A dentist has been faulted for leaving a cotton roll in an elderly patient's mouth and failing to detect it when he came back in pain days later.
A report by Deputy Health and Disability Commissioner Rose Wall said the unnamed dentist breached patient rights after giving an 87-year-old man a filling in August last year.
Ms Wall said the dentist failed to keep a record of how many cotton wool balls he used, which was considered proper practice.
The patient was given antibiotics by his family doctor, before going back to the dentist when the pain didn't go away.
After 11 days, more antibiotics and another doctor's visit, the patient went to another dentist, who found and removed a dental roll tucked underneath his tooth. There was a deep ulcer where it had been sitting.
Ms Wall said it was difficult to say how it occurred and concerning the dentist didn't detect his error.
"It's unclear as to why the dentist did not detect this error, particularly as the second dentist very discovered very rapidly the problem," she said.
"The second dentist rapidly found the cotton ball when he presented, and there was this nasty ulcer in the base of his mouth next to his molar tooth."
The first dentist apologised and gave the patient a refund.