The probe will investigate whether patients are being forced to travel too far to see a dentist, if they require help in the evening or at weekends.
Embarrassingly, it comes less than three months after new out-of-hours arrangements were introduced – from the start of April – when the new Health Act came into force.
Meanwhile, Dentistry has been told of an alarming case which has prompted a Conservative MP in West London to raise fears that care is inadequate.
Angie Bray, MP for Ealing Central and Acton, tabled parliamentary questions after a constituent wrote to her to protest about his out-of-hours treatment.
The unnamed man – in severe pain – went to a hospital A&E department, because there was no help available from any dentist within reach across West London.
Once there, he was examined by a nurse who advised that he needed to see a dentist urgently – and suggested he would have to travel to Oxfordshire.
Mrs Bray said: 'My constituent could not believe that he would have to travel outside London to see someone for an emergency. He was pretty angry.
'He is unemployed, so couldn’t afford to travel to Oxfordshire in any case, and it does seem extraordinary to me, if this is a widespread problem.
“It certainly never occurred to me that out-of-hours care could be so bad. My constituent appears to have identified a quite severe gap in the system.'
In reply to questions tabled by the MP, health minister Dan Poulter said out-of-hours (OOH) dental care in Ealing was 'part of a joint service covering eight boroughs in North West London'.
The minister wrote: 'Calls are forwarded to a dental nurse triage service, which is available from 6pm to 10pm on Monday to Friday and from 9am to 10pm at weekends and on bank holidays.
'NHS England is currently reviewing the OOH dental care system in London, to ensure that capacity is sufficient to meet demand for the service.'
In reply to questions asked by Dentistry, NHS England suggested its 'internal assessment' would take up to nine months to complete.
A spokesman said: 'The aims are to understand the provision landscape across London as a whole and to map the patient pathways.'
Asked if there were fears of a lack of out-of-hours care, the spokesman replied: 'This is currently being assessed, particularly in light of the introduction of 111.'
There has growing criticism of the new 111 service – which replaced NHS Direct across England, in April – and the affect on crowded casualty wards.
Callers have waited up to 30 minutes to get an answer on the 111 line – or abandoned calls altogether – forcing people to go to A&E instead.
Many hospitals have simply dropped the government's four-hour target to deal with patients arriving in casualty, because of soaring demand.
By parliamentary correspondent Rob Merrick