Djembe, a 16-year-old lioness at Wellington Zoo, has undergone a four-hour operation to have a root canal performed on a lower canine.
A team of 20 people were involved in the operation on the 140 kilogram cat.
Vet Sarah Alexander said it was a little more complicated than usual because it was hard to get the material out of the 11-centimetre long tooth before it could be filled.
"She is a dangerous animal and dangerous animals have the potential to cause real havoc during their procedures," Dr Alexander said.
"So if they wake up we can be in a bit of trouble, that's one of the reasons we've got specialist anaesthetists helping us today."
The procedure was carried out by Massey Vet Angus Fechney, who specialises in animal dentistry.
"Luckily Djembe hasn't shown any sign of pain or infection with her tooth, it's just that we noticed there was a little hole on top and that's where the root goes down," Dr Alexander said.
So how do you know when a lion needs a root canal?
"The keepers have the lions amazingly trained. They can actually get them to open their mouths nice and wide and we can check all of their teeth," Dr Alexander said.
But the team was wary of Djembe's (pronounced Jem-by) temperament.
"Djembe is one of our feistier lionesses, so she's generally not overly happy to see us at the vet department. As much as we love her, she doesn't necessarily feel the same about us," Dr Alexander said.
She said there are extra risks because of Djembe's age.
"She is really a geriatric lion. Lions live perhaps into their early 20's in captivity. As they get older we tend to run into age related problems like arthritis, additional teeth problems, kidney-problems etc."
Djembe is one of three lioness sisters in Wellington, which were born at Auckland Zoo.
And it's not just lions that require occasional root canals - Dr Fechney has also performed a root canal on a bear this year.
"We're looking at booking him in for a baboon and an otter, so we're keeping him very busy," Dr Alexander said.
She said the specialists often donate their time and expertise because Wellington Zoo is a conservation organisation.
Djembe was expected be returned to her enclosure under anaesthetic, before being given a reversal drug to wake her up 15 minutes later.