Not being recognized is distressing for dementia family members. It happens at different stages (especially by mid-severe stage); it may never happen to you at all. But if it does, it helps to be prepared.
Try to dwell less on whether your name is known and used correctly and more on the underlying emotional truth. Does the person seem to recognize your presence as a friendly one? Do you get a smile or sense of calm from him or her?
Avoid the temptation to check in with a test: "Hi, Mom! Do you know who this is?" Or, "Bob! Remember me?" Compare that with the warmer setup you provide by saying, "Hi, Mom, it's your oldest daughter Anna, come to see you again. I'm so happy to see you because I sure love you."
Don't stress, though, if things reach the point where you get no response at all. Whether or not you can discern a different response between the two examples above, the first approach creates stress and anxiety in the person with dementia, as if he or she were being tested. The latter response telegraphs affection and warmth, a much better starting place -- even if it's not fully understood.