I was brought up (in Leicester, in the forties and fifties) to 'clean' my teeth. I remember there was an advertising slogan for Maclean's toothpaste, 'Have you Macleaned your teeth today?', so it must have been common usage. But nowadays everyone seem to talk of 'brushing' their teeth. Has there been a change (and, if so, why)? Or is it a regional thing?