Osteoporosis drugs called bisphosphonates have been linked with the development of osteonecrosis (bone death) in the jaw. Researchers at the University of Southern California (USC) School of Dentistry say they have identified an infectious cause of bone death in some people taking the drugs to prevent bone loss – a mix of bacteria and sticky extracellular material, called microbial biofilms.

Their study – which used powerful electron microscopes to examine osteonecrosis jaw bone samples from patients of USC dental clinics who had the unusual problem – is the first study that identifies microbial biofilms in the bone of bisphosphonate patients who have osteonecrosis of the jaw, says lead researcher and USC assistant clinical professor Parish Sedghizadeh. In affected jaws, the images revealed biofilm bacteria sprawling over pitted tissue.

Jaw osteonecrosis occurs when bacteria-laden biofilms infect the jaw after the bone is exposed, typically because of a tooth extraction or injury, he says.

Pioneered by J. William Costerton, director of the Center for Biofilms at the USC School of Dentistry, the biofilm theory has moved scientists beyond thinking of bacteria as free-floating organisms. Instead, bacteria build biofilm communities, attaching to surfaces and communicating and defending against antimicrobial invaders.

While the researchers are still trying to determine why bisphosphonate drugs seem to open the door for biofilm-associated infections of the jaw, knowing the culprit behind the damage is an important step toward controlling it.  "Now that we know that biofilms are behind the infection of the jaw, we are studying ways to effectively treat or prevent the osteonecrosis," Sedghizadeh said. The study was published in the Journal of Oral and Maxillofacial Surgery.