The head injury could have caussed but
I am not a doctor so I cannot diagnose. If you are worried about brain injury consequences, then please see your GP.
I find wearing an earplug in one ear (the one that you're not using to listen to whoever you're talking to) helps to filter out some of the noise.
You can buy noise-cancelling headphones in big electronics stores (I live in London so I went to Tottenham Court Road), or on the internet. Get the one with the highest percentage noise blocking. Mine block 85.4% of all incoming noise. Very useful when travelling on the Underground.
As for your teeth, I have the same problem. I posted in
http://www.recoveryourlife.com/forum...d.php?t=163666 and there are some quite good suggestions.