Information about NHS dental care is "confusing and inaccurate", a consumer watchdog has found.
Healthwatch England said some are travelling up to 40 miles for free treatment, while others end up paying for private treatment after a fruitless search.
The watchdog also warned that some NHS dentists are performing more basic treatments over more complicated, but potentially more beneficial, procedures, such as tooth extractions rather than fillings.
The situation is "simply not acceptable", the national organisation's chairwoman, Anna Bradley, said.
However, NHS England's chief dental officer, Dr Barry Cockcroft, said 93% of people who tried to get a health service dental appointment in the last two years were successful.