Hydroxyapatite comes in different forms. Radiesse is round particles of calcium hydroxyapatite (a natural mineral bone like material normally present in the body) floating in a gel. Because of its simple chemical mineral structure it is non-allergenic so no skin tests are needed and because of the particle size it can last 2 or more years after injection. It is most commonly injected to reduce skin wrinkles or folds of aging.
Hydroxyapatite is also available in paste and solid implant forms without gel for augmentation of bone. Unlike solid hydroxyapatite implants the paste is non-porous so bone and soft-tissue ingrowth does not occur. Over time the solid implant is partially absorbed and replaced by bone but it never goes away
If your doctor used the paste form it will be easier to remove than the solid form. The solid form has bone growth into over time making it harder to remove but it should still be doable with greater effort. If there is bone ingrowth it may have to be removed in the hospital using a burr because most office ambulatory surgery centers do not have the requisite bone removing equipment.