Stem cells are unique type of cells that have specialised capacity for self-renewal and potency. They can give rise to one or many different cell types. They are found in many multi cellular organisms and are characterised by the ability to renew through mitotic cell division while maintaining the undifferentiated state. Stem cell therapy involves manipulation of the pluripotent cells in vitro and applying it for various therapeutic purposes. The possible applications of stem cells are replacement and repair of tissues and organs.
However, recent studies have revealed that replacement of dentofacial structure is rather challenging as it involves functions such as facial expression, articulation, chewing and swallowing. These are delicate functions involving a complex anatomical structure and co-ordination formed from both soft and hard tissues. Therefore stem cells, biomimetic materials, and various growth factors are essential to form these three-dimensional structures. Since the last few decades, scientists have been researching the possible applications of stem cells for restoring and regeneration of dental and dentofacial structures.
STEM CELL TYPES:
Stem cells can be broadly divided into 3 types:
- Embryonic stem cell
- Adult stem cell
- Hematopoietic stem cell
- Mesenchymal stem cell
- Induced pluripotent stem cell
Embryonic stem cell
Embryonic stem cells are capable of multi-potential differentiation but clinical feasibility is limited due to ethical issues, as the inner cell mass (the part that would form foetus) of the embryo is used to form embryonic stem cell.
Adult stem cell
Adult stem cells are multi-potent stem cells. They have been harvested from different kind of tissues like bone marrow, umbilical cord, amniotic fluid, brain tissue, liver, pancreas, cornea, dental pulp, and adipose tissue. Adult stem cells are comparatively easier to isolate and do not have any ethical issues. Immune rejection and teratoma formation is also rare with adult stem cells. Adult stem cells are commonly used in current day practice.
Induced pluripotent stem cell
Induced pluripotent stem cells(IPS) is an evolving concept in which 3–4 genes found in the stem cells are transfected into the donor cells using appropriate vectors. The stem cells thus derived by culturing will have properties almost like embryonic stem cells. This path breaking discovery may have a major role in future stem cell therapy.
DENTAL PULP STEM CELLS:
In 2003 Dr. Songtao Shi, a Pedodontist discovered dental pulp stem cells by utilizing the primary teeth of his daughter. Ever since then much research work has been conducted on dental pulp stem cells. It has been established that dental pulp stem cells is rich in different types of stem cells, like, adipocytes, chondrocytes, osteoblasts and mesenchymal stem cells. These mesenchymal stem cells are one of the most prospective stem cells which have wide therapeutic functions. Dental pulp stem cells can be found both in adults and children.
Stem cells can be separated from three groups of healthy unexposed teeth, they are:
(a) Deciduous Teeth
(b) Wisdom Teeth
(c) Permanent teeth: Eg. Premolars/Bicuspids extraction for orthodontic treatment.
DENTAL STEM CELL ADVANTAGES:
The advantages of stem cells from oral and maxillofacial region is as follows,
- They have high plasticity.
- It can be cryopreserved for longer period (Ideal for stem cell banking).
- It showed good interaction with scaffold and growth factors.
- Stem cells transplantations can cause pathogen transmission and also need immunosuppression, so autologous stem cell source is the best option. Dental pulp stem cells will be better fitting tool due to easy surgical access, the very low morbidity of the anatomical site after the collection of the pulp.
CLINICAL APPLICATION OF STEM CELL THERAPY IN THE ORO- MAXILLOFACIAL REGION
- Regeneration of pulp-denting complex:
- Dental pulp tissue has the regenerative potential to form dentin in response to any injury. Regeneration of the pulp inside the damaged tooth can be the basic clinical application of stem cell therapy in dentistry. For example, root canal treatment in a young permanent molar will stop the tooth’s continuous maturation process there by leaving thin egg shell like weak tooth that is susceptible to fracture. Regeneration of pulp with stem cell therapy will be a better option.
- Stem cells in periodontal tissue regeneration:
- Stem cells will be a promising tool for regenerating the periodontal structures such as periodontal ligament and other supporting elements. Bone Marrow Stem Cells (BMSC) have the ability to produce alveolar bone, periodontal ligament, and in vivo cementum after implantation into the periodontal defects. Thus, it was proved BMSCs provides an alternative source for the treatment for periodontal diseases.
- Regeneration of cranial facial defects
- Stem cells can be useful in the regeneration of bone and to correct large cranio-facial defects due to cyst enucleation, tumor resection, and trauma. The closure of a bone defect is commonly carried out with the transfer of tissue, which have disadvantages like, not able to restore the unique function of the lost part, donor site morbidity, accompanied by scarring, infection and loss of function. Stem cells isolated from dental pulp have a potential to differentiate into osteoblasts and are a good source for bone formation. Stem cells from oral and maxillofacial region can be combined with bone marrow stem cells to correct larger defects. This new procedure has added advantage of permitting the transplantation of more cells and better integrity compared with cell suspensions or gels.
- Future tissues:
- Future tissues like tissue engineered bone grafts, engineered joints and cranial sutures can be developed with stem cell therapy. The ability to design anatomically viable and functional bone would have great potential for oro-maxillofacial reconstructions of congenital defects, cancer resections, and trauma.
- Tooth regeneration:
- The regeneration of adult teeth will be possible in future with the newer advancement in stem cell therapy and tissue engineering. Regenerative procedures would be better fitting and alternative tool in place of dental implants.
There is still much to learn about the nature, potentiality and behavior of dental stem/progenitor cells. However, the opportunities for their exploitation in dental tissue regeneration are immense and will lead to significant benefits for the management of the effects of dental disease. Regenerative dentistry will have to go in pace with regenerative medicine. On the other hand, stem cells should be differentiated to the appropriate cell types before they can be used clinically, otherwise it might lead to deleterious effects.
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Article written by,
Dr. Shilpa Hiremath