Only a couple times. The most memorable was when I had a molar extracted by 2 very attractive dental students. They gave me enough novacain to numb an elephant so I didn't worry about any pain. When it came time to actually pull, the first one leaned over me from above, resting her full, round D-cups on my forehead and giving me a wonderful view down her blouse, watching her curvaceous body twisting and turninng back and forth, trying to find just the right position for the best leverage.
After several minutes, the first students' hands tired out and she called over the second, equally attractive, student. The second student tried the same position, giving me another wonderful view, but her long hair kept falling down in her way. She moved around the chair and came up from below. Resting one knee on the chair between my legs, she straddled the armrest - placing my hand in a very happy position - and had the first student hold her hair back as she leaned over in front of me. My, what beautiful black hair and green eyes she had! She tried for several minutes before she also began to tire.
Just then, one of the regular doctors came by and asked if everything was alright. Winded, both of the students asked for his help. He took all of a minute to go rock, rock, rock, pull, and remove the tooth. Before he left, he patted my hand, apologized for the difficulties, smiled, and told me "We know that going to the dentist is never fun, but we try to make your visit as enjoyable as possible."