Researchers Claim Enamel 'Tissue' May Be Regrowable

The days of whining drills and shrieking patients that can make a trip to the dentist an experience to dread may be numbered, according to scientists who claim that they may have found a way to regrow rotting teeth. Researchers studying tooth development have singled out a gene that controls the growth of enamel, the hard outer layer of teeth, which cannot grow back naturally once it is damaged by tooth decay. The discovery sheds fresh light on the way teeth form and could pave the way for new dental treatments that heal decayed teeth by regenerating a layer of enamel, making traditional drilling and filling obsolete. Scientists at Oregon State University found the gene after noticing that mice born without it grew teeth with no enamel covering. Tooth enamel is the hardest tissue in the body and begins to form when humans are still embryos. Specialised cells called ameloblasts in the tooth bud make enamel by releasing calcium phosphate minerals into a protein "scaffold" that shapes them into tightly packed rods of enamel. When our teeth are fully formed, they erupt from the gums and the enamel-forming cells die off, making it impossible for our teeth to regrow new enamel later.

For most animals this is not a problem, but in humans, the large amount of sugar and starch in our diet is turned into acid by bacteria living on our teeth, which slowly dissolve the enamel to make a hole in the tooth. If untreated, cavities can cause life-threatening infections in the body. If scientists can perfect a way of regrowing teeth and replacing the drill in the dentist's surgery, it could have important knock-on effects for patients. In 2005, a survey by researchers at the University of Toronto found that 5% of patients were extremely anxious about visiting the dentist, and half were so afraid that they either cancelled their appointment or failed to show up. By missing appointments, patients risk turning a fairly minor dental problem into a serious risk to their health. Last year, a poll by the Irish Dental Association found that parents passed on their fear of dentists to their children by telling them they were being brave or had nothing to fear from a visit. Despite rates of dental cavities falling for the past 30 years, almost half of children and adolescents and more than 55% of adults in the UK are still affected by holes in their teeth. Paul Sharpe, an expert on tooth development at the Dental Institute at King's College London, said: "If you could find some way of growing ameloblasts that make enamel, you could find a way to repair teeth. "Any gene like this is worth understanding.

The more we learn about it the more we can use the information to make biological models of tooth repair." Prof Sharpe's own work focuses on using stem cells to regenerate teeth, but he said the introduction of the Human Tissue Act had made it difficult to obtain teeth from patients to do the work. "We've probably lost a year because we've not been able to get hold of the right cells, and often these are from wisdom teeth that people are choosing to have removed," he said. In the latest research, published in Proceedings of the National Academy of Sciences, a team led by Chrissa Kioussi and Mark Leid bred mice that lacked a gene known as Ctip2. They found that the gene was crucial for the enamel-producing cells to form and work properly. By understanding the genetics of tooth development, Kioussi said it may be possible to repair damaged enamel and even produce new teeth in the laboratory. Some groups have already succeeded in growing the soft tissues inside teeth, but they do not have the hard enamel covering needed to withstand chewing and biting. "Enamel is one of the hardest coatings found in nature. It evolved to give carnivores the tough and long-lasting teeth they needed to survive," said Kioussi. "A lot of work would still be needed to bring this to human applications, but it should work. It could be really cool; a whole new approach to dental health," she said.