Thankfully, that whole 'teeth' comment went right over Bart's head--either because he was distracted or because a lot of things went over Bart's head. This was one that, had he actually put 2 and 2 together, he would have been grateful it went over his head in the first place.
"I don't know. Maybe not mad. She wasn't like, 'let's break up' or anything. I just..." He shrugged, staring at his gigantic feet, "I haven't talked to her in a couple days." The guilty expression on his face said that Bart was more than aware that that was a problem in and of itself.