Root canal: the phrase is enough to make grown men cry. To make it worse, it's not an operation that dentists particularly enjoy doing.
Now a specialist company, Smartseal, has developed a novel way of filling dental cavities, using a thin length of plastic that expands on contact with moisture. It is inserted into the freshly drilled cavity and - because it is hydrophilic - swells to fill the hole. A special paste then seals the cavity, like dental amalgam.
The new product relies on materials technology and micro-injection moulding. "It has taken eight years to develop, including research, material testing and product testing," says Jerry Watson, chief executive of Smartseal.
Dentists have traditionally filled a root canal cavity with a tiny slug of hot gutta percha (thermoplastic natural rubber), which has a tendency to shrink on cooling. This can leave voids in the cavity, leading to possible re-infection and further decay. Paul Holden, Smartseal's operations director, says: "Gutta percha has been in use in root canals since the 1850s, despite concerns related to potential latex allergies and thermal cell damage from thermal condensation."