How do I nicely tell my boyfriend to brush his teeth?

I'm dating a great guy whom I care very much about. The problem is he has a little problem with B.O. and I don't think he brushes his teeth or shaves very often (I don't know because we don't live together and I don't see him everyday). I really don't want to hurt his feelings but I don't know how to put it to him lightly. Any suggestions are appreciated.