apical regeneration ppt

SEMINAR ON

APICAL REGENERATION

Presented by:

Astha Jaikaria

Deptt. of Pediatric and Preventive Dentistry

6/1/2017 1

INDEX:

INTRODUCTION

DEFINITIONS

-HISTORY

-FACTORS GOVERNING REGENERATIVE

ENDODONTIC PROCEDURES

-PULP REGENERATION

-POSSIBLE REGENERATIVE

ENDODONTIC PROCEDURES

-NOVEL APPROACH TOWARDS APICAL

REGENERATION

-CHALLENGES IN APICAL

REGENERATION

-CONCLUSION

-REFERENCES6/1/2017 2

Introduction

Irreversible damage to immature permanent teeth as a result of

noxious infection or local trauma before normal physiological closure

of the apical structure represents a real clinical challenge.

One of the major risks facing immature teeth with interrupted root

development is weakened fracture resistance of the dentin walls.

Important requirement for regeneration of pulp tissues is to obtain

stem cells capable of differentiating into odontoblasts.6/1/2017 3

Regenerate a functional pulp-dentin complex within a

patient’s existing permanent tooth.

Helps restore natural functions:-formation of

replacement dentin and maintenance of tissue immunity

and neural sensation.

6/1/2017 4

Nakahara has summarized potential methods for regenerating

an entire tooth.

•First approach -incorporating principles of tissue engineering,

involves seeding appropriate stem cells onto scaffolding materials, such

as has been used for periodontal regeneration, controlled by the

addition of specific growth factors and/or signaling molecules.

•Second approach - replicating the natural developmental processes

of embryonic tooth formation - Artificial tooth germs are transplanted

into the bodies of animal hosts where there is enough blood flow to

support tissue formation.

6/1/2017 5

DEFINITIONS:

Regenerative endodontics has been defined as biologically based

procedures designed to replace damaged structures such as dentin,

root structures, and cells of the pulp-dentin complex.(Cohen)

Revascularization describes reestablishment of vascular supply to

immature permanent teeth. (Andreasen JO and Andreasen FM)

Revitalization describes ingrowth of vital tissue that does not

resemble the original lost tissue.

Regeneration is a biologic process whereby the continuity of the

disrupted or lost tissue is regained by new tissue which restores

structures and function.6/1/2017 6

Endodontic regeneration is the replacement of “damaged structures,

including dentin and root structures, as well as cells of the pulp-

dentin complex.”

It also indicates that the pulp is completely necrotic (complete

degradation) and a tissue (pulp like) must be formed that may function

as the original tissue.

Maturogenesis has been defined as physiologic root development,

not restricted to the apical segment.Weisleder et al (2003)

6/1/2017 7

Apexogenesis, is defined as a vital pulp therapy procedure

performed to encourage continued physiologic development and

formation of the root end.

An important distinction is that apexogenesis is indicated

for teeth in which there has been no loss of vascularity, --

no need to “revascularize” the canal space.

6/1/2017 8

HISTORY:

Rule and Winter(1966) documented root development and apical

barrier formation in cases of pulpal necrosis in children.

Nygaard- Ostby & Hjortdal(1971) performed studies that can be

considered the forerunner of pulpal regeneration.

Myers and Fountain in 1974 attempted to regenerate dental pulp with

blood clot filled in the canal.

Skoglund et al (1978) demonstrated that in a traumatic avulsion, blood

vessels slowly grow from apex toward the pulp horn by replacing the

necrosed pulp left behind after the avulsion injury.6/1/2017 9

Kling M et al (1986) - incidence of revascularization was enhanced

by 18%, if the apex showed radiographic opening of more than 1.1

mm.

Age is an important issue since some clinical studies suggest that

younger patients have a greater healing capacity or stem cell

regenerative potential.

Dental pulp tissue engineering was first tested by Mooney’s group

(1996)

6/1/2017 10

Bohl KS (1998) described a tissue engineering approach to dental

pulp tissue replacement utilizing cultured cells seeded upon synthetic

extracellular matrices.

Huang et al (2006): isolated human pulp stem cells may differentiate

into odontoblasts on dentin in vitro.

6/1/2017 11

FACTORS GOVERNING REGENERATIVE

ENDODONTIC PROCEDURES:

(1) Stem cells that can differentiate and support the

continued root development.

