Risky drinking and smoking also play a part.
The report, Australia’s Oral Health Tracker, shows the problem starts early with three out of four children and young people consuming too much sugar.
By adulthood, 90% of Australians have experienced decay in their permanent teeth.
Dr Hugo Sachs, federal president of the Australian Dental Association which co-authored the report with Australian Health Policy Collaboration (AHPC) at Victoria University, said one-third of Australia’s five to six year-olds have had decay in their baby teeth.
“This is an unacceptably high rate and puts these children at risk of poor oral health in their development and adult years,” he said.
Too much sugar, regular drinking and smoking not only affects oral health, but is also linked to preventable chronic diseases such as diabetes, obesity and heart disease.
The report also highlights the heavy cost of poor oral health to both the individual and the community.
AHPC director Professor Rosemary Calder revealed that in 2015-16, there were 67,266 potentially preventable hospitalisations for oral health problems. Almost one third were children under the age of nine years.
“Worryingly, there’s a growing number of children in this age group who are being admitted to hospital for dental health reasons,” said Professor Calder.
“Preventable hospital admissions are of concern to all governments. One in ten preventable admissions are due to dental conditions, mostly untreated tooth decay.”
Dr Sachs described poor oral health in childhood as a predictor of disease in adulthood.
“Australia needs to recognise that oral health care is part of good health care, and that access to dental care is a significant contributor to good oral and physical health,” he said.
Professor Calder called for governments to address the underlying risk factors for chronic disease as part of their prevention agenda.
“Australians deserve a healthier future,” she said.