Tetsuji Takechi - Hakujitsumu aka Day Dream (1981)

Review from IMDb-
Surreal mixture of pinku, pornography and vampire horror
"Daydream" is a structureless succession of bizarre and erotic set-pieces revolving around a series of fantasies in a dentist's waiting room. A young woman named Chieko begins hallucinating whilst sitting on the dentist's chair. Her hallucinations involve a dental surgeon, who molests and sexually abuses the woman. She is subjected to a lengthy bondage session by the dentist, then she is pursued naked by him through a shopping mall and so on. The uncut Dutch version of "Daydream" contains several explicit scenes of pornography including a very long sequence of Kyoko Aizome being fingered by the dental surgeon. The commercial success of the film resulted in making "Daydream 2" aka "Captured for Sex" in 1987.