The Health and Disability Commission of the country on Friday last released a report on the case of the 81-year-old man, who never fully recovered his previous good health following the incident. He died within a couple of years.
The commission said the man entered a private hospital for elective back surgery in February 2005.
The commission found the denture was undetected for so long because of neurological impairment, caused by a cyst in the centre of the man's spinal cord. The fluid-filled sac pushed on his brainstem, damaging the parts responsible for swallowing and the feeling in the back of his mouth.
The man's upper denture, which doctors noticed was loose, was taken out before the surgery.
But somehow, the false teeth managed to get back into the man's mouth, though no one admitted to putting them there and, according to a nurse, there was "no way" the heavily sedated man could have put them back himself.
After the operation, the patient told his carers he was in "extreme pain", and was given painkillers.
Under 24-hour supervision, nurses noticed the elderly man was "very chesty", spoke with a particularly husky voice, and couldn't eat more than a couple of spoonfuls of milky porridge at a time.
On the second day after the man's operation, doctors recorded his voice was down to a whisper, and ordered chest X-rays. They found evidence of congestive heart failure.
That afternoon, the man was moved into his own room after suffering coughing fits.
Three days later, the man's condition deteriorated. He continued coughing, his oxygen saturation level plummeted, and while he was being washed, the 81-year-old stopped breathing completely.
Doctors put a laryngoscope down the man's throat, finding his missing denture.
They removed the teeth, resuscitated him and transferred him to a public hospital. He never fully recovered, and died within a couple of years from respiratory illness.
Experts looking at the case said a serious underlying neurological condition allowed him to cope with having his teeth down his throat.
The commission found the doctors took all due care during the surgery.
However, it recommended the anaesthetist apologise to the man's family and review his practice for leaving the recovery room for a time and because of the ventilator he used.
The names of all those involved were withheld by the commission.