I don't believe I have dense breasts (at least it was never mentioned). However, I did have a mammogram that showed calcifications and they had me come back and do another which again showed them. I then asked if I should stop taking my calcium supplement a number of days prior to my mammo and they said "yes". On my next mammo, the calcifications were gone.
Breast density is more common in young and thin women. I would think that the density and calcifications warrant follow up testing. Have you had further imaging done? I ended up having a biopsy when I had density, calcifications and oddly shaped calcifications. I did not have cancer (but was scared). For whatever reason, more dense breasts especially when we are older is connected to breast cancer. https://www.mayoclinic.org/tests-procedures/mammogram/in-depth/dense-breast-tissue/art-20123968. And certainly it does make imaging harder to detect things. So, are you following up with anyone? Many women have results that cause a bit of concern and it is just fine. I'm not trying to scare you. But making sure you are prudent in evaluating this further is important.
As women age, breast tissue is expected to get less dense. I don't think this is an absolute rule, though.