An innovative gel that forms a layer over teeth and then recruits calcium and phosphate ions from saliva to build new enamel has the potential to change dental treatment. To date, we don’t have any way to regenerate the tough outer layer of enamel on our teeth as it erodes with age.

Scientists from the University of Nottingham, along with international researchers, have developed what they describe as a huge breakthrough, creating a protein-based gel that can not only strengthen existing enamel but actually rebuild it. When applied to teeth, much like common fluoride treatment in the dentist’s chair, it forms a thin layer that seeps into the bone to patch up any holes or cracks. But then it also forms a type of scaffolding that attracts those other ions, which promotes further mineral “growth” through a process known as epitaxial mineralization. The new mineral deposits fuse with existing tissue to form what is essentially new enamel.

“Dental enamel has a unique structure, which gives enamel its remarkable properties that protect our teeth throughout life against physical, chemical, and thermal insults,” said lead author Dr. Abshar Hasan, a postdoctoral fellow at the University of Nottingham. “When our material is applied to demineralized or eroded enamel, or exposed dentine, the material promotes the growth of crystals in an integrated and organized manner, recovering the architecture of our natural healthy enamel.”

According to the World Health Organization, an estimated 3.7 billion people worldwide have some form of oral disease, and the erosion of enamel – the tough, mineralized protective outer layer of our teeth – is a massive contributor to one of the largest issues, tooth decay. This comes about from a suite of chemical and mechanical triggers, including frequent consumption of acidic and sugary foods like soda and fruit juice, tooth grinding, aggressive brushing, acid reflux and even dry mouth. And because we can’t currently repair any enamel we lose, it can lead to chipped or cracked teeth and cavities. And while fluoride is important, it doesn’t repair what’s already been eroded.

“To tackle this issue, we engineer a tunable and resilient supramolecular matrix based on elastin-like recombinamers that imitates the structure and function of the enamel-developing matrix,” the researchers noted. “When applied as a coating on the surface of teeth exhibiting different levels of erosion, the matrix is stable and can trigger epitaxial growth of apatite nanocrystals, recreating the microarchitecture of the different anatomical regions of enamel and restoring the mechanical properties. The study demonstrates the translational potential of our mineralizing technology for treating loss of enamel in clinical settings such as the treatment of enamel erosion and dental hypersensitivity.”

Electron microscopy images of a tooth with demineralized enamel showing eroded apatite crystals (left) and a similar demineralized tooth after a two-week gel treatment, showing epitaxially regenerated enamel crystals (right)

University of Nottingham

The researchers used extracted human molars as an ex vivo model, first etching their enamel or dentine surfaces with acid to mimic different stages of tooth erosion. They then applied a single coating of the biomimetic elastin-like recombinamer (ELR) gel and let it dry. Finally, the teeth were immersed in carefully controlled mineralization baths that replicated the ionic environment of saliva. Over about 10 days, the ELR coating passively attracted calcium and phosphate ions from the fluid, enabling them to crystallize within its scaffolding. This led to the epitaxial growth of fluorapatite nanocrystals, which essentially mirrored the structure and strength of natural enamel.

The scientists then put the newly strengthened teeth to the test. Through electron microscopy, the team was able to confirm that the new apatite crystals grew seamlessly from the underlying enamel or dentine, showing continuous lattice alignment but without it being visible to the naked eye. Nanoindentation tests revealed that the remineralized enamel was nearly identical to healthy enamel. And when daily wear and tear was simulated – through continuous electric-toothbrush abrasion equivalent to about a year of brushing, as well as chewing and grinding – the teeth actually had superior resistance to wear, fracture and acid attack compared with natural enamel. Tests in both artificial and real human saliva produced the same result, demonstrating that the single-application ELR coating could recreate enamel and withstand real-world impacts.

“We are very excited because the technology has been designed with the clinician and patient in mind,” said Professor Alvaro Mata, Chair in Biomedical Engineering & Biomaterials at Nottingham University. “It is safe, can be easily and rapidly applied, and it is scalable. Also, the technology is versatile, which opens the opportunity to be translated into multiple types of products to help patients of all ages suffering from a variety of dental problems associated with loss of enamel and exposed dentine. We have started this process with our start-up company Mintech-Bio and hope to have a first product out next year; this innovation could soon be helping patients worldwide.”

It’s worth noting that these results are preliminary, as tests were conducted ex vivo under controlled conditions. What’s more, the ELR layer was only a few micrometers thick – thinner than natural enamel – so its long-term durability is unknown.

However, the gel presents a promising pathway forward in enamel regeneration – one that requires further development and testing before we’re likely to be adding it to our teeth after a morning brush.

The research was published in the journal Nature Communications.

Source: University of Nottingham