Dental Breakthrough Could Phase Out Resin, Ceramic Fillings

Enamel remineralization, or the regrowing of tooth enamel, remains the most formidable challenge in the field of bionics. But a team of researchers from China has now found a way past this formidable barrier to develop a special gel that allows tooth enamel to repair itself.

Regrowing tooth enamel has been regarded as well nigh impossible before because tooth enamel is a highly mineralized biological tissue. Tooth enamel is also a purely inorganic substance that cannot self-repair for lack of cells and a bioorganic matrix.

It's the hardest tissue in the human body and contains the highest percentage of minerals (at 96%). Tooth enamel is some 2 mm thick on average.

Despite its toughness, this translucent substance is susceptible to degradation. It is especially vulnerable to acids from food and drink. Once enamel is damaged, people develop tooth cavities, which can trigger almost unbearable pain.

Previous attempts to regrow enamel by using a range of artificial materials such as composite resins, ceramics and amalgam failed to achieve permanent repair due to the imperfect compatibility between these artificial materials and the native enamel.

“Enamel resembles a layer of natural inorganic crystalline mineral and is primarily composed of nonstoichiometric fluoridated carbonate apatite crystals that are tightly packed with well-defined orientations to ensure striking hardness,” said Dr. Changyu Shao, lead author of the study published in the journal of Science Advances.

The efforts of a research team led by Prof. Ruikang Tang of the Zhejiang University Department of Chemistry (which includes Dr. Shao) has developed a biomimetic regenerative solution that could be applied to repair a tooth cavity.

This solution is a special gel that "will establish a biomimetic crystalline-amorphous mineralization frontier to induce the growth of enamel with a precise maintenance of the original structural complexity within 48 hours."

The research team proposed a novel approach to tooth enamel regrowth. They discovered that mixing calcium and phosphate ions -- two minerals that are the building blocks of real tooth enamel -- with the chemical triethylamine in an alcohol solution causes enamel to grow with the same structure as teeth.

The product of this mixture is a gel that encourages teeth to self-repair.

They tested the gel by applying it to human teeth removed from patients and damaged with acid. They then left the teeth in containers of fluid designed to mimic the mouth environment for 48 hours.

The study showed that when the gel developed by the research team was applied to human teeth, it repaired the enamel layer to around 2.5 micrometers of thickness. It also achieved the same structure of natural enamel within 48 hours.

“The materials we used in experiments were identical to the human tissue, thereby achieving complete structural regrowth,” Dr. Liu Zhaoming, a co-author of the study, said.

The discovery, however, hasn’t been proven to work in the “hostile environment” of the mouth, said the study. Future trials will bear this out, but it is certain regrown tooth enamel will be tested in people in the near future.

“Although we have achieved a precise duplication of the hierarchical and complicated structure in natural enamel, there are a wide spectrum of dental cavities. We need to develop our regenerative model for different circumstances so as to ensure controllability and effectiveness,” Dr. Shao said.

Dr. Helmut Cölfen, a German professor of physical chemistry at the University of Konstanz, said that to the best of his knowledge, “this has been the best tooth enamel regenerative substance so far and it has the potential to repair tooth enamel clinically in a real sense.”