Summer Student Research: Development of an Antimicrobial Dental Composite

Cori J. Ballard, a second-year dental student, spent her summer investigating the antimicrobial properties of K18 Quaternary Ammonium Silanes (QAS) and its effectiveness as an antimicrobial additive to dental composites, a resin material used to restore teeth such as fillings. K18 QAS is not a new substance, Ballard explains, but instead an additive commonly used in hand sanitizer and oral cavity cleansers for its ability to kill bacteria. As she explains it, K18 QAS is a molecule with a long alkyl chain, shaped like a sword. “This sword is able to pierce the cell membranes of bacteria causing damage and death by cell lysis,” Ballard said. “By utilizing a mechanical mechanism to induce cell death, bacteria are unable to become resistant.” This capability led Ballard, under the guidance of her research mentor, Kyumin Whang, MS, PhD, a professor in the Department of Comprehensive Dentistry, to incorporate a K18 QAS functionalized methacrylate resin (K18 QAMS) and K18 QAS Barium glass filler to form a dental composite that she hoped would have the ability to continuously kill bacteria even as it endures normal wear and tear. Since the composite material would be infused with K18 QAS, Ballard explains that normal surface wear would expose fresh K18 QAS and QAMS to keep bacteria at bay without affecting the composite’s other properties, such as its strength or durability. To begin testing her hypothesis, Ballard performed six different experiments on K18 QAS infused dental composites. These preliminary investigations tested the composite’s cure or how it sets and hardens, and its mechanical and antimicrobial properties. Ballard’s first round of testing found that adding K18 QAS to the composite did not affect how it set, however she did notice that due to its molecular bulk, adding the K18 QAS Barium glass filler weakened the material by preventing important bonds within the resin. The tests on the resin’s antimicrobial effects were inconclusive at this stage. Ballard intends to continue her study of K18 QAS by increasing its concentration in the composite and discovering a solution that keeps the composite’s strength intact. Ballard, along with other dental students who participated in the summer student research program, will provide a presentation of their work during a Dental Research Seminar this fall; details are forthcoming. Her research is titled, “Development of an Antimicrobial Dental Composite using Quaternary Ammonium Silane (K18 QAS) Functionalized Methacrylate Resin and K18 Barium Glass Filler”.