Endodontic retreatment

# Endodontic retreatment:
A. Is as technically challenging as original treatment
B. Has a poorer prognosis than original treatment
C. Is performed only on endodontic failures
D. Has different objectives than primary treatment

The correct answer is B. has a poorer prognosis than the original treatment

Post and Core in Endodontics

# In restoring an endodontically treated tooth for post core, an absolute minimum of apical fill of gutta percha to be left over to prevent leakage is:
A. 1 mm
B. 2 mm
C. 3 mm
D. 4 mm

The correct answer is D. 4mm

Since there is greater leakage when only 2-3 mm of Gutta-percha is present, 4-5 mm should be retained apically to ensure an adequate seal. Although studies indicate that 4 mm produce an adequate seal, stopping precisely at 4 mm is difficult, and radiographic angulation errors could lead to retention of less than 4 mm. Therefore, 5 mm of gutta-percha should be retained apically. 

Concentration of EDTA used during BMP:

# Concentration of EDTA used during biomechanical preparation (BMP) is:
A. 20% at pH 7.4
B. 15% at pH 5.0
C. 15% at pH 7.3
D. 25% at pH 7.4

The correct answer is C. 15% at pH 7.3

EDTA has a property of chelate formation with calcium salts. Disodium salt of EDTA is used in endodontic therapy for dissolving pulp stones. 

Length of a Peeso reamer is:

# Length of a Peeso reamer is:
A. 28-32 mm
B. 30-35 mm
C. 35-40 mm
D. 40-45 mm

The correct answer is A. 28-32 mm

- Standard Peeso reamer is of 32 mm length.

- Short Peeso reamer is of 28 mm length.