When you dream of the dentist, then such dream could indicate the actual fear you have for dentists. The dream could also show that you do not trust some person in your waking life. The dentist in dreams could be coming from the internal stimulus such as tooth pain you are suffering from while sleeping, therefore you see a dentist. If you see the dentist that is fixing someone elses teeth, then it means you will be surprised by other peoples negative experiences.
Read more about dreaming of Dentist in other dream meanings interpretations.