Who knew! Taking care of your gums as well as your teeth is important to your overall health, not just staying away from dentures as long as possible. Besides improving your health, brushing your teeth and gums well can make for shorter, less painful trips to the dentist.
In come the electric toothbrushes to the rescue! We have a Sonicare Elite, available for $89.99 from drugstore.com and thanks to the built-in timing function, we brush our teeth for the full two minutes dentists recommend (seriously: try timing yourself sometime if you don't use a brush with a timer built in).
It took us a bit of encouragement from our dentist to plunk down the $100 for one of these, but the clean feeling we get every day after brushing can't be compared to a regular toothbrush. Consider it an investment in your health for the long-term: there's a 
i have always wanted to switch to an electric toothbrush, and had one before braces like 9 or 10 years ago. i still have that stupid permanent retainer behind my bottom front teeth - which doesn't even do it's job because all my teeth have shifted and are completely uncentered - but the dentist won't take it off and i question whether or not an electric would clean around under behind, what have you, than a regular toothbrush. hmm.
elizabeth: I have one of retainers myself, though it's done it's job and my teeth haven't moved. It definitely makes cleaning easier/better around and under it.
I have an old retainer that's been in my mouth for about 13 years now, so it's much bigger than the ones they have now...my dentist sent me to an orthodontist to see about getting a smaller one put on, and the orthodontist said my retainer and teeth are in the best condition he's ever seen for the amount of time I've had mine. He said that unless I really wanted the new one (which I'd have to pay for out of pocket), he recommended I keep mine.
I'm sure this is because of the Sonicare because I'm not good about flossing my retainer, it's such a pain.
I have an older (standard) Sonicare; it is fantastic. My dentist recommended it and it is worth every cent.
sonicare blows every other electric toothbrush out there away. it's just incredible.
I have the battery powered one. Cost less than $40 and I only have to replace the batteries about once a month. My teeth have never been cleaner.