ABE Regenerative Endodontics 2 — Questions and Answers
Question 1: Stem cells of the apical papilla (SCAP) are considered the PRIMARY source of cells for root development during regenerative endodontic procedures. Where do SCAP reside?
- Within the periodontal ligament at the furcation
- In the loose connective tissue apical to the root apex in immature teeth (Correct answer)
- Along the cervical third of the root canal wall
- Within the pulp chamber of mature teeth
Correct answer: In the loose connective tissue apical to the root apex in immature teeth
SCAP are found in the apical papilla, a soft tissue mass apical to the developing root apex in immature teeth, and are thought to be the progenitor cells responsible for continued root formation.
Question 2: Which of the following correctly describes a KEY difference between apexification and regenerative endodontic procedures for treating necrotic immature teeth?
- Apexification uses a scaffold; REPs use MTA plug
- Apexification creates an apical barrier without continued root development; REPs aim for continued root maturation (Correct answer)
- REPs are indicated only in teeth with closed apices
- Apexification is preferred when apex diameter is less than 1 mm
Correct answer: Apexification creates an apical barrier without continued root development; REPs aim for continued root maturation
Apexification (with calcium hydroxide or MTA) creates an apical stop but does not increase root length or wall thickness; REPs aim to restore a biologically active tissue and allow continued root development.
Question 3: MTA (Mineral Trioxide Aggregate) is placed as a cervical plug in regenerative endodontic procedures primarily to:
- Stimulate angiogenesis in the blood clot scaffold
- Seal the coronal aspect over the scaffold and prevent bacterial leakage (Correct answer)
- Provide an antibacterial effect throughout the canal
- Encourage differentiation of SCAP into odontoblasts
Correct answer: Seal the coronal aspect over the scaffold and prevent bacterial leakage
The MTA cervical plug creates a hermetic coronal seal over the blood clot/scaffold, preventing coronal microleakage that could re-infect the regenerating tissue.
Question 4: In the AAE-recommended REP protocol, the second appointment (scaffold induction) should ideally be scheduled at least how long after the first appointment?
- 1–2 days
- 1–4 weeks (Correct answer)
- 3–6 months
- Immediately at the same appointment
Correct answer: 1–4 weeks
The AAE recommends waiting at least 1–4 weeks between disinfection and scaffold induction appointments to allow antibiotic paste to reduce bacterial load and confirm resolution of symptoms.
Question 5: Which growth factor found abundantly in dentin matrix plays a critical role in odontoblast differentiation and is released by EDTA conditioning during REPs?
- Vascular endothelial growth factor (VEGF)
- Transforming growth factor beta-1 (TGF-β1) (Correct answer)
- Platelet-derived growth factor (PDGF-BB)
- Fibroblast growth factor-23 (FGF-23)
Correct answer: Transforming growth factor beta-1 (TGF-β1)
TGF-β1 is the predominant growth factor sequestered in dentin matrix and is released upon EDTA demineralization; it potently drives odontoblast differentiation and pulp-dentin complex regeneration.
Question 6: A patient presents with an immature maxillary central incisor that suffered a luxation injury 18 months ago. The tooth is asymptomatic but shows no response to EPT and a periapical radiolucency is present. What is the MOST appropriate initial management?
- Immediate MTA apexification
- Extraction and implant planning
- Regenerative endodontic procedure (REP) (Correct answer)
- Calcium hydroxide dressing changed every 3 months for 2 years
Correct answer: Regenerative endodontic procedure (REP)
A REP is the preferred first-line treatment for necrotic immature permanent teeth because it offers the possibility of continued root development and wall thickening, improving long-term prognosis over apexification alone.
Question 7: Which of the following is classified as an outcome category for REPs by the AAE as a 'Level 3' or best outcome?
- Resolution of periapical pathology only
- Increased root length OR wall thickness but not both
- Increased root length AND wall thickness AND positive response to pulp testing (Correct answer)
- Canal calcification with no periapical lesion
Correct answer: Increased root length AND wall thickness AND positive response to pulp testing
Level 3 (the highest REP outcome) requires resolution of signs/symptoms, continued root development (length and wall thickness), AND positive response to sensibility testing, indicating functional pulp-like tissue.
ABE Regenerative Endodontics 2
Stem cells of the apical papilla (SCAP) are considered the PRIMARY source of cells for root development during regenerative endodontic procedures.
Where do SCAP reside?