(2) Growth factors for induction of cellular proliferation and

differentiation.

(3) Appropriate scaffold to promote cellular growth and

differentiation.

6/1/2017 12

6/1/2017 13

Regenerative endodontics includes:

Root canal revascularization via blood clotting.

Stem-cell therapies such as :

Post-natal stem-cell therapy

Pulp implantation

Scaffold implantation

Injectable scaffold delivery

Three-dimensional cell printing

Gene delivery

6/1/2017 14

Pulp tissue-engineering triad

Triad diagram

6/1/2017 15

Stem Cells

Pulpal mesenchymal stem cells: localized in the perivascular region

and the cell-rich zone of Hohl adjacent to the odontoblastic layer may

serve as cell sources for replacement odontoblasts.

Local release of angiogenic growth factors such as vascular

endothelial growth factor (VEGF) and platelet-derived growth factor

(PDGF).

Platelet-rich plasma has about a three- to sixfold increase in VEGF

and PDGF.

6/1/2017 16

Types of stem cells

Stem cell type Cell Plasticity Source of stem cell

Totipotent Each cell can developinto a new individual

Cells from early (1–3 days) embryos

Pluripotent Cells can form any (over 200) cell types

Some cells of blastocyst (5–14 days)

Multipotent Cells differentiated, but can form a number of other tissues

Fetal tissue, cord blood, and postnatal stem cells includingdental pulp stem cells

6/1/2017 17

Five different types of postnatal mesenchymal stem

cells have been reported to differentiate into

odontoblast-like cells:

Dental pulp stem cells (DPSC)

Stem cells of human exfoliated deciduous teeth (SHED)

Stem cells of the apical papilla (SCAP)

Dental follicle progenitor cells(DFPC)

Bone marrow-derived mesenchymal stem cells(BMMSC)

Cells that express mineralized nodules and DSP as

odontoblast-like.6/1/2017 18

Growth Factors/Morphogens

Trigger the differentiation of selected mesenchymal stem cell

populations into odontoblast-like cells.

Application of dexamethasone greatly increased the differentiation

of human dental pulp cells into odontoblast-like cells.

Unlikely that a single growth factor will result in maximal

differentiation.

TGF-β1 is the only TGF subtype detectable in human dentin.

6/1/2017 19

EDTA strongly exposed immunoreactive TGF-β1 from human

dentin, with appreciably smaller activities released after treatment

with Ca(OH)2, NaOCl, MTA, or citric acid.

Other growth factors:-

Bone morphogenetic protein (BMPs)

platelet-derived growth factor (PDGF)

transforming growth factors (TGFs)

fibroblast growth factors (FGFs)and

growth/differentiation factor 11 (Gdf11).

6/1/2017 20

6/1/2017 21

Factor Primary Source Activity Usefulness

Bone morphogeneticproteins

Bone matrix BMP induces differentiation ofosteoblasts andmineralization of bone

BMP is used to make stemcells synthesize andsecrete mineral matrix

Colony stimulatingfactor

A wide range of cells

CSFs are cytokines thatstimulate the proliferationof specific pluripotent bonestem cells

CSF can be used to increasestem cell numbers

Epidermal growthfactor

Submaxillary glands EGF promotes proliferation ofmesenchymal, glialandepithelial cells

EGF can be used toincrease stem cellnumbers

6/1/2017 22


Fibroblast growthfactor

A wide range of cells FGF promotes proliferation ofmany cells

FGF can be used to increasestem cell numbers

Insulin-like growthfactor-I or II

I - liver II–variety of cells

IGF promotes proliferation ofmany cell types

IGF can be used to increasestem cell numbers

Interleukins IL-1 toIL-13

Leukocytes IL are cytokines whichstimulate the humoral andcellular immune responses

Promotes inflammatory cellactivity

6/1/2017 23


Nerve growth factor A protein secreted by aneuron’s target tissue

NGF is critical for the survivaland maintenance ofsympathetic and sensoryneurons.

