Libgdx change to other screen and dispose current one

I am trying to switch to a GameScreen when the LinearVelocity of a Box2D – Object is x = 0.
If it is so, I am using the setScreen() – Method by calling the main class. This works perfekt, but when the screen should change, it just flickers, which is most likely caused by the render() – method in the screen class.
So my question is now, how to dipose that render method or how to dispose the whole screen class, so that I only the new screen appears!
Thanks