Dentists are urging the federal government to introduce a sugar tax after the latest oral health survey found the rates of both diseases had increased since 2018.

Mikaela Chinotti from the Australian Dental Association also wants clearer food labelling.

"These conditions are largely preventable, yet they've increased in prevalence and we continue to get further away from our goal of improving Australia's overall oral health," Dr Chinotti said.

She wants Australians to be more sugar savvy when choosing their foods.

Nearly a third of adults had untreated and potentially painful tooth decay in 2020, the survey found, up from a quarter of adults in 2018.

More than a quarter of adults had periodontal pockets, a type of gum disease, up from 19.8 per cent.

Just over half of respondents brush their teeth twice a day.

However, less than half had seen a dentist in the past year.

Still, Australians are keeping their teeth longer while oral cancer rates remain static, the survey found.

Australian Associated Press