**Core Concept:** In endodontic treatment, EDTA and NaOCl are essential irrigants used for root canal disinfection and shaping. EDTA is a chelating agent that removes calcium salts and smoothens the canal walls, while NaOCl is a strong antimicrobial agent that cleans and disinfects the canal. The correct sequence ensures optimal effectiveness of both irrigants.

**Why the Correct Answer is Right:** The correct sequence of using EDTA and NaOCl is as follows:
1. Irrigate the root canal with normal saline (Option A) to remove the smear layer, debris, and blood from the canal walls.
2. Apply EDTA (Option D) as it is a chelating agent that removes calcium salts and smoothens the canal walls, preparing it for NaOCl.
3. Irrigate the canal with NaOCl (Option B) as a strong antimicrobial agent that cleans, disinfects, and kills bacteria present in the canal.

**Why Each Wrong Option is Incorrect:**

A. Irrigating with NaOCl first (Option C) may not effectively remove the smear layer and debris, as NaOCl is not a chelating agent.
B. Irrigating with normal saline first (Option A) does not remove the smear layer effectively and does not prepare the canal walls for EDTA.

**Clinical Pearl:** Following the correct sequence of using EDTA and NaOCl ensures optimal cleaning, disinfection, and shaping of the root canal, ultimately improving treatment outcomes and reducing the risk of endodontic failures.