Boyfriend/ Plaque. Tell your boyfriend you are not going to kiss him until he starts brushing his teeth regularly. You can also buy a kids mouth wash that has a dye in it that will show him all the plaque on his teeth when he uses it. Tell him if he does not brush his teeth you will get a new boyfriend who does.
Teeth Hygiene. Tell him you are going to the dentist for teeth cleaning and invite him to do the same.