How to tell someone something embarrassing

I'm noticing a really gross habit from my SO. He hasn't brushed his teeth in awhile. He gets sensitive and offended if I hand him his toothbrush.. but he hasn't brushed in longer than I'd like to say. We have a daughter.. this isn't something I'd leave over but it's getting out of hand. I know I have to talk with him about it but have no idea how to bring it up without hurting his feelings. Any advice? I see his teeth getting worse as each day passes. I can't even kiss him. He was abused as a child and one of his parents is dead and the other might as well me since she isn't around and hasn't been since he was a preteen. So I know dental hygiene wasn't important. But it is to me. We also don't have dental insurance so not much we can do there. He says he's never been..