|ORTHODONTICS AND BEYOND: INVITED ARTICLE
|Year : 2015 | Volume
| Issue : 1 | Page : 53-54
Stem cells in Dentistry - The here and now!
Prof. and HOD, Department of Periodontics, Sri Ramachandra University, SRMC, Chennai, Tamil Nadu, India
|Date of Submission||25-May-2015|
|Date of Acceptance||26-May-2015|
|Date of Web Publication||12-Jun-2015|
Department of Periodontics, Sri Ramachandra University, Porur, Chennai - 600 116, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Suresh R. Stem cells in Dentistry - The here and now!. J Indian Orthod Soc 2015;49:53-4
For years now wishful thinking for researchers and a dream for clinicians has been to "grow" a tooth. From a researcher's point of view, a full tooth can replace many lost ones but for a clinician, even growth of its constituent parts will help by preventing loss of the tooth itself. The day is not too far for both. However, the clinicians stand a better chance of achieving this in the near future. It is the most rewarding experience if one realizes what goes into developing the constituent parts of a tooth.
This revolutionary science is more than a century old. In 1878,  the first attempt was made to fertilize mammalian eggs outside the body. The first in vitro human egg fertilization was performed in 1968.  In 1970, for the first time embryonic stem cells were injected into the mouse blastocyst to make chimeric mice (mice with genetically different cells).  In 2000, researchers isolated embryonic stem cells and injected them into animals to produce chimeric mice.
All cells cannot induce chimerism. Only cells that are pluripotent can achieve that. The potency of stem cells depends on how many types of cells can differentiate from the parent cells, and this capacity is called plasticity. A fertilized egg and the initial few cells are the most potent and are called totipotent meaning those which can give rise to the entire functional organism. Following this are pluripotent cells that find a niche to stay and give rise to multipotent stem cells which are less potent than pluripotent cells with limited lineages of cell development. In adults, there are cells that stay in differentiated tissues to give rise to progenitors as a routine mechanism for remodeling. These are referred to as adult mesenchymal stem cells. A breakthrough in dental stem cell research was achieved in the year 2006 when Takahashi and Yamanaka made embryonic stem cells from adult fibroblast cultures called "induced pluripotent stem cells." 
Initially, researchers considered blood and the bone marrow to be the best sources to obtain stem cells. However, Gronthos et al. demonstrated the dental pulp stem cells as the first dental stem cells and today by their property of plasticity they can be regarded the gold standard amongst dental stem cells.  In due course after the discovery of the Gronthos team the list of dental sources for stem cells became long ranging from stem cells from human exfoliated deciduous teeth, periodontal, gingival, dental follicle, apical papilla, oral mucosal to induced pluripotential stem cells from gingival fibroblasts. Today it is well documented that these dental stem cells are of neural crest origin, pluripotent in property and the future of regenerative medicine.
There are two ways in which dental stem cells play a major role in regenerative medicine. These cells have an immunosuppressive property which has been exploited to treat gastric ulcers and oral ulcers. On the other hand, they have been differentiated into bone, adipose tissue, cartilage and neurons for tissue engineering. Due to the discovery of stem cells and recombinant growth factors tissue engineering has transformed from a myth to reality.
Extensive research into the regeneration of enamel, pulp, dentin and periodontal structures is in progress. Definitive regeneration of lost bone is a reality and is highly achievable in the clinical setting today. As for the pulpo-dentine, complex experiments into the regeneration of both the tissues are yielding encouraging results. In maxillofacial critical defects, rapid prototyping is of great use in designing scaffolds that outline the part of mandible or maxilla to be regenerated and facilitates to hold the cells and growth factors as a carrier.
Periodontal regeneration has advanced by leaps and bounds. The availability of stem cells and growth factors prompted researchers to apply it in many ways.  From coating of scaffolds with growth factors and seeding stem cells on scaffolds, the latest development is the cell sheet technology where stem cells are cultured and made into sheets that can be applied to desired surfaces to be regenerated.
Engler, et al. a pioneer in mechanobiology, demonstrated how mechanical properties of scaffolds can differentiate stem cells.  Computational studies like finite element analysis have been used for designing scaffolds with desired mechanical properties. Interestingly finite element analysis has also been utilized to assess what lineage stem cells will finally take to. Early orthodontic tooth movement studies have helped in applying mechanobiology concepts to periodontal regeneration. 
The application of stem cells in orthodontic treatment is in a primitive and nascent stage. The initial use will be in periodontal or maxillofacial areas, the two tissues which are fundamentally needed for orthodontic treatment to be fruitful. More specifically, in orthodontic treatment stem cells will make a difference in hastening matured (functional) tissue regeneration. Stem cells from the apical papilla may be used to prevent or correct root resorption. These in combination with other stem cells like periodontal ligament stem cells have been experimented in pulpal and dentine repair. This modality is referred to as bio root engineering. The use of stem cells in mid palatal suture areas after maxillary expansion to accelerate new bone formation has also advanced to the stage of preclinical experimental studies.
Orthodontic treatment is largely dependent on the properties of the periodontal ligament with its fiber orientation at different levels and angulations. It is ideal to regain this architecture after regeneration. Recent scaffold designs are aimed not only at bone/cementum regeneration, but also at regenerating the periodontal ligament fibers with their orientation similar to that of natural teeth. 
Many regenerative methods and materials have been used in orthodontic treatment especially in periodontally accelerated osteogenic orthodontics. Going by the functional matrix theory, the whole housing around the root is essential to prevent relapse following orthodontic treatment. Regenerating quantity and quality hard and soft tissues in a shorter span of time are possible only with stem cells and other regenerative materials.
Last but not the least, Praveen Arany et al. have recently performed an interesting experiment by administering LASER into a drilled tooth based on the stimulating properties of these rays. They found that LASER rays reached up to the stem cells underneath, and in 12 weeks new dentine formation was observed.
In conclusion, the role of regenerative medicine in orthodontics cannot be underestimated. As stem cell availability becomes plentiful, and as scaffold designs get better, regenerative medicine in the form of tissue engineering will gain roots into the orthodontic specialty and orthodontic treatment modalities will become highly predictable.
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