Dr. What causes your gums to bleed pretty heavy, during a crown prep. I have healthy gums and my doctor says I have no medical problems that should have caused this . Also to mention within a 24 hour period, I went to the dentist he prepped me for a root canal. I went that say day and had my root canal done with no infection and know problems . I went back to the dentist the following morning as he requested, to put my temporary crowns on . The dentist was drilling around alot and my gums started to bleed and he ask me was I taking any aspirin.. What would have caused the bleeding? I dont take aspirin. I take synthroid and he is aware off that, and I take no other meds and none prior to going in . Thanks for your advise It would be appreciated.