Does an unopened box of individually sealed green tea bags contain
more antioxidants than an unopened box of unsealed greentea bags ? If
so by how much ?

Maybe a tiny amount?  The unwrapped tea would oxidize slightly,
becoming more like black tea?  But I imagine the difference is very
small.  Drink whichever you enjoy more, and any extra that you consume
would probably make up the difference.

This is my favorite so far.  It's excellent as iced tea:
http://www.liptont.com/our_products/green/lemon_ginseng.asp

May your future be flavonoid-filled.