So just recently I was starting to get fairly good recall (2-3 full dreams per night from a DJ) and was met by an unpleasant surprise last week when I completely stopped being able to rember anything. I have kept writing down as much as possible in my DJ, but simply cannot remember anything. Well, I know what happened. The same night that I lost my recall, I got my braces off and a retainer, which is mildly uncomfortable. I can sleep perfectly fine, but I can’t remember anything… Could anyone provide some help on this subject? 
It could be completely coincidental that you got a retainer when you stopped remembering your dreams. If you believe that you’re retainer is a hinderance to dream recall then it will be. Whether the retainers are the cause or not your teeth will become more aligned to the retainer over time, and they will stop being a problem.
Sometimes I meditate in the morning and I remember my dreams then, but what has always worked best for me is to lie still when I wake up and try to follow my thoughts backward to my dreams. You could try giving yourself a small reward for remembered dreams too, good luck!