surgical reconstruction hardware for the craniofacial and dental regions have typically
used the same materials as elsewhere in the body. However, there are many advanced materials that are
used fairly exclusively in the craniofacial region. Resorbable Lactosorb ® (Lorenz [Biomet], Jacksonville,
FL), which is 82% poly(-L lactic acid) and 18% poly(glycolic acid) is one such example ( Biomet micro-
fixation, 2010 ). These plates and screws resorb by hydrolysis within a year, allowing uninhibited growth
of the bones and obviating the need for a secondary procedure to remove the hardware. These plates have
particular application in softer bones, such as in the orbit and in infants. Solid-state hyaluronic acid in the
form of a thread is another advanced material used in the craniofacial region. This promising new product
allows for more controlled wrinkle effacement and soft tissue augmentation ( Franklin, 2014 ). Nitinol-
shape memory metals are used in orthodontic wire; these wires are superelastic at body temperature.
As mentioned previously, titanium dental implant bone screws and abutments are very successful.
However, there is a great deal of innovation with other alloys, zirconia, and coatings designed to improve
osseointegration. Single crown or fixed prosthesis implant dental systems are currently more expensive
than nonfixed systems (e.g., traditional dentures), but they also provide for better mechanical function,
stimulation, and maintenance of oral cavity muscles and skeletal structures. However, the most exciting
and cutting-edge application of such advanced biomaterials is in their use in the additive manufacture
(3D printing) of patient-specific implants in teeth, craniofacial bone, and the temporomandibular joint.
9.3.2 TEETH
The Sirona CEREC1 (Chairside Economical Restorations of Esthetic Ceramics), the first system to
combine digital scanning of the teeth, and computer-aided design (CAD) of prosthetic crowns, appeared
in 1985. Most of these crown restorations are currently prepared in the prosthodontist's office or by a
nearby service with computerized milling devices. These systems are sufficiently accurate ( Figure 9.4 ),
therefore there seems to be no benefit in terms of quality or price at this time in moving to more
advanced fabrication strategies ( Schaefer et al., 2013 ).
Ng et al., (2014) noted that it is only recently that restorations prepared in this way have be-
come more economical and perform better than traditional manual methods. Given the success of
these post-and-crown systems, the challenge for oral health has reverted back to the issue of sufficient
bone bulk to support dental posts. This is especially challenging in edentulous individuals ( Cho and
Raigrodski, 2014 ). Dental implants and single crown or fixed prostheses may require autologous and/
or alloplastic bone graft materials. This depends on the size of the alveolar cavity left following dental
extraction. It is unclear at this time whether these expensive fixed prostheses will become standard of
care under the United States' Affordable Care Act in nontraumatic situations ( O'Brien, 2014 ).