It depends on the actor, but generally yes. It is physically impossible to kiss without your tongue touching your partner's.
It might not be the whole tongue and it might not be there for more than a fraction of a second, but if the actors are doing an "erotic" scene, their tongues will definitely make contact and the actresses will definitely get a mouthful of spit.
Actors kiss in front of the camera for a movie or a play for a lot of people to enjoy that hot smooch. Actors are not just going through the motions, but they are making the kiss look real. When an actor is kissing someone, he does not use his tongue. In a scene, there must be a reason to kiss.
For instance, if you are kissing someone as a form of saying goodbye, you might use your tongue. If you are kissing someone as a form of tenderness, then you do not use your tongue. When you do not use your tongue, you can get a better feel for the person you are kissing.
Actors do this for a few reasons:
1. They don't like being sticky.
2. They are paid to do so.
3. They don't want to be called a "s-x" in the tabloids.
4. They want to go home with the girl they are making out with.
