I don't know too much about this....but I do remember our specialist saying that my daughter's lip hemangioma might sort of "flare up" when she cuts a new tooth. I did notice extra redness at times but nothing extraordinary. Hers didn't really go into her gums very much though. She started getting teeth at around 4 months of age so her hemangioma was still in its growth phase (although she was on steroids so that kept it under control.) You have a good question...I'm sure it would be helpful to have a dentist who is knowledgeable about hemangiomas.