A dentist faces possible legal action after failing to tell a patient he had left a piece of an instrument in the root of a tooth.
The case is detailed in a decision released on Monday by Deputy Health and Disability Commissioner Theo Baker.
The unnamed dentist carried out a root canal procedure on an 18-year-old in 2008, but didn't tell him that during treatment one of the fine instruments used had broken and remained in the root canal.
Two years later, with the man complaining of a dull pain, the dentist retreated the tooth to remove the part, again without saying why the extra work was needed and damaging the root in the process.
When his tooth broke away, the man saw another dentist and was told about the instrument.
Ms Baker says the first dentist breached patient rights by failing to tell the man what had happened and by failing to keep proper records.
