Experts produce clusters of enamel-like calcium phosphate to crack age-old problem
Scientists say they have finally cracked the problem of repairing tooth enamel.
Though enamel is the hardest tissue in the body, it cannot self-repair. Now scientists have discovered a method by which its complex structure can be reproduced and the enamel essentially “grown” back.
The team behind the research say the materials are cheap and can be prepared on a large scale. “After intensive discussion with dentists, we believe that this new method can be widely used in future,” said Dr Zhaoming Liu, co-author of the research from Zhejiang University in China.
Tooth decay is extremely common: according to 2016 figures about 2.4 billion people worldwide live with caries in permanent teeth, while 486 million children have decay in their milk teeth
At present, materials such as resin, metal alloys, amalgam and ceramics are used to repair damaged tooth enamel but they are not ideal.
“The resin-based material still cannot adhere well on enamel, and they will get loose after around five years,” said Liu.
While scientists have been chipping away at the issue for years through a number of approaches, they have encountered problems – not least that it is difficult to reproduce the complex structure of natural tooth enamel.
The researchers behind the latest study, published in the journal Science Advances, say they got around this problem by developing a way to produce tiny clusters of calcium phosphate – the main component of enamel – with a diameter of just 1.5 nanometres – far smaller than those previously employed.
That was managed by preparing the clusters in the presence of a substance called triethylamine that prevented them from clumping.
To test their clusters, the team used crystalline hydroxyapatite, which is similar to natural enamel. The results showed the clusters fused on to this material and formed a layer with a much tighter arrangement than previous, larger clusters.
The team says this is important because it means that as the new layer transforms and becomes crystalline over time, it extends the underlying structure in a continuous manner, rather than forming many crystalline regions.
The team then applied their clusters to human teeth which had been exposed to acid. They discovered that within 48 hours the clusters had given rise to a crystalline layer, about 2.7 micrometres thick, with the complex, fish-scales-like structure of the underlying natural enamel.
The repaired enamel had a similar strength and wear-resistance to natural, undamaged enamel.
Dr Sherif Elsharkawy, an expert in prosthodontics at King’s College London who was not involved in the work, praised the research and said he found the approach very exciting.
“The method is simple, but it needs to be validated clinically,” he said, adding that it could be several years before the method be used in dental practices.
Elsharkawy said layers would need to be scaled up to 0.5 to 2mm in thickness to tackle cavities.
While Liu and colleagues agree that the thickness of the layer is a limitation, they are working on ways to improve this. Liu said the team hoped to use it in a trial in humans in one to two years.