Plastic alternatives to traditional metal braces have offered significant relief to crooked smiles everywhere. Yet, clear plastic aligners designed to straighten teeth can come with an unsavory byproduct: contamination.

The clear plastic aligners and retainers — called clear overlay appliances (COAs)— according to a report in ACS Applied Materials & Interfaces, can experience the build-up of bacteria, becoming a difficult-to-remove biofilm.

As such, scientists Hyo-Won Ahn, Jinkee Hong and colleagues, inspired by the super-hydrophilic antibacterial coatings used on other medical devices, have set out to develop a similar coating for the COAs.

The team layered films of carboxymethylcellulose and chitosan on a polymer sheet of polyethylene terephthalate modified with glycol (PETG). The result was a hydrophilic coating that halted the build-up of bacteria. The team determined that when compared with the untreated COAs, the hydrophilic layers cut bacterial growth by 75 percent.