Visiting the dentist, especially to have a tooth filled, is nobody's idea of fun. So suffering the added pain of a return visit for a cracked or loose filling just feels like insult added to injury. A new high-tech method of analyzing the way in which a tooth repair sets developed by British scientists might reveal a way of keeping those extra trips back to the dreaded chair to a minimum.
Dental glass cement — invented in the U.K. — is made from glass powder, a liquid polymer and water. According to the United Nations, it is the "preferred non-toxic choice to mercury amalgam," which has been the first word in fillings for almost 200 years. Dental glass has several advantages over its predecessor. Apart from being mercury-free and having a shade and texture that matches real teeth, its chemical formula means it (theoretically, at least) creates a much better bond with tooth enamel, sealing up the insides and preventing further decay.
Scientists at Queen Mary University of London (QMUL) and Aberystwyth University in Wales have located the "sweet points" of dental fillings — those times when the cement used to fill cracks regains its elasticity before it permanently hardens. This research — which appears in the journal Nature Communications — could allow science to fine tune the process and, the team says, could soon mean more durable and longer-lasting fillings. With a reported 92 percent of American adults between 20 and 64 having dental caries in their permanent teeth, this has to be something to smile about.
Using "nano-level dentistry," the team was able to take a microscopically close-up look and measure how the dental cement sets in real-time. They used computer models to aim intense beams of neutrons at their target, enabling them to observe the surface between the hard glass particles and surrounding polymer and to watch as the strength of the cement progressed. They discovered that, rather than being a smooth and continuous, the way dental cement sets is actually an uneven, stop-start process.
The "sweet points" the scientists identified are moments in the first 12 hours of setting when the cement starts to approach the toughness of tooth enamel. "Dental fillings are really complex materials," says professor Neville Greaves from Aberystwyth University, co-author of the study. "Using neutrons we have discovered how mechanical toughness develops, element by element. This is fundamental physics in action for the general good."
"Most of us have fillings in our teeth and know that a crack means a trip to the dentist for a replacement," says Greaves' co-author, Dr Gregory Chass from QMUL's School of Biological and Chemical Sciences. "Our works opens up the possibility of tailoring the strength of non-mercury cements by homing in on the special setting points — which we call "sweet points" — to make environmentally-friendly dental fillings that not only last longer but could prevent further tooth decay."
The new research could produce results far beyond dentistry through the application of similar observations to test toughness in other materials. Andrew Taylor, of the Science and Technology Facilities Council's National Laboratories, says: "Neutrons have such a broad range of applications and are used by scientists looking at everything from stresses and strains in plane wings to progressing methods to producing more effective antibiotics. We can see here how a fundamental technique is applied to an everyday issue that we can all identify with."