# Calcium hydroxide is advocated as an inter appointment intracanal medication because of

# Calcium hydroxide is advocated as an inter appointment intracanal medication because of:
A. Its ability to dissolve necrotic tissue
B. Its antimicrobial property
C. Its ability to stimulate hard tissue formation
D. Its powerful bleaching effect

The correct  answer is B. Its antimicrobial property. 

Most studies report culture reversals during the interappointment period when active antibacterial dressing is not used in the root-canal system between appointments. The reversals are due to regrowth of residual bacteria or recontamination by bacterial leakage around the access cavity

dressing. 

Classical and well-controlled studies (Sundqvist’s group) evaluated the effect of various root-canal treatment procedures on the microbiota both qualitatively and quantitatively. They tested the effect of mechanical preparation, saline or sodium hypochlorite irrigation (0.5%, 5.0%, 5.0% with EDTA), the addition of ultrasonic activation to the irrigation and calcium hydroxide dressing; each addition to the chemical canal preparation improved the antibacterial effect, reducing residual bacteria further. They found the antibacterial action to reduce the number of bacteria from an initial range of 10^2–10^8 cells to 10^2–10^3 fewer cells after initial debridement, further reducing down to no recoverable cells (from the prepared part of the root-canal system) after interappointment dressing with calcium hydroxide.

Reference: Endodontics, 4th Edition, Kishor Gulabivala, Yuan-Ling Ng, Page no. 83