Dentosphere : World of Dentistry

# 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

# 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 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: 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.