Promotes neuronoutgrowth and neuralcell survival

Transforminggrowth factor-beta

Dentin matrix, activatedTH1 cells (T-helper) andnatural killer (NK) cells

TGF- is anti-inflammatory,promotes wound healing,inhibits macrophage andlymphocyte proliferation

TGF-1 is present in dentinmatrix and has beenused to promotemineralization of pulptissue

6/1/2017 24


Platelet-derivedgrowth factor

Platelets, endothelial cells,placenta

PDGF promotes proliferationof connective tissue, glialand smooth muscle cells

PDGF can be used toincrease stem cellnumbers

Transforminggrowth factoralpha

Macrophages, brain cells,and keratinocytes

TGF- may be important fornormal wound healing

Induces epithelial andtissue structuredevelopment

6/1/2017 25

Scaffolds

Appropriate scaffolding is necessary to:

(1) provide a spatially correct position of cell location

(2)regulate differentiation, proliferation, or metabolism.

Extracellular matrix molecules control the differentiation of stem

cells

Appropriate scaffold might selectively bind and localize

cells,contain growth factors and undergo biodegradation over time.6/1/2017 26

Scaffolds can be classified as - natural or synthetic.

Examples of natural scaffolds :

collagen

glycosaminoglycans

demineralized or native dentin matrix

fibrin.

PRP is autologous, fairly easy to prepare in a dental setting, rich in

growth factors,degrades over time, and forms a three-dimensional

fibrin matrix.

6/1/2017 27

Fibrin polymer of the blood clot likely serves as a matrix, or scaffold,

for stem cell growth - tissue regeneration

Examples of synthetic materials :

polylactic acid (PLA)

polyglycolic acid (PGA)

polylactic-coglycolic acid (PLGA)

polyepsiloncaprolactone

hydroxyapatite/tricalcium phosphate

bioceramics

titanium

hydrogels such as alginate or variants of polyethylene glycol (PEG).6/1/2017 28

Delivery System

Resultant mixture must be delivered in a spatially appropriate fashion

into the space of the root canal system.

One approach:

Inject a cell/scaffold/growthfactor mixture into the apical 1

mm of the root canal system and then “back-fill” the root canal system

with a scaffold/growth-factor combination.

6/1/2017 29

PULP REGENERATION

Pulp necrosis of an immature permanent tooth - arrests further

development , leaves the tooth with thin, weak walls ,prone to

fracture.

Traditional treatment for these teeth :

Long-term calcium hydroxide application to induce apexification (an

apical hard tissue barrier)

Artificial barrier of MTA

Do not increase the fracture resistance of the walls.

6/1/2017 30

Revascularization focuses on :

Inducing bleeding into an empty root canal space - trigger

a process similar to the role of the blood clot in triggering

wound healing.

Rationale of revascularization -

If a sterile tissue matrix is provided in which new cells can

grow, pulp vitality can be reestablished.

Key factor for the success : disinfection of the root canal

system.

6/1/2017 31

Possible regenerative endodontic

procedures

a) Root canal revascularization via blood clotting

b) Postnatal stem cell therapy

c) Scaffold implantation

d) Three-dimensional cell printing

e) Gene delivery

• Most of these technologies are hypothetical and do not

currently have FDA approval for use in patients.

6/1/2017 32

a) Root canal revascularization via

blood clotting

No evidence-based guideline that can be established.

Revascularization should be considered for:

-Incompletely developed permanent tooth that has an open apex

-Large diameter of the immature (open) apex may foster the ingrowth of

tissue into the root canal space

**Indicative of a rich source of mesenchymal stem cells of the apical

papilla (SCAP) .

Revascularization protocol

Case selection:

6/1/2017 33

Disinfection protocol

Immature permanent tooth -the apex is not fully developed and

often has a blunderbuss shape.

Thin, fragile dentinal walls that may be prone to fracture during

instrumentation or obturation.

Open apex increases the risk of extruding material into the

periradicular tissues.

6/1/2017 34

Excessive instrumentation and dressing using cytotoxic antiseptics

may remove:

-pulp tissue that can survive in the wide, well nourished apical area

- the cells capable of forming pulp and dentin.

Lack of instrumentation would also be effective to have the benefit of

avoiding a smear layer that could occlude the dentinal walls or

tubules.

Solely relies on irrigants and intracanal medicaments.

6/1/2017 35

Irrigants

2.5–5.25% NaOCl

3% hydrogen peroxide

Povidine-iodine

-0.12%-2% CHX. - may be detrimental to the stem cells.

6/1/2017 36

Intracanal medicaments

Triple antibiotic paste (a 1:1:1 mixture of ciprofloxacin/

metronidazole/ minocycline or variation), Ca(OH)2 alone or in

combination with antibiotics or formocresol.

