I think you'll need to explain that better. I've read it 3 times and I'm still not sure what you mean.
You can make all posts need approval. You'll have to recruit a lot of mods to keep up and it'll annoy the heck out of your users.
You can make just new topics needs approval with this extension
https://www.phpbb.com/customise/db/exte ... _approval/
Are you trying to prevent something? Spam?