When I place the ionic css call the scroll stops running

Hello people!
I’m a beginner with Ionic 2 and I have the following problem.
I took the scrool example from Ionic 2, added it in my application for scroll testing and it works perfectly. But if I instantiate in html the ionic css call it locks the scroll.

Anyone know what I can do?
Note:
I use only ionic.min.css and ionic.bundle.js

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