When I write my treatments out I normally don't use dialogue unless something comes to mind and I don't want to forget it. I concentrate mainly on getting my story out, making sure my story is going somewhere, that it makes sense, that the scenes move forward, and my turning points are clear. Later when I do my index cards, (a layout of all my scenes), I might add a few lines of dialogue here or there.
My treatment are about 6 pages long.
One page for the opening and the "hook".
One page describing the action of Act 1
One page for the first turning point.
One page for the actions leading to the middle point.
One page for the actions leading to the second turning point.
One page for the ending.
But everyone has a different way of doing it. I try to limit myself otherwise I'd probally end up with more pages than my script.
If I do add dialogue to my treatment, I just write it. It's not in any particular form.
For EX:
Karen comes home from work and enters the kitchen. "What the heck is this mess?" She walks over to the table. Blah, Blah, Blah.
Remember no one is going to see the treatment but you. Do what ever is comfortable for you.
Steph