Dentists in England are returning hundreds of millions of pounds a year to the government for unfulfilled NHS care, the BBC has learnt. Over the last two years, more than £900m has been handed back - £1 out of every £7 they have been paid - as dentists instead prioritise private work. The findings help explain why despite record sums being set aside for NHS dentistry, so many patients are struggling to get one - more than a fifth of people report not being able to access care when they need it. The government said improvements were being made this year and any money returned was reinvested into services. Under the NHS contract, dentists agree how much NHS work they are going to provide during the year and receive monthly payments from the health service for that. If a dental practice underdelivers – classed as below 96% of the contract value – the NHS then recoups money from practices the following year.…