"It's rather gruesome, yellowy, browny with a cavity."
Dot has previously sold other items related to the late singer - who was shot dead aged 40 in 1980 - including a jacket he wore on the cover of the Beatles' 1965 Rubber Soul album.
Her son Barry Jarlett explained: "John was in the kitchen and he had this tooth which he had wrapped in a piece of paper.
"He said, 'Dot will help you dispose of this,' and then he said, 'Or, as your daughter's a Beatles fan, you can give to her as a souvenir.'
"It is something that we felt was very personal and my mum actually gave it to my sister who has kept it safe."
Earlier this year, a lock of pop star Justin Bieber's hair went under the hammer for £25,000 (NZ$50,000), with all the proceeds going to charity, and a jar of Angelina Jolie's breath once sold for £330 (NZ$665).
- BANG! Showbiz