People could be paying too much for dental treatment because dentists are not being clear about their prices, consumer champion Which? has found.
A survey of 1,000 people in England found one in five was overcharged for treatment while 50% said no price list for treatment was displayed.
Which? said dentists should be "upfront with patients about costs".
The Department of Health said dentists were contractually required to display up-to-date charges.
The people surveyed had all been to see their dentist in the past six months.
While 80% said they trusted their dentist's advice on treatment, around 40% said they were not clear about what treatment they were entitled to on the NHS.
Patients should only be asked to pay one charge for a course of NHS treatment, even if that means several visits to the dentist.
Yet 19% of NHS patients said they paid more than once for the same course of NHS treatment.
http://www.bbc.co.uk/news/health-30852261
There was also evidence of confusion about how NHS and private treatments differ