You probably know more about your own people than I do, I wasn't really expecting anyone to reply by saying that any of the stereotypes raised were true! My uncle was Irish and he was completely wankered every time I ever met him, I was mid-rant at the time and might have forgotten that.
Also, I think whoever started this ridiculous thread was thinking more about tooth decay than just having crooked teeth like your wife. Living in upper-lower-middle-class Warwickshire I can honestly say that I don't know anyone with major tooth decay. I beleive that the majority of British people are fairly consciencious about their teeth.
While it is true that the council-estate dwelling, beer-swilling, doll-queueing, happy-slapping, street-talking, social-services-tormenting underclass that Britain has developed in recent years probably have generally quite poor personal hygene standards, It is good to remember that they ae not representtive of the whole of Britain, a fact that even I forget sometimes.