I have a dental phobia, too, but it is much less of a problem than it was for many years. I also have some other phobias. When my T and I did systematic desensitization, before we ever did any visualizations, she told me to make a list of all the "parts" of the phobia, going from least afraid to most afraid, and we would work from that list. She also did EMDR with me, and that helped a lot.