1. introduction
   1. stem cell
      1. definition
         1. A stem cell is a cell that has the ability to divide (self replicate) for indefinite periods—often throughout the life of the organism. Under the right conditions, or given the right signals, stem cells can give rise (differentiate) to the many different cell types that make up the organism. That is, stem cells have the potential to develop into mature cells that have characteristic shapes and specialized functions, such as heart cells, skin cells, or nerve cells
      2. important characteristics
         1. unspecialized cells capable of renewing themselves through cell division,
         2. under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions.
      3. role of stem cell in research
         1. Topic
      4. Topic
2. types of Stem Cells
   1. Embryonic stem cells (ES cells),
      1. def.
         1. The embryonic stem cell is defined by its origin—that is from one of the earliest stages of the development of the embryo, called the blastocyst. Specifically, embryonic stem cells are derived from the inner cell mass of the blastocyst at a stage before it would implant in the uterine wall. The embryonic stem cell can self-replicate and is pluripotent—it can give rise to cells derived from all three germ layers.
            1. Topic
      2. sources
         1. In Vitro Fertilization (IVF)
         2. Nuclear Transfer
         3. Stem Cells Found in Umbilical Cord Blood
   2. Adult stem cells,
      1. The adult stem cell is an undifferentiated (unspecialized) cell that is found in a differentiated (specialized) tissue; it can renew itself and become specialized to yield all of the specialized cell types of the tissue from which it originated. Adult stem cells are capable of self-renewal for the lifetime of the organism. Sources of adult stem cells have been found in the bone marrow, blood stream, cornea and retina of the eye, the dental pulp of the tooth, liver, skin, gastrointestinal tract, and pancreas. Unlike embryonic stem cells, at this point in time, there are no isolated adult stem cells that are capable of forming all cells of the body. That is, there is no evidence, at this time, of an adult stem cell that is pluripotent
         1. Topic
            1. nondental
            2. – Mesenchymal Stem Cells
            3. – Hematopoietic Stem cells
            4. – Neural Stem Cells
            5. – Muscle Derived Stem Cells
            6. – Pancreatic Stem Cells
            7. – Hepatic Stem Cells
            8. – Epithelial Stem Cells
            9. – Hematopoietic Stem cells
            10. – Mesenchymal Stem Cells
            11. – Neural Stem Cells
            12. – Muscle Derived Stem Cells
            13. – Pancreatic Stem Cells
            14. – Hepatic Stem Cells
            15. – Epithelial Stem Cells
            16. dental source
   3. Topic
3. application of stem cell
   1. General applications of stem cell (examples):
      1. * August 2, 2010 - A medical research team led by University of Miami doctors injected stem cells into the hearts of pigs that had been damaged by heart attacks. Within two months, the doctors said, the stem cells made the pigs’ hearts good as new.
      2. *Scientists have created part of the jaw joint (TMJ) in the lab using human adult stem cells via BBC NEWS | Health | Jaw bone created from stem cells.
   2. Application of stem cell in dentistry (examples) :
      1. *In 1995 McCulloch CA, 2008 Bartold PM, Scientists found that PL cell progenitors can generate multiple types of more differentiated, specialized cells including large numbers of fibroblastic cells and more limited numbers of osteogenic or cementogenic cells.
      2. *In 2003 Miura M isolated stem cells from exfoliated human deciduous tooth, were these stem cells capable of differentiating into a variety of cell types including neural cells, adipocytes, and odontoblasts.
      3. *Iohara K. 2004 found that Dentin can be regenerated by dental pulp stem cell therapy.
      4. *In 2005, Zang did a study on a rat. A rat dental pulp cells were isolated and their differentiation ability was evaluated. These cells showed the ability to differentiate into odontoblast-like cells and produced calcified nodules, which had components similar to dentin.
      5. *Ning L, 2010 Oct 11, did an experiment on mouse and his result indicate that stem cells have the potential to transdifferentiate into hematopoietic cells in vivo
4. key element of tooth engineering
   1. dental stem cell "progenitor cell"
      1. Because tooth development is dependent on epithelial and mesenchymal cell interac- tions, DSCs necessarily consist of two types:
         1. epithelial DSCs, which form ameloblasts, enamel, stellate reticu- lum, and stratum intermedium,
         2. and mesenchymal DSCs, which form the dental papilla, odontoblasts, predentin, dentin, cementum, PDL, and alveolar bone.
   2. inductive morphogenic signals (GF)
      1. def.
         1. signals used to promote dental tissue regeneration.
      2. types
         1. BMP
         2. FGF
         3. Hh
         4. Wnt
   3. scaffold
      1. def.
         1. a suitable three-dimensional carrier with tailored macroscopic properties, a well-tuned degradation profile, and specific biological cues are necessary to promote successful tissue growth (Abukawa et al., 2006; Ramseier et al., 2006)
      2. types
         1. polymers
            1. natural (collagen)
            2. dis adv.
            3. rapid absorption
            4. weak mechanical strength
            5. synthetic
            6. adv.
            7. can be fabricated into desirable sizes and shapes
            8. dis adv.
            9. poor biocompatibility due to release of acidic degradation products
            10. lose mechanical properties very early during degradation
         2. ceramic
            1. Tricalcium Phosphate
            2. adv
            3. biocompatibility,
            4. structural similarity to the inorganic component of bone.
            5. osteoconductivity,
            6. dis adv.
            7. material crystallinity, porosity, density, and host response
            8. Hydroxyapatite
      3. biodegradable scaffolds are desired that can initially facilitate proper epithelial and mesenchymal cell orientation, to guide the subsequent formation of highly mineralized tooth tissues
5. The Challenges of Stem Cell Therapy
   1. Identifying Stem Cells in Adult Tissues
   2. isolate the cell
   3. trigger the appropriate differentiate of stem cell
   4. Stem Cell Integration
      1. For example, if cardiac cells are implanted, they must be able to beat in sync with the patient's own heart cells. For a patient who suffers from a neural based disease, any neural cells must integrate into the complicated network of natural neural cells if they are to effectively function and replace damaged cells.
   5. Immunological Rejection
      1. Immunological rejection is a major barrier to successful stem cell transplants. When a patient's immune system views the transplanted cells as 'foreign' rather than 'self,' it wages an attack on the newly transplanted cells. Recipients of the transplant usually have to take strong immunosuppressive drugs to reduce the chances of rejection but these drugs then leave the patient vulnerable to infection by any other viruses or microbes in the environment.
   6. directing cell growth
      1. The challenge for scientists is to find a balance between directing cell growth into specialized tissues that can replace damaged ones, and also ensuring that cells don't excessively grow and become cancer cells.
6. Side Effects of Stem Cell Therapy
   1. Benign Tumour
   2. Weakened Immune System