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J Endod 2008;36:536–541. Before 2004 : Apexification : Apexification has proven to be highly predictable increased susceptibility to cervical fracture . The artificial apical barrier technique The material of choice : MTA The technique is predictable and successful .

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slide3
Before 2004 :

Apexification :

  • Apexification has proven to be highly predictable
  • increased susceptibility to cervical fracture
slide4
The artificial apical barrier technique
  • The material of choice : MTA
  • The technique is predictable and successful

Mineraltrioxideaggregate (MTA) was introduced in 1993 by Loma Linda University, the commercial version of MTA introduced in 1998

tooth-colored MTA was introduced in 2002

slide5
Banchs and Trope

2004

first revascularization research efforts :

  • immature tooth was treated with irrigation and disinfection using two antimicrobial agents (metronidazole and ciprofloxacin) with successful revascularization
tissue engineering
Tissue engineering
  • Stem Cell Therapy
  • Gene Therapy

Reference

key elements of tissue engineering
key elements of tissue engineering
  • stem cells
  • Morphogens or Signaling molecules
  • scaffold of extracellular matrix
adult stem progenitor cells
Adult Stem/Progenitor Cells
  • they exist as undifferentiated cells and maintain this phenotype
  • they have an ability to self-replicate for prolonged periods
  • they maintain their multiple differentiation potential throughout the life of the organism

Reference

Barry FP. Biology and clinical applications of mesenchymal stem cells. Birth Defects Res Part C, Embryo Today Rev 2003;69:250 –6.

stem cell plasticity
Stem cell plasticity
  • capacity and potential for adult stem cells to differentiate into a wider spectrum of phenotypes
  • fusion of stem cells with endogenous tissue-specific cells
stem cells of dental origin
Stem cells of dental origin
  • dental pulp stem cells (DPSCs)
  • stem cells from human exfoliated deciduous teeth (SHED)
  • stem cells from the apical papilla
  • dental follicle progenitor cells
  • periodontal ligament stem cells
scaffold
Scaffold
  • biological three-dimensional microenvironment for cell growth and differentiation
  • promoting cell adhesion, and migration.
  • serves as a carrier for morphogen in protein therapy
scaffold1
Scaffold
  • should be effective for transport of nutrients, oxygen, and waste.
  • It should be gradually degraded and replaced by regenerative tissue
  • They should have biocompatibility, nontoxicity, and proper physical and mechanical strength
signaling molecules
Signaling molecules

The morphogenetic signaling networks include the five major :

  • bone morphogenetic proteins (BMPs),
  • fibroblast growth factors (FGFs)
  • wingless and int-related proteins (Wnts)
  • Hedgehog proteins (Hhs)
  • tumor necrotic factor (TNF) families

Although five distinct families of morphogens are involved in

embryonic tooth development, BMPs appear to be sufficient for tooth

regeneration in adults

signaling molecules1
Signaling molecules
  • BMP2, BMP4, BMP6, BMP7, and Gdf11 are also expressed during odontoblast differentiation
  • BMP4 and Bmp5 during ameloblastdifferentiation
signaling molecules2
Signaling molecules
  • There are many similarities between morphogenic factors regulating dentinogenesis and the factors that regulate reparative dentinogenesis
  • transforming growth factor ß, (BMPs), platelet-derived growth factor, fibroblast growth factor, and vascular endothelial growth factor (VEGF) are incorporated into the dentin matrix duringdentinogenesis and are retained there As “fossilized” molecules.
signaling molecules3
Signaling molecules
  • interestingly, calcium hydroxide has been shown to solubilize Dentin and allow The release Of bioactive molecules that can potentially regenerate dentin.
slide19
Sakai VT, Zhang Z, Dong Z, Neiva K, Machado M, Shi S, SantosC, Nör JE. SHED differentiate into functional odontoblasts andendothelium. J Dent Res 2010;89:791–6.
  • Vasculogenesis
  • recently observed that SHED have the potential to differentiate into functional vascular endothelial cells via a process that closely resembles that of vasculogenesis
  • VEGF induces the differentiation of DPSCs (i.e., SHED) into endothelial cells

Reference

nerve regeneration
Nerve Regeneration
  • It is noteworthy that members of the BMP family have pronounced effects on neurogenesis
  • Thus, it is likely BMPs can be used for regenerative pulpal therapy and dentinogenesis may have concurrent beneficial effects on nerve regeneration.

Lein P, Guo X, Hedges AM, Rueger D, Johnson M, Higgins D. The effects of extracellular matrix and osteogenic protein-1 on the morphological differentiation of rat sympathetic neurons. Int J Dev Neurosci 1996;14:203–15.

Adler J, Jayan A, Melia CD. A method for quantifying differential expansion within hydrating hydrophilic matrixes by tracking embedded fluorescent microspheres. J PharmSci 1999;88:371–7.

Mabie PC, Mehler MF, Kessler JA. Multiple roles of bone morphogenetic protein signaling in the regulation of cortical cell number and phenotype. J Neurosci 1999; 19:7077– 88.

