Luckily I work up front so I didn't have to look into it's mouth like my pops (the dentist) and the assistant (only human other than me and dad in the office, bless her soul).  I don't know how either one of them (or YOU, with all due respect) do it. You're right that they don't take care of their teeth.  They are always the ones with major problems.  I guess they gorge and don't brush.  On the rare occasion that I indulge in a soda, I have the sense to brush immediately after, you know, like I learned in grade school.