With a new one-year administrative supplement for his current National Institutes of Health grant, Sharukh S. Khajotia, B.D.S., M.S., Ph.D., is asking a question for which there have been little to no answers: Is the microbiome of the plaque (also known as biofilms) changed when the composition of filling materials changes?

            The NIH awards supplements for projects that are related to the parent grant and propose collaborations that didn’t exist at the time the original grant was written. In his original grant, which is ongoing, Khajotia is studying how the esterases, or enzymes, in a person’s mouth have the ability to break the ester bonds in tooth-colored fillings, leading to decay under the filling, which is called secondary or recurrent caries.

            The supplemental grant allows Khajotia to delve into the oral microbiome, where there are 700 to 1,000 species of bacteria. For the microbiome analysis, he is collaborating with two researchers in the OU College of Medicine, Department of Microbiology and Immunology, David Dyer, Ph.D., and MaJoi Trammell, B.S. Dyer and Trammell will provide bioinformatics analyses that examine the response of the salivary microbiome to changes in the chemical composition of the tooth-colored filling materials.

            “Newer technologies now make it possible for us to better study the microbiome. This project will run in parallel with the parent grant. So we’re asking two questions: Do these esterases change the chemical composition of the tooth-colored filling material, and do they also change the microbiome of the saliva?” said Khajotia, Associate Dean for Research and Innovation in the OU College of Dentistry. He recently published an article about the lack of knowledge on microbiome interactions in the Journal of Dental Research, authored by colleagues from Oregon Health & Science University.

            The ultimate aim of both grants is to decrease the number of fillings that must be replaced due to secondary caries. Although filling materials have improved considerably since the 1960s, it is estimated that in the United States alone, more than $5 billion is spent each year on replacing tooth-colored fillings, Khajotia said. 

      “If we can find a way to replace a tooth-colored filling every 14 years instead of every seven years, we can reduce the cost of oral healthcare and save more of the patient’s tooth structure,” he said. “This is a translational research study in which we will examine how these materials and the microbiome are both impacted, which will help us in the future when we are developing new filling materials.”

      Khajotia’s previous studies have shown that when the bonds break down, the surface of the filling begins to degrade and becomes rougher, which allows more plaque to form. Because filling material contains many different components, he wants to understand which of them are linked to more or less plaque formation. If those components can be identified, filling materials might be changed so that they don’t support as much plaque growth.

“We don’t know precisely what is happening to these fillings at the junction between tooth structure, the filling material and the bonding agent,” he said. “It’s a complex interface, but we are beginning to learn more about why bonded restorations fail earlier than they should.”

      Khajotia has been building his research over the years to the point where he earned the recent federal grant. In previous research funded locally by the Presbyterian Health Foundation and the Oklahoma Center for the Advancement of Science and Technology, he studied how two salivary enzymes roughen fillings. The new grant expands that research. He is using tests that he and his team developed that are now being used around the world, including a process for creating a three-dimensional structure of plaque.

      The new grant also includes funding for several dental and dental hygiene students to participate in the research, a process that benefits them greatly as they begin their careers.

      “Patient care and research go hand in hand; without one, you cannot have the other,” Khajotia said. “Most of the developments in dental biomaterials have been based on a clinical need. Our college has a history of clinical excellence, so doing research is a logical extension of our clinical capabilities.”