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The Changing Face of Dental Biomaterials
(continued)
Tissue engineering
Looking further forward: tissue engineering
Constructing biological replacement parts outside of body and then implanting them
The triad of the tissue engineering
| Scaffold, Regeneration template - Gels - Foams - Fibers - Membranes |
||
| Cells - Cultured cells - Stem cells (adult, embryonic) - Autogenic / allogenic cells - Engineered cells |
Signal molecules - Families : TGF b FGF - Homeobox / Hedgehog / WNT |
|
| = Tissue prosthesis |
Some of the potentialities of tissue engineering
Strategies
 |
From the triad Cells - Signal Molecules - Scaffolds, both in vivo tissue regeneration and in vitro tissue engineering can be achieved. For the tissue regeneration, three different combinations (Signal Molecules, Signal Molecules+Cells, and Signal Molecules+Cells+Scaffold) can lead to tissue regeneration. The combination Signal Molecules+Cells leads to Cell therapy.
The tissue engineered tooth
Tissue Engineered Teeth Grown in Rat Jaw and Omentum
In a recent work, it has been demonstrated that a full tooth could be produced by using the techniques of tissue engineering. This is still more a curiosity than a practical development, but the authors had a clear aim : to create by tissue engineering techniques a viable biological substitute of a tooth.
| Tissue Engineered Teeth Grown in Rat Jaw and Omentum S.E. Dualibi, M.T. Dualibi, C.S. Young, J.P. Vacanti, P.C. Yelick, and J.D. Bartlett Universidade Federal De Sao Paulo-Escola Paulista, Brazil, Forsyth Institute, USA, Massachusetts General Hospital , USA Annual Meeting of the IADR 2002 San Diego, Abstract #1412 |
| and |
| Tissue Engineering of Complex Tooth Structures on Biodegradable Polymer Scaffolds CS Young, S Terada, JP Vacanti, M Honda, JD Bartlett et PC Yelick J Dent Res 81 (10):695-700, 2002 |
Strategy
 |
Dental germs from young 4 days rats are enzymatically dissociated and seeded on polyglycolic acid (PGA) scaffolds in the shape of a tooth
The elements so prepared are placed either in the omentum of the rat , or directly after extraction in a dental alveolus – and then left in place for 12 weeks.
The tissues produced by tissue engineering have then been compared to those of a natural tooth (control). The tissue implant obtained by tissue engineering contains clearly the following elements:
 |
d dentine
CS Young et al. |
This experiment indicates that when combining specialized cells (the dental germs from very young rats) with a scaffold placed in a biologic environment (the dental alveolus or the omentum), it is possible to produce a tooth substitute characterized by a proper shape and the presence of the constituting tissue of a natural tooth. This however has been achieved for the rat, and it is still to demonstrate that it can be applied to the man.
The main obstacles
Transfering the results of laboratory experiments to clinical applications for humans is facing three main obstacles:
| 1. | implantation of the tissue engineered parts - from the stage of fabrication to the stage of implantation, these parts have to be kept alive, and they have to find a functional place within the human body, with a proper supply of blood, oxygen and nutrients. In dentistry in particular, implanting a tissue engineered tooth would be a very difficult task, when contact with the bone, size, shape and position of the implanted tooth are so important to a proper and functional implantation |
| 2. | control of further development within the body - since most of the tissue engineered parts have been devloped using very potent signal molecules to induce the transformation the growth of the stem cells, a way has to be found to insure that these transformation and growth will not continue beyond control when implanted |
| 3. | aging - matching the aging of the implanted tissue engineered parts with that of the surrounding tissues and organs is a great obstacle too. |
In a chapter of a recent book, R.M. Nerem has listed the most critical issues for tissue engineering:
Critical Technical Issues in Bringing Tissue-Engineered Products to Market:
| - Adressing issues of cell sourcing - Developing interactive biomaterials - Engineering 3D constructs/healing reponses - Scaling up manufacturing processes - Preserving manufactured products - Controlling in vivo biological responses - Engineering immune acceptance - Assessing post-implantation viability |
From: Robert M. Nerem, in: « Tissue Engineering, Stem Cells and Gene Therapies », Kluwer, 2003
Tissue engineering offers many possibilities to solve problems beyond the present limits of dental biomaterials, but the move from a laboratory experiment to a feasable, reliable and economical solution is still extremely difficult, and the practical applications of tissue engineering in dentistry are still far away.
What are the consequences now ?
Conclusion| - Changes are more important in technologies than in biomaterials per se - Especially in fixed prosthodontics: the role of dental technician is changing - Biological alternatives: a vision for the next 30 years - The tools of tomorrow are still on the drawing boards - The dental profession will be changed by the emerging technologies - The academic education will have to change drastically to incorporate the most prominent innovations, such as the biological approaches |
Content
The faded (and fading) glories
The influence of public expectation
One step beyond: tissue regeneration