Dementors

[agdisney]

No: HPFGUIDX 146793

Andie:
I was wondering if JKR ever mentioned how Snape would deal with 
dementors.  In POA Harry drives the dementors away before Snape
arrives & takes him & Sirius to the castle.
In HBP Harry is working on an essay for Snape on the best way to
tackle dementors but he knows that he will receive a low mark
because he didn't agree with Snape's way of doing it. pg 448 US.

Is there a difference in how a Dark wizard communicates with dementors?