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mechanisms that can maintain the functional integrity of tissues
Which tissues undergo continual turnover also termed _________________.
blood and epithelia, known as maintenance or homeostatic regeneration
Blood and epithelia regenerate on a larger scale when damaged, a process called ___________
The main reason for pulp needing pulpotomy or tooth extraction is
pulp having weak regenerative capacity
In what year and who is credited for origination of regenerative dental procedures
1952 B.W. Hermann, applied CaOH to vital pulp amputation
Who developed Emdogain?
Three objectives of regenerative endo:
- 1. regenerate pulp-like tissue (pulpodentin complex)
- 2. regenerate damaged coronal dentin
- 3. regenerate resorbed root, cervical, or apical dentin
- AAE defined these in 2007
Who first defined tissue engineering?
Langer and Vacanti
______ _____________ is the employment of _________ therapeutic strategies aimed at the ____________, ______, _________, and/or _____________ of tissue function
- Tissue engineering
__________ medicine represents applications that ______ or ______ structural and _________ tissues, including bone, _________, and blood vessels
Define progenitor cell
immature or undifferentiated cells found in postnatal animals
Define stem cell
cell that has ability to continuously divide AND produce progeny cells that develop into other cells and tissues
Where do all tissue originate from?
Where are stem cells populations established?
Niches, they save stem cells from depletion
Stem cell types, two:
Different potentials of stem cells to differentiate is termed:
Which stem cell group has greater plasticity?
embryonic over postnatal
Define totipotent (1st Stage):
early embryo cells (1-3 days) can develop into all of the tissues in a new individual
Define pluripotent (2nd Stage):
cells from blastocyst (5-14 days) can form more than 200 tissue types
Define multipotent (3rd Stage):
- 1. cells from ecto, endo, mesoderm; from some tissue types
- 2. postnatal sourced cells (cord blood, fat, and teeth) can mineralize and create soft tissues
When was postnatal stem cell therapy launched?
1968, first allogenic bone marrow transplant
First stem cell research?
1954 Nobel Prize to John Enders, growing polio virus in human embryonic kidney cells
Where can autologous stem cells be harvested from?
Bone marrow, peripheral blood, fat removed by liposuction, periodontal ligament, oral mucosa, skin
What is an autologous cell bank, example?
Umbilical cord stem cells
What are the most valuable stem cells?
Neuronal differentiation; with the right induction factors these can become adipogenic, chondrogenic, myogenic, and osteogenic cells
What are the most promising cells for endodontic regeneration?
Autologous postnatal stem cells
Examples of allogeneic donor cells:
- 1. blood cells for transfusion
- 2. bone marrow cells
- 3. donated egg cells
What is the disadvantage to allogenic stem cells?
risk of immune rejection and pathogen transmission (same for xenogeneic cells)
stem cells from human exfoliated deciduous teeth
Sometimes pulp stem cells are called ___________ cells because these cells appear to synthesize and secrete _______ matrix like the ___________ cells they replace
Stem cells from apical papilla
dental follicle progenitor cells
What do SHED, SCAP, and DFPC share?
ability to give rise to osteogenic, chondrogenic, adipogenic, myogenic, and neurogenic cells
What is the purpose of the odontoblastoid cells (dental pulp stem cells)?
a odontoblast supporting role because without these the odontoblasts do not survive
Stem cells can be identified and isolated from mixed cell populations by four techniques:
- 1. fluorescent antibody cell sorting (FACS) used with CD34 (protein marker)
- 2. immunomagnetic bead selection
- 3. immunohistochemical staining
- 4. physiologic and histologic criteria
What do human dental pulp stem cells express?
- von Willebrand factor CD146
- α-smooth muscle actin
- 3G5 proteins
Activity of NGF (nerve growth factor) and source
critical for survival and maintenance of sympathetic and sensory neurons
secreted by neuron's target
Activity of TGF-α and source
Induces epithelia and tissue structure development
macrophages, brain cells, and keratinocytes
Activity of PDGF and source
growth of connective tissue, glial, and smooth muscle
platelet, endothelial cells, placenta
FGF (fibroblast growth factor) and source
promotes proliferation of many cells
EGF (epidermal growth factor) activity and source?
prolif of mesenchymal, glial, and epithelial cells
submaxillary gland and Brunner gland
TGF-β activity and source?
anti-inflammatory, promotes wound healing, inhibits macrophage and lymphocyte proliferation
dentin matrix, TH1 cells, NKC
BMP activity and source?
differe of dental pulp stem cells into odontoblastoid cells
Application of rhIGF (insulin) with ________ has been found to induce complete _____ ________ and ________ _______ formation
- dentin bridging
- tubular dentin
In development of regenerative endondontic techniques what are the 3 major areas of research?
