Well you see..
Osu represents the fact that you are a virgin, for that everyone who plays osu is incapable of talking to a woman (unless if you are a gamer girl, which doesn't exist). This stereotype is believed to be true among the community because we worship our 2D anime waifu and refuse to communicate to the outside world via irl conversation. In this case, it is telling you that before this, you are a weeb who neglect real life to immerse yourself into this downward spiral called otaku culture. This becomes more meaningful as the dream proceeds and we can see teeth. These teeth stands for you refusing to leave this unhealthy lifestyle, as these teeth are planted deep in the pulp, just like the weeb culture attraction has digged deep inside you. This metaphor is warning you the seriousness of this problem and how terrible it has become. Having your teeth falling out means that you are finally willing to leave this bad habit behind and embrace a new healthy lifestyle that enables you to function like a normal human being. You are now able to communicate with other people, especially women. Talking about falling teeth, last weekend I had myself a medium rare steak. It took me a whole minute to finish chewing a small piece of it, and I didn't even finish chewing that piece of steak because I gave up half way since I felt like my teeth were going to felt off and swallowed it. I almost choked too because of how chewy the thing is. I swore to myself from that day on that I would never eat medium rare steak ever again and would only eat rare steak. You know who else almost choked to death too? Pablo Picasso. Actually he did die because of choking. There's an old Catalan proverb that says "The table kills more people than war does" - and it is truly applicable for this situation as Pablo died from eating too much food and choking. Therefore, food is bad and we shouldn't eat them at all.