Currently resin fillings typically last for seven to ten years at most before they crack and fall out.

But now scientists have worked out how to make fillings stay in the teeth for much longer.

The breakthrough was made possible by an extract from the bark of pine tree roots, which scientists discovered alters the chemical structure of teeth to make them stronger and allow fillings to bind to them better.

Dr Guido Pauli, of the University of Illinois at Chicago, said compounds in the pine tree extract work by strengthening dentine - the tissue layer beneath the enamel in teeth.

He said: "The weak link in the chain of bonding is the interface between the resin and the dentine.

"We have clear evidence that our intervention materials change this interface much to the better."

Tests show the tree extracts can increase the strength of dentine by up to ten times.

The misery of repeat trips to the dentist to replace lost fillings could soon be consigned to history.

The results of the study were published in the Journal of Organic Chemistry.