I'd recommend using the cheat described on the top of the page to unlock all levels if you are having trouble.
I didn't make the bars at all clear in their purpose, but one is anger, and the other is teeth cleanliness. The cleanliness bar is 50% the bottom row and 50% the top row. Touching his gums or eyes will increase the anger meter, and he'll eat your toothbrush if you do it too much. You have 2 spare toothbrushes. Its probable that you got one to like 99% cleanliness or something
(its also a crappy unfinished demo, sorry)