The Fawlty Towers star told Hello magazine that reports claiming that he works hard to look good are "nonsense".
Cleese said: "When you get to my age, you do running repairs. I had my fourth hair transplant as it means I don't have to wear wigs in a movie - I hate wigs.
"My teeth were terrible - I had a remodelling of my mouth about two years ago."
He added that he had all the work done before he began his relationship with comedienne Barbie Orr.
The Monty Python actor claimed that the pair dated six or seven times, but he decided two months ago that they should "just be friends".
Orr recently used her personal website to hit back at reports that she lied about her age, joking that she is in fact 73 years old.