Here's how it works. The replacement tooth is designed to match the gap in the person's mouth. A resin, made of safe materials combined with a special salt, is then printed into the shape of the tooth and then placed like a normal replacement into the person's mouth. The positive charge in the salts in the resin bursts negatively-charged bacterial membranes, leaving only dead colonies where once were festering feeding frenzies of microbial intruders.

To test the work, they printed objects both with and without the microbial salts, and then put tooth decay-causing Streptococcus mutans on the samples. Without the salts, only about 1 percent of the bacteria on the items died. With the incorporated salts, over 99 percent of colonies vanished.

The authors of the paper are enthusiastic about its success and future uses, writing:

The antimicrobial properties were shown to be caused by bacterial contact killing with the material rather than the release of antimicrobial compounds from the resin. Having optimized the activity and stability of these materials, we have a prototype at hand that is suited for further testing in a clinical setting, including not only dental applications but also, for instance, orthopedic ones like spacers and other polymeric parts used in total hip or knee arthroplasties. Moreover, the approach to developing 3D printable antimicrobial polymers can easily be transferred to other nonmedical application areas, such as food packaging, water purification, or even toys for children. To the best of our knowledge, the resins we developed represent the first report of an antimicrobial, contact-killing 3D printable material.

[New Scientist]