Organ Regeneration Based on Developmental Biology

85

partitioned periodontal tissue structure (Fig. 5.4b). In the case of edentulous jaw or
following segmental mandibulotomy, it would be possible to achieve the multiple
teeth restoration by using this regenerative transplantation method (Oshima et  al.
2011 ). These technologies have the potential to be adapted for functional tooth
regeneration and also represent a substantial advance in bioengineered organ
replacement regenerative therapy.

5.5 Functional Whole-Tooth Replacement Using

the Bioengineered Tooth

Teeth have important oral functions such as mastication, pronunciation and facial
aesthetics, which have a critical influence on general health and quality of life
(Dawson 2006 ). These tooth-related functions are achieved along with masticatory
muscles and temporomandibular joint under the control of the central nervous sys-
tem (Dawson 2006 ). To desire a successful tooth replacement therapy, a bioengi-
neered tooth must be capable of being grafted into the tooth-loss region under adult
oral environment and achieving full functionality, including sufficient occlusal per-
formance, biological cooperation with the periodontal tissues and afferent respon-
siveness to noxious stimuli in the maxillofacial region.

5.5.1 Successful Transplantation of a Bioengineered Tooth

Germ or a Bioengineered Mature Tooth Unit

for Whole- Tooth Replacement Therapy

The critical issue regarding whole-tooth regenerative therapy via the transplantation
of a bioengineered tooth germ is whether the germ can erupt into the oral cavity and
occlude correctly with the opposing tooth under the adult oral environment. Natural
tooth eruption is autonomously progressed by a regulatory mechanism that involves
the tooth germ-cell components and the surrounding alveolar/jawbone (Wise et al.
2002 ; Wise and King 2008 ). Dental follicle cells contribute to overlying bone
resorption by enzymatic degeneration during growth and the axial movement of the
teeth during the process of tooth eruption (Wise and King 2008 ). It has been reported
that a transplanted natural tooth germ can erupt in a murine toothless diastema
region (Nakao et al. 2007 ; Ohazama et al. 2004 ). We have recently reported that a
bioengineered tooth germ can develop with the correct tooth structure and com-
pletely erupt in an oral cavity at 49 days after transplantation (Nakao et al. 2007 ;
Ikeda et al. 2009 ) (Fig. 5.5a). Additionally, the erupted bioengineered tooth not only
reached the occlusal plane but also performed occlusal function with the opposing
natural tooth (Ikeda et al. 2009 ) (Fig. 5.5a).

5 Functional Tooth Regeneration