usually you will need to be bulimic for between 1-3 years for coonsiderable enamel erosion to occcur. if there is a small amount it could be put down to acid refulx or poor diet (to much soft drink).
bulimics have a significant pattern that occurs only on the back teeth and wears them down, evenntually forming cavities. there will also be marks on hands, swollen glands andsometimes red marks on cheeks near back teeth for them to spot.
dentist are trained to spot these symptoms and usually will just talk to you about whether you are getting help (up to you if your honest or not)
they are not as concered in your eating disorder as they are in your teeth.
the bests things you can do are to brush teeth BEFORE purging. then drink lots of water between purges and rinse mouth out. you can use baking soda, or tums to neturalise acid after purging but do not brush as this can push acid into gums and cause futher damage.
the best option for healthy teeth is to seek help, wether medically, or counselling or just confiding in someone.
from clare (bulimic for 5 years now in recovery)