Calcium hydroxide as an intra-canal medicament for

revascularization - damages the remaining pulp tissue, apical papilla

and HERS.

*Will induce the formation of a layer of calcific tissue which may

occupy the pulp space - preventing the pulp tissue to regenerate into that

space.6/1/2017 37

Composition and mixing instructions

for the antibiotic paste (adapted from

Hoshino et al. 1996)

3- Mix- MP

· Antibiotics (3 Mix)

· Ciprofloxacin 200 mg

· Metronidazole 500 mg

· Minocycline 100 mg

· Carrier (MP)

· Macrogol ointment

· Propylene glycol

6/1/2017 38

Protocol for preparation

Antibiotics (3 Mix) – do not cross- contaminate.

Remove sugar coating from tablets with surgical blade,

crush individually in separate mortars.

Open capsules, crush in individually in separate mortars.

Grind each antibiotic to a fine powder.

Combine equal amounts of antibiotics (1:1:1) on mixing

pad.

6/1/2017 39

Carrier (MP)

Equal amounts of macrogol ointment and progylene glycol

(1:1)

Using clean spatula, mix together on pad.

Result should be opaque.

1:5 (MP : 3 Mix) → creamy consistency.

1:7 (standard mix) → smears easily but does not crumble

If result is flaky or crumbly, then too much 3 mix has been

incorporated.6/1/2017 40

Storage

Antibiotics must be kept separately in moisture-tight

porcelain containers.

Macrogol ointment and propylene glycol must be stored

separately.

Discard if mixture is transparent (evidence of moisture

contamination)

6/1/2017 41

Metronidazole (nitroimidazole

compound)

Activity against :

protozoa and anaerobic bacteria

gram-negative and gram-positive bacilli.

Permeates bacterial cell membranes binds to the DNA,

disrupting its helical structure - rapid cell death.

6/1/2017 42

Tetracyclines(doxycycline and

minocycline)

Bacteriostatic antimicrobials.

-Activity against:

gram-positive and gram-negative microorganisms,most spirochaetes,

and many anaerobic and facultative bacteria.

-Gain access to bacterial cells by -diffusion through the outer

membrane followed by active transport through the inner membrane.

-Act by inhibiting protein synthesis on the surfaces of ribosomes.

-Minocycline(semisynthetic derivative of tetracycline) - similar

spectrum of activity.

Available in many topical forms-gel mixtures to sustained release

microspheres.6/1/2017 43

Ciprofloxacin (synthetic

floroquinolone)

Bactericidal mode of action.

Acts through the inhibition of DNA gyrase, resulting in

degradation of the DNA by exonucleases.

Bactericidal activity persists during the multiplication and

resting phase of the bacterium.

Very potent activity against gram-negative pathogens.

Very limited activity against gram-positive bacteria.6/1/2017 44

Clinical protocol

First appointment:

Treatment alternatives, risks, and potential benefits should be

described to the patient and guardian.

Following informed consent, the tooth is anesthetized, isolated, and

accessed.

Minimal instrumentation should be accomplished, use a small file to

“scout” the root canal system and determine working length.

If sensation is experienced within the canal system - some residual

vital pulp tissue remains.6/1/2017 45

6/1/2017 46

Second appointment:

Patient is evaluated for resolution of any signs or symptoms of an

acute infection (e.g., swelling, sinus tract pain, etc.)

Antimicrobial treatment is repeated if resolution has not occurred. In

most cases, the acute signs and symptoms have resolved.

Following isolation and reestablishment of coronal access, the tooth

should be copiously and slowly irrigated with 20 ml NaOCl, possibly

together with gentle agitation with a small hand file to remove the

antimicrobial medicament.

6/1/2017 47

6/1/2017 48

If after several rounds of intra-canal irrigation and

medication the clinical symptoms show no sign of

improvement, i.e., persistent presence of sinus tract,

swelling and/or pain,

apexification procedure should then be carried out.

Blood clot acts as a scaffold and source of growth factors

to facilitate the regeneration and repair of tissues into the

canal.

6/1/2017 49

6/1/2017 50

Outcome

Given a condition that is free of infection, many tissues are

programmed and capable of self-regeneration.

Wang X et al (2010) -investigate the type of tissue actually generated

in the pulp space of immature dog teeth with apical periodontitis after

revascularization.

