My nine year-old has just had a developmental leap with this sort of thing.
I've been brushing his teeth for years because he didn't enjoy it at all, but all of a sudden he's taken to doing it twice a day. He's having showers now instead of baths and is even washing his own hair
It seems he's enamoured by the whole procedure. He showers then hops out and dries himself, then puts the towel on and enjoys standing in front of mirror taking his time to brush his teeth - I bought him an electric one to celebrate.
Last night in bed he remembered that he hadn't brushed and couldn't settle until I let him get up to do it - wonders will never cease!
Adopt the pace of nature; her secret is patience.
Ralph Waldo Emerson