More than 30,000 Australian children aged five to 14 will be examined over the next four years to determine the extent and causes of tooth decay.

In the first investigation of such size for a decade, the University of Adelaide will also follow up on 15,000 teenagers and young adults who took part in the previous study conducted between 2012 and 2014.

The project is being led by Lisa Jamieson, director of the Australian Research Centre for Population Oral Health, which is part of the Adelaide Dental School.

"With the use of oral examinations and questionnaire data, we will be able to put the results side by side against what was found in the most recent study," Professor Jamieson said.

"We will be able to test, model, evaluate and disseminate evidence that will enable important questions around child oral health, social and emotional wellbeing, school performance and economic productivity to be answered.

"This is incredibly important so that we can understand how deep and widespread tooth decay is, and what actions policymakers can take to ensure children and parents have the right support available to them."

The study is supported by the South Australian Dental Service and the Australian Dental Association, along with health authorities in NSW, Queensland, WA, Tasmania, the NT and ACT.

In the previous investigation, 24,664 children from 841 participating schools took part.

It found about 25 per cent of those aged six to 14 had experienced decay in their permanent teeth, with more than 10 per cent having untreated problems.

Prof Jamieson said it was important to know what the situation was now with the annual cost of dental decay estimated at $1 billion.

"It also has a direct correlation to poor school performance, inadequate nutrition, problems with sleeping and adverse social wellbeing," she said.

The new study is being supported through a $1.5 million grant from the National Health and Medical Research Council Partnership Project scheme.