Histologic examination for tissues generated in the canal space:

(1) intracanal cementum (IC) along the dentinal walls causing the

thickening of the root,

(2)bonelike tissue termed intracanal bone (IB),

(3)PDL-like tissue.

*Summarized that the tissues were not pulp parenchymal tissues and

that they did not function like pulp tissue.6/1/2017 51

Advantages of revascularization over

conventional apexification/

apexogenesis treatment methods.

Classic treatment options for immature, nonvital teeth

included:

surgical endodontics

apexification with calcium hydroxide

single visit mineral trioxide aggregate plug.

6/1/2017 52

Limitations of surgical endodontics:

Invasive procedure

-Possibility of surgical complications

-Increased cost of treatment and possible

psychological distress

-Compromised crown:root ratio

6/1/2017 53

Limitations of calcium hydroxide–

induced apexification :

It might require 6 –24 months for barrier formation.

-The barrier formed is often porous and not continuous or compact - requires

obturation of the canal after barrier formation, with all its inherent problems of

achieving a fluid-tight seal without splitting the tooth.

Further development of the root does not take place.

Intracanal calcium hydroxide dressing can also make the tooth brittle - its

hygroscopic and proteolytic properties.

High pH is known to be toxic to vital cells and might damage the cells in its

contact at the apex, which have regenerative capacity to heal periapical tissues.

-By filling the canal with calcium hydroxide, a physical barrier is created that

prevents migration of multipotent undifferentiated mesenchymal cells into the

canal and regeneration of tissues at the lateral dentinal walls.6/1/2017 54

Advantages of placement of an apical

plug of MTA and gutta-percha filling:

MTA is a biocompatible material.

Has osteoinductive properties.

Sets in the presence of moisture, and the treatment can be

completed in a single sitting.

Limitations:

It does not strengthen the remaining tooth structure.

6/1/2017 55

Advantages of revascularization:

Requires a shorter treatment time- after control of infection,can be

completed in a single visit.

Cost-effective- the number of visits is reduced, and no additional

material (such as TCP, MTA) is required.

Obturation of the canal is not required unlike in calcium hydroxide–

induced apexification, with its inherent danger of splitting the root

during lateral condensation.

-Continued root development (root lengthening) and strengthening of

the root as a result of reinforcement of lateral dentinal walls with

deposition of new dentin/hard tissue.6/1/2017 56

Technically simple and can be completed using currently

available instruments and medicaments without expensive

biotechnology.

Regeneration of tissue in root canal systems by a patient’s

own blood cells avoids the possibility of immune

rejection and pathogen transmission from replacing the

pulp with a tissue engineered construct.

6/1/2017 57

Limitations of revascularization:

Long-term clinical results are as yet not available.

-Entire canal might be calcified, compromising esthetics

and potentially increasing the difficulty in future

endodontic procedures if required.

In case post and core are the final restorative treatment

plan, revascularization is not the right treatment option

because the vital tissue in apical two thirds of the canal

cannot be violated for post placement.

6/1/2017 58

Concentration and composition of cells trapped in fibrin

clot is unpredictable, which may lead to variations in

treatment outcomes.

Enlargement of the apical foramen is necessary to promote

vascularizaton and to maintain initial cell viability via

nutrient diffusion.

Reimplantation of avulsed teeth with an apical opening of

approximately 1.1 mm demonstrate a greater likelihood of

revascularization.

6/1/2017 59

b) Postnatal stem cell therapy

Stem cells and pulp tissue regeneration

Stem cells may have characteristics of totipotency,

pluripotency or multipotency.

Two main stem cell categories:

embryonic and postnatal.

6/1/2017 60

Embryonic stem cells: pluripotent cells that retain their ability to

differentiate into any cell type, while simultaneously maintaining

their initial undifferentiated state during cell cycles.

-Highly plastic : clearly due to their capacity to originate any kind of

specialized cell type and yet maintain their undifferentiated state-

pluripotent cells highly suitable for possible use in tissue

regeneration.

-Immunological and ethical problems associated with using allogenic

embryonic cells.

6/1/2017 61

Postnatal cells : multipotent and may be classified by

their origin—hematopoietic (HSC) or mesenchymal cells

(MSC)—or by their differentiation potential.

