<human>: My boyfriend and I have been dating for four years now. He is generally well kept, he showers every day and dresses well, but his one big hygienic flaw is that he does not brush his teeth regularly. For example, this morning he didn't brush his teeth, and when I suggested he should brush them he used the excuse that he was just going to drink coffee when he got to work so there was no point. 

Whenever we travel or go on vacation together he almost always leaves his toothbrush at home and uses the reasoning that "its a vacation".

I have tried explaining to him many times why he needs to brush his teeth more. Whenever I do he either makes an excuse why he doesn't need to, ignores me, or gets offended. I constantly have to remind him to brush, and it makes me feel like a mom trying to teach a little kid. 

He is a grown man, how can I make him realize that he needs to brush his teeth everyday (preferably at least twice)? I don't want to be his mom, I feel like brushing your teeth is common sense for an adult, I shouldn't have to tell him! 
 

I should also add his parents (as far as I know) have good teeth brushing habits. I even told his mom about his terrible teeth brushing once and she yelled at him, of course to no effect.

Can you condense the text into three sentences or less?
<bot>: Boyfriend makes up excuses why he doesn't need to brush his teeth. It's gross. Nothing I say will make him brush his teeth properly and I feel like a mom for having to nag him about it.