As you may know Lemons are highly acidic until digested, at which time they become amazingly alkaline. Some worry about this acidity taking the enamel off of their teeth. In the literature I have read it states to simply wash your mouth out with water (do a couple of swishes) after you drink.
Another precaution you may want to take is to brush your teeth morning and night with ProNamel (a toothpaste by the makers of Sensodyne). It promotes healthy tooth enamel. Research suggests to not brush your teeth immediately after eating lemons, but wait an hour or so. This is because the abrasive ingredients in toothpaste and your toothbrush can further damage enamel. You may also want to try your drink with a straw.