Karla Selley was being brought round from the anaesthetic at Towngate dental practice in Leyland, Lancashire, when she developed breathing problems. She was taken to Chorley Hospital on Monday afternoon but doctors could not revive her.
Karla, from Leyland, needed the tooth removed after an abscess had flared up. She had one tooth removed before she went on a family holiday to Cyprus but the second extraction had been postponed until her return because she had become frightened when she saw the needle.
Stephen Armstrong, 28, the partner of Karla's mother, Tracey, 30, said: "She saw the needle for the second time before we went away. The dentist said, `There's no way she's going to let me use that' and an appointment was arranged to use gas ... Tracey took her in and she went to sleep and that's all we know - she didn't wake up. It's just devastating."
Police said they would be interviewing members of the dental practice.