A Dandelion root is quite long
I have used dandelion pullers and if you are lucky, you may get 4-5 inches of roots removed.
But often the dandelion will grow back
And no wonder- here is a rather skimpy dandelion that pulled out easily in some soft garden soil.
See our blog post on dandelion roots
To rid your lawn of Dandelions- see Turf King's lawn care programs with weed treatments using Fiesta iron products.