-Less plastic, have a limited life cycle, and are consequently

more restricted in their differentiation potential than

embryonic stem cells.

6/1/2017 62

Stem cells of dental origin

Postnatal dental pulp stem cells (DPSCs)

Stem cells obtained from deciduous teeth (SHED)

Periodontal ligament stem cells (PDLSCs)

Dental follicle progenitor stem cells (DFPCs)

Stem cells from the apical papilla (SCAP)

6/1/2017 63

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Dental follicle precursor cells(DFPCs)

DFPCs come from developing tissue, it is considered that they might

exhibit a greater plasticity than other DSCs.

Able to differentiate into odontoblasts in vitro, and four weeks after

combining rat DFPCs with treated dentin matrix the root-like tissues

stained positive for markers of dental pulp.

6/1/2017 65

Dental pulp stem cells (DPSCs):

• Characterized as clonogenic and highly proliferative

• Dentin and pulplike tissues were generated following the

transplantation of DPSCs in hydroxyapatite/tricalcium phosphate

(HA/TCP) scaffolds into immunodeficient mice.

• Play an important role in the balance of inflammation and

repair/dentinogenesis during invasive caries lesions or pulp

exposures.

• Shown to express the bacterial recognition toll-like receptors, TLR4

and TLR2, and vascular endothelial growth factor in response to

lipopolysaccharide.

6/1/2017 66

Stem cells from apical papilla(SCAP Cells)• Found in the apical papilla located at the apices of developing teeth at the junction

of the apical papilla and dental pulp.

• Apical papilla is essential for root development- refers to the soft tissue at the

apices of developing permanent teeth (Sonoyama et al., 2006, 2008) is more apical

to the epithelial diaphragm, and there is an apical cell-rich zone lying between the

apical papilla and the pulp.

• Clonogenic and can undergo odontoblastic/osteogenic, adipogenic, or neurogenic

differentiation.

• Seeded onto synthetic scaffolds consisting of poly-D,L-lactide/glycolide inserted

into tooth fragments, and transplanted into immunodeficient mice, induced a pulp

like tissue with well-established vascularity, and a continuous layer of dentin like

tissue was deposited onto the canal dentinal wall.

6/1/2017 67

http://jdr.sagepub.com/content/88/9/792.full

http://jdr.sagepub.com/content/88/9/792.full

Schematic representation of pulp regeneration.A)Immature, nonvital permanent tooth, showing the location

of the apical papilla with its rich collection of stem cells.

(B) Following medication of the canal with tri-antibiotic paste, the canal is over instrumented to encourage

bleeding up to the cervical level.Subsequent blood clot is overlaid with MTA and a sealing restoration and

forms a scaffold for invasion by SCAP cells.

(C ) Pulp regeneration is expected to allow continued root formation in a previously pulpless tooth. SCAP,

Stem cells from apical papilla.6/1/2017 68

Stem cells from human exfoliated deciduous teeth(SHED Cells)

Highly proliferative stem cells isolated from exfoliated deciduous

teeth capable of differentiating into a variety of cell types -

osteoblasts, neural cells, adipocytes, and odontoblasts, and inducing

dentin and bone formation.

Generate dentin-pulp like tissues with distinct odontoblast like cells

lining the mineralized dentin-matrix

Represent a more immature population of multipotent stem cells.

Transforming growth factor (TGF)-b, fibroblast growth factor

(FGF)2, TGF-b2, collagen (Col) I, and Col III, are more highly

expressed in SHED cells compared with DPSCs.6/1/2017 69

Periodontal ligament stem cells(PDLSCs)

• Seo and colleagues : the presence of clonogenic stem cells in

enzymatically digested PDL and further showed that human

PDLSCs transplanted into immunodeficient rodents generated a

cementum/PDL-like structure that contributed to periodontal tissue

repair. Later work showed that PDLSCs differentiation was

promoted by Hertwig’s epithelial root sheath cells in vitro.

• PDLSCs have the capability to differentiate into cementoblast like

cells, adipocytes, and fibroblasts that secrete collagen type I.

6/1/2017 70

Revascularization and stem cells

Stem cells in the vital pulp, apical papilla, periodontal ligament or

alveolar bone - source of tissue regeneration in the apical root region of

immature permanent teeth.

