Participation rates have been in long term decline since changes to registration rules in 2007, when 99 per cent of the 2.5m patients who were registered had contact with their dentist.
The data also shows children and adults from the most deprived areas were less likely to have seen their dentist within the last two years than those from the least deprived areas.
With oral cancer on the rise the BDA Scotland has called for the Scottish government to do more to boost participation among adults in deprived areas. The European age-standardised oral cancer incidence rates for both men and women are significantly higher in Scotland, at 16.8 per 100,000 compared with 12.4 in England, and 11.9 in Northern Ireland.
Robert Donald, chair of the BDA's Scottish Dental Practice Committee, said: "The Scottish government must stop boasting about ‘record breaking’ registration rates. The facts are nearly two million Scots are not getting the NHS dental treatment they are entitled to.
“Scotland can take pride in what it’s achieved when it comes to fighting decay among children. Now, ministers must show some of the same determination to get adults, particularly those from deprived communities, to attend.
“Our oral cancer is on the rise and early detection is key. It’s not enough to get high risk adults on our books or on some government spreadsheet. We need real support to get these patients in our chairs.”