Potentially hazardous dental bur debris under fillings

Dental burs are used extensively in dentistry to mechanically prepare tooth structures for restorations (fillings); dental burs can be made of stainless steel, diamond or tungsten carbide (WC) cemented with cobalt or nickel. Generally, dental burs come in different kinds and shapes. Each of these kinds of burs is used for a specific function when drilling into the crown of a tooth to create a cavity in which filling material is placed. Stainless steel burs are used if the cutting is pursued at speeds slower than 5000 rpm, while at high speeds diamond-coated burs are most efficient in carving the brittle enamel, and WC burs are most efficient in cutting dentin.

Little has been reported on the bur debris left behind in the teeth, and whether it poses potential health risks to patients. The bur debris can remain within the prepared tooth structure, or be ingested or inhaled, and, owing to their sharp edges, can become lodged in soft tissue. In one study, magnetic resonance images revealed the presence of dental bur artifacts in both second premolar areas of the mandible.

A group of scientists in Canada [Hedayat et al. (2016). J. Synchrotron Rad. 23, doi:10.1107/S1600577516002198] aimed to image dental bur debris under dental fillings, and allude to the potential health hazards that can be caused by this debris when left in direct contact with the biological surroundings, specifically when the debris is made of a non-biocompatible material.

Non-destructive high resolution micro-computed tomography using hard X-rays 05ID-2 beamline at the Canadian Light Source was used to image dental bur fragments under a composite resin dental filling. The bur’s cutting edges that produced the fragment were also chemically analysed. The technique revealed dental bur fragments of different sizes in different locations on the floor of the prepared surface of the teeth and under the filling, which places them in direct contact with the dentinal tubules and the dentinal fluid circulating within them. Dispersive X-ray spectroscopy elemental analysis of the dental bur edges revealed that the fragments were made of tungsten carbide-cobalt, which is bio-incompatible.

The amount of bur fragments found in the teeth is small, and it is uncertain if, or to what degree, this constitutes a biohazard to patients. Accordingly, further research is needed to investigate the effect of the non-biocompatible dental bur fragments.