13. Which one of the following is apical to coronal technique of root canal a. Step down b. Step back c. Crown down d. Modified double flared e. Balance forced

The correct answer is c. Crown down. The apical to coronal technique of root canal preparation involves removing the coronal portion of the tooth structure while maintaining or creating a coronal seal. The 'crown down' approach is commonly used in this technique the coronal portion is removed gradually, and the apical portion is cleaned and shaped first. This technique allows for better control and visualization of the canal, especially in cases where the coronal portion may be compromised or difficult to access.