White PM, Morrison SJ, Orimoto K, Kubu CJ, Verdi JM, Anderson DJ. Neural crest stem cells undergo cell-intrinsic development changes in sensitivity to instructive differentiation signals. Neuron 2001;29:57–71.

References

complication
Complication
  • There is a risk of unfavorable transformation of the stem cells, and there is also a risk of unwanted contamination of these cells with pathogens during these procedures.
slide22
The field of stem cell-based regenerative dentistry is complex and multidisciplinary by nature. Progress will depend on the collaboration between clinicians and researchers from diverse fields (e.g., biomaterials, stem cell biology, endodontics) working together toward the goal of developing biological approaches to regenerate dental and craniofacial tissues.
treatment procedure
Treatment procedure

J Endod 2012;38:1428–1434

  • begins with chemical disinfection by copious irrigation of the root canal space with NaOCl, combination of NaOCl/chlorhexidine or NaOCl/hydrogen peroxide
  • followed by placement of an intracanal medicament at the first visit. Several medicaments like triple antibiotic mixture (metronidazole, ciprofloxacin, and minocycline), calcium hydroxide, and formocresol have been used successfully.

At the next visit

  • which should be at least 1 week after the initial session or more
  • in the absence of clinical signs of inflammation, the clinician removes the intracanal medicament
  • induces bleeding inside the root canal space by irritating the periradicular tissue.
  • After clot formation, the clinician seals the root canal space by placing an MTA plug over the blood clot
slide26
An 11-year-old boy
  • maxillary second premolar tooth had been accidently extracted and immediately replanted developed pulpal
  • necrosis and symptomatic apical periodontitis.
  • After preparing an access cavity, its necrotic pulp was removed. The canal was irrigated with 5.25% NaOCl solution and dried with paper points. A triple antibiotic mixed with distilled water was packed in the canal and left for 22 days.
slide27
Twenty milliliters of whole blood was drawn from the patient’s forearm for preparation of PRP.
  • After removal of the antibiotic mixture, the PRP was injected into the canal space up to the cementoenamel junction level. Three millimeters of grey mineral trioxide aggregate was placed directly over the PRP clot.
  • Three days later, the tooth was double-sealed with permanent filling materials.
results
RESULTS
  • Clinical examination 5 1/2 half months later revealed no sensitivity to percussion or palpation tests.
  • Radiographic examination of this tooth showed resolution of the periapical lesion, further root development, and continued apical closure.
  • Sensitivity tests with cold and an electric pulp test elicited a positive response similar to those found in the first premolar tooth
unfavorable outcomes
Unfavorable outcomes

J Endod 2012;38:1428–1434

  • Discoloration : use of minocycline in the triple antibiotic paste
  • Treatment Period: The required time for disinfection of the root canal space with triple antibiotic paste or calcium hydroxide and increased number of clinical sessions
unfavorable outcomes1
Unfavorable outcomes
  • Challenging Histologic Outcomes: generated tissue inside the root canal space after regenerative endodontic treatment was basically ingrowth of periodontal connective tissue instead of pulpal connective tissue.
  • No odontoblastic cell layer,dentin-like structure, and pulp-like tissue were detected
  • 3 types of tissues: cementum-like tissue that was responsible for increase in root length and thickness, bone-like tissue and periodontal ligament (PDL)–like tissue inside the canal space
unfavorable outcomes2
Unfavorable outcomes
  • Poor Root Development :absence of increase in root wall thickness , or lack of formation of tooth apex
  • Insufficient Bleeding
  • Root Canal Calcification/Obliteration
slide35
A healthy 14-year-old female
  • history of impact trauma to the anterior maxillary teeth 6 years before initial visit
  • Clinical examinations revealed extensive caries of tooth #8
  • Both teeth showed normal mobility
  • Cold test by using Endo-Frost cold spray did not elicit any response in maxillary central incisors
  • whereas maxillary lateral incisors responded normally to the test
  • maxillary central incisors were sensitive to percussion and palpation
slide37
After local anesthesia with 3% plain mepivacaine
  • access cavities on teeth #8 and #9 were prepared
  • Each root canal was passively irrigated with 20 mLNaOCl 5.25% without instrumentation, Canals were gently dried with paper points
  • A triple antibiotic mixed with distilled water was packed in the canal and left for 4 weeks
  • A sterile size 40 K-file was overextended and initiate bleeding
  • approximately 3 mm of MTA was placed in the coronal third of the canals
slide39
The patient was recalled yearly
  • The teeth were not sensitive to percussion and palpation.
  • The response to the cold test was negative in all follow-up sessions.
  • In radiographic examinations the radiolucent lesions healed, and the apices formed.
  • However, there was no increase in the length and thickness of the roots
slide40
Six years after initial treatment the patient complained about the appearance of her maxillary central incisors.
  • severity of discoloration, full crown restoration for both teeth was suggested
  • root canal therapy of both central incisors
slide42
In the present case, passage of a long time (6 years) without any treatment after traumatic impact might be related to damaged Hertwig epithelial root sheath and, subsequently, decreased root development potential
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