My mother, age 92, had a dental deep cleaning on the left side of her face. Afterwards, her face was black-and-blue and swollen on that side, which has persisted for more than a week. Is this normal or indicative of a problem in the way the hygienist did the anesthesia injection or the cleaning. My mom is returning to do the right side, so I want to consider having it done by a different hygienist.