Imaging Reveals Bur Debris Under Composite Fillings

Richard Gawel


Dentists rely on burs to prepare tooth structures for fillings. Yet the drilling process may leave bur debris on the floor of the prepared surface of the teeth and even under the restoration, placing it in direct contact with the tubules and fluid within the dentin.

Using nondestructive microcomputed tomography, a team of researchers searched for remaining bur debris under composite restorations. They employed a synchrotron-based x-ray absorption technique at the BioMedical Imaging & Therapy 05ID-2 beamline at the Canadian Light Source facility in Saskatoon.

“Synchrotron-based x-ray imaging provides unique benefits to biomedical research,” said Dr. Assem Hedayat, lead author of the study. “Unlike x-rays from conventional radiographic equipment, synchrotron light is monochromatic, polarized, extremely intense, and fine-tunable, allowing us to image teeth and dental fillings with micrometer-scale resolution and to quantify tissue and material properties.”

Also, the monochromatic x-rays used for the synchrotron-based imaging minimize the beam-hardening effect in the images compared to the spectrum x-rays of conventional radiography. The researchers performed their imaging at 50 keV at a pixel size of 4 µm to reveal the dental bur fragments under a composite resin dental filling.

Dispersive x-ray spectroscopy elemental analysis of the dental bur edges showed that the fragments were made of tungsten carbide-cobalt, which is bio-incompatible. While Hedayat says that more studies are needed to determine the health risks of such debris, he notes that there is no evidence that such patients are currently suffering from any ill effects.

Furthermore, Hedayat says there is no evidence that these materials typically aren’t completely removed during restorations, and more research is needed to determine how frequently they are left behind. He adds that dentists probably do an excellent job already in ensuring that these materials are removed before the restoration is placed.

“This was an incidental finding of a dental materials study,” Hedayat said. “In this investigation, the conditions under which the teeth were prepared (‘drilled’) differed from the usual procedures used in a dental office, and high-volume suction employed during preparation of tooth material during these procedures would remove all or the vast majority of the bur fragments.”

The study, “Synchrotron-Radiation-Based X-Ray Micro-Computed Tomography Reveals Dental Bur Debris Under Dental Composite Restorations,” was published by the Journal of Synchrotron Radiation.

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