- 1. postnatal stem cell therapy (harvest)
- 2. dental pulp constructs (scaffold)
- 3. root canal revascularization (disinfection)
What is the simplest method to administer cells of appropriate regenerative potential?
Inject the postnatal stem cells into disinfected root canal systems after the apex is opened wide enough for vascularization
In the human body where can post natal stem cells be obtained?
- 1. Skin
- 2. Buccal mucosa
- 3. fat
- 4. Bone
What are some approaches of obtaining postnatal stem cells capable of differentiating into the diverse cell populaiton of the pulp?
- 1. Autologous (Umbilical cord)
- 2. Allogeneic
- 3. Xenogeneic
NO Purified dental pulp stem cell lines are available
Name some advantages of using autologous post natal stem cells?
- 1. Disease free
- 2. Easy to harvest and deliver
- 3. Already used in bone marrow transplant
What are some disadvantages of injection delivery of postnatal stem cells?
- 1. cell may have low survival
- 2. migration to other parts of body (mineralization there)
- 3. do not produce new functioning pulp
Dental pulp stem cells must be organized into _____-________ ________ that can support cell organization and ____________
- three dimensional
Dentin chips and dental pulp constructs?
Found to stimulate reparative dentin bridge formation
May provide matrix for stem cell attachment
What are some requirements to scaffolds for stem cells?
- 1. Biodegradability
- 2. High porosity/adequate pore size
- 3. Rate of degradation
Name some synthetic materials used for scaffolding. Drawbacks?
- 1. Polylactic Acid
- 2. Polyglycolic Acid
- 3. Polycaprolactone
No high porosity or regular pore size
Name some non-synthetic materials used for scaffolding.
- 1. Collagen or fibrin
- 2. Polysaccharidic materials
- a. Chitosan or glycosaminoglycans
What is a soft 3D scaffold matrix?
Polymer hydrogel, injectable by syringe
What were past problems with hydrogels?
limited control over tissue formation and development
photopolymerizable ones are in research
Revascularization method assumes that the root canal space has been ________ and that the formation of a ______ ____ forms a ______ (_______) that traps cells capable of generating new tissue.
- blood clot
- matrix (fibrin)
Which antibiotics have shown to be useful in disinfection during revascularization?
Mixture of ciprofloxacin ,metronidazole, and minocycline (also CaOH can be used)
How does tetracycline enhance the growth of host cells?
Exposes embedded collagen fibers or growth factors
What are the advantages to revascularization?
simple, cheap, no need for biotech
own blood cells used, no rejection/pathogens
What are some concerns of revascularization?
Research can't find source of regenerated issue from blood clot
Enlarging the apex but allows for angiogensis, but coronal pulp may become hypoxic (possible necrosis)
What are the disadvantages of using a dental pulp construct for regenerative therapy?
Low cell survival
must be engineered to fit root canal precisely
What are the major research priorities in developing regenerative endodontic techniques? (List 5)
- 1. Improve disinfection and shaping
- 2. Improve smear layer removal
- 3. Engineer functional pulp tissue
- 4. Improve delivery methods
- 5. Measure clinical outcome
Dental pulp stem cells will readily attach and grow on ______ and _______ root canal systems, but none, or very few will ______ to ___________.
- cleaned and shaped
- smear layer
What do stem cells need to attach and adhere to root canal dentin?
must be supported within a polymer or collagen scaffold
How thick can the smear layer be on the dentin wall?
What is the smear layer comprised of?
- odontoblastic processes
- inorganic contaminants
Other than EDTA what other solutions have been promissing in removing smearl layer?
- Tetracycline isomer
- citric acid
What is MTAD?
Aqueous solution of 3% doxycycline hyclate (opposed to monohydrate, has improved water solubility, broad spectrum), 4.25% citric acid, .5% polysorbate 80 detergent
The most promising delivery method for regenerative endodontic procedures is:
autologous stem cells from oral mucosa
What growth factors would be used in scaffolds for regeneration of pulp tissue?
rhBMP-2,4,7 and TGF-β1,2,3
What are niches for stem cells?
Places that regulate how they participate in tissue generation, maintenance, and repair