Dear Maha
Please don't worry,but by all means you have to check with the dentist, because sometimes this discoloration is normal and is like having a bruise when you get hit and other times it is a result of the break of the tooth from the inside and no body will know except the dentist.
Usually before any visit to the dentist ( whether when my son had a decayed tooth or just for cleaning ) an antibiotic is given to him.
Once i had to make frequent visits ( 3 visits ) to the dentist for 10 days (tooth decay). in all the 10 days my son had an antibiotic. But one i do just the cleaning which is done only in one visit no more, he takes one big dose of antibiotic two hours before he sees the dentist and no more.
Usually no dentist is familiar with thal but the usage of the antibiotic will prevent any bacteria from entering the circulation. You can also let the dentist have a phone call with your hematologist if he needs to ask about any thing
Please keep us updated
manal