Monmouth MP David Davies said mandatory teeth checks would reassure people that the unaccompanied migrants coming into the UK to join relatives were indeed children.
"If they are jumping on lorries, they are not going to be averse to lying about their ages. We should do the tests," Davies said.
Downing Street said "a whole range of checks are in place that the Home Office and Border Force are using in cooperation with partners" and theUK Home Office was forced to issue a statement against dental checks.
"Where credible and clear documentary evidence of age is not available, criteria including physical appearance and demeanour are used as part of the interview process to assess age," the spokesperson added.
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The first children with links to Britain arrived this week, after French authorities ratified a list drawn up by the charity Citizens UK, which is working with the UK government to bring unaccompanied minors over from Calais in France.
However, photographs of some of the children have been printed on the front pages of some UK newspapers alongside headlines questioning their ages.
"It's not only an inaccurate method for assessing age, but it is both inappropriate and unethical to take radiographs of people when there is no health benefit for them," a BDA spokesperson said.
Diane Abbott, Opposition Labour's shadow home secretary, said it was "an outrageous demand, which would further violate the human rights of vulnerable refugees".
"They have suffered insanitary and dangerous conditions and should have been admitted long ago. This is a vile, reactionary clamour. It distracts from the government's responsibilities to these refugees, which it has largely neglected to date," she said.
UK officials in Calais have been focusing initially on unaccompanied minors who have the right to join relatives in the UK under EU legislation, known as the Dublin regulation.