You could further restrict the search to only words that contain those and only those letters. Thats a fairly quick regex with a character class and you've significantly reduced your word sets. MySQL (if you have your database in that) will even let you use regex in a query although i don't know if that will be faster or slower than doing them on your end.

I had a program once that took a set of rules and found all words that matched them, it could normaly be done in a single SQL statment but adding a temporary table saved a lot of time and shoehorning. :)

What is your source of words?