-Certain extracellular matrix proteins generated in this kind of

microatmosphere

e.g, laminin

Some chemiotactic factors, particularly sphingosine 1-phosphate (S1P)

and transforming growth factor b1 (TGF-b1)- potent stimulators of the

migration of dental pulp stem cells (DPSCs) to induce regeneration.

6/1/2017 71

c) Scaffold Implantation

In dental pulp regeneration, the ideal matrix should also ensure a

good neurovascular supply to the new pulp tissue.

e.g.,* use of DPSCs seeded on a 3D polyglycolic acid matrix and

grown in vitro

*collagen-based or alginate gel matrices.

-Soft matrix materials:

injectable hydrogels such as these self-assembling peptide termed

‘‘multidomain peptides’’ (MDPs) with a repetitive amphiphilic

peptide sequence able to form internal nets by self assembly- used

with DPSCs and SHED.6/1/2017 72

d)Three-Dimensional Cell Printing

In theory, an ink-jet-like device is used to dispense layers of cells suspended in a

hydrogel to recreate the structure of the tooth pulp tissue.

Three dimensional cell printing technique can be used to precisely position cells,

has the potential to create tissue constructs that mimic the natural tooth pulp tissue

structure.

Disadvantages:

-Construction of precise 3D models for each individual pulp cavity.

-Cell line needs to be grown and expanded before being implanted into the root

canal i.e,is time consuming.

-Effective delivery system will be required.

-Implanted tissue lacks a crucial vascular supply.

6/1/2017 73

e) Gene Therapy

Means of delivering genes for growth factors, morphogens,

transcription factors, extracellular matrix molecules locally to

somatic cells of individuals with a resulting therapeutic effect.

Gene can stimulate or induce a natural biological process by

expressing a molecule involved in regenerative response for the

tissue of interest.

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Precise delivery and efficient transfer of genes into target

tissue cells, prompt assessment of gene expression at

required times and appropriate levels and the minimization

of undesirable systemic toxicity are essential for successful

gene therapy.

Another approach could be to introduce mineralizing genes

in the pulp tissue to induce calcific tissue formation.

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Novel approach towards apical

regeneration

a)Treatment with calcium enriched mixture ( CEM )

b) Using soft tissue diode laser

Diode lasers are soft tissue lasers with a wavelength of 810980 nm.

Laser acts by ablation of the damaged pulp tissue in the immediate

vicinity of the beam, disinfection of the remnant tissue by bacterial

cell lysis and biostimulation of surrounding tissue, which promotes

healing.

6/1/2017 78

Challenges in Apical Regeneration

Disinfection and shaping of the root canals in a

fashion to permit regenerative endodontics:

In the presence of infection, the pulp stem cells that survive

appear to be incapable of mineralization and deposition of

tertiary dentin bridge.

Pulp stem cells, periodontal stem cells, and fibroblasts do

not adhere and grow in infected root canal systems.

6/1/2017 79

Creation of replacement pulp-dentin

tissue:

Source of pulp tissue may be from :

root canal revascularization

stem cell therapy, involving the delivery of autologous or allogenic

stem cells into root canals

pulp implantation, involving the surgical implantation of synthetic

pulp tissue grown in the laboratory.

Each of these techniques to regenerate pulp tissue will have

advantages and limitations -still have to be defined through basic

science and clinical research.6/1/2017 80

Delivery of replacement pulp-dentin

tissues:

Sterilization of scaffolds -

Biodegradable polymers pose some challenge to sterilization due to

their low thermal transition temperatures and their tendency to

hydrate.

6/1/2017 81

Nerve and vascular regeneration:

Some of the intrinsic difficulties of engineering dental pulps

are related to the anatomy and location of this tissue.

All vascular and neural supply to pulp tissue is provided

through a foramen located at one extremity, poses a challenge

for tissue engineering.

6/1/2017 82

Ageing and regeneration.:

Pulpal wound healing and regeneration may be compromised with

increasing age.

Measuring appropriate clinical outcomes:

Will not be possible to histologically investigate mineralizing

odontoblastoid cell functioning or nerve innervation.

Rely on the noninvasive tests in use.

6/1/2017 83

CONCLUSION

Provide an alternative to more traditional restorative

approaches because the diseased tissue is replaced by natural

tissue , which forms an integral part of the tooth.

Each one of the regenerative approaches has its own

advantages and limitations

Development of such approaches requires precise regulation

of the regenerative events if they are to be effective.

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