<prompt> What is the advantage of crown down technique:Zipping is less.Working length is less likely to change.Better penetration of irrigants.All of the above.  <response>: Crown-down techniquestep back telescoping technique: Coronal 23rd preparation with 15, 20, 25 H file GG drill to flare. Apical segment preparation with 10, 15 no. file coronal segment. Advantages: ZIPPING is less, working length less likely to change, better penetration of irrigant. 