The prospect of losing a tooth is never pleasant, but modern dentistry continues to make the problem more manageable. Over the last decade the field has been transformed by implant technology, which inserts a replacement tooth – complete with a metal root – directly into the jawbone. In contrast to the crowns and bridges that have traditionally filled gaps between teeth, these well secured devices can be much more stable and robust.
Nevertheless, the success of such an implant depends on how well its metallic surface bonds with the jaw, a question that intrigues Kathryn Grandfield. As an assistant professor in McMaster University’s Department of Materials Science and Engineering, she has developed a dedicated approach to studying the complex chemistry at the interface between an implant and its biologically active setting.
The results of her latest work appear in a recent paper for the journal Advanced Materials Interfaces, which details the combined use of tomographic and spectroscopic imaging techniques to reveal how intricate laser etching on a titanium implant influences biomineralization to bond metal to bone.
“We looked at the area inside this laser-modified surface to see how the bone integrated into the nano-scale architecture of the implant,” she explains. “We can see an oxide layer on the surface, with different regions that are rich in proteins penetrating all the way into this oxide layer and even chemical signatures that mimic bone mineral.”
Grandfield regards McMaster as an outstanding place to conduct this detailed analysis, since she is also director of operations for the Canadian Centre for Electron Microscopy, with its unrivalled assortment of powerful instruments located right on campus. By painstakingly rotating an implant sample in minor increments, her team was able to get the Centre’s Transmission Electron Microscope to produce the kind of three-dimensional imagery that would ordinarily emerge from a Magnetic Resonance Imaging system, but with much higher resolution. They did the same with Canada’s atom probe microscope, which evaporated atoms individually to achieve what Grandfield calls a 4D picture, complete with locational and chemical information. Grandfield also collaborated with McMaster Chemistry Professor Adam Hitchcock, FCIC, who used the soft X-ray beam line at the Canadian Light Source in Saskatoon to conduct further spectromicroscopy on the same sample, thereby providing detailed spectroscopic information to complement the electron microscopy and atom probe studies.
Understanding implant failures has become a major priority as ever greater numbers of dentists and dental specialists turn to this technology. Failure rates remain hard to determine, since organizations like the Canadian Dental Association only speak generally about implant innovations and companies that manufacture these products are guarded about the state of their business activity. Many of the published statistics in the field date from at least a decade ago, when the market for dental implants began to take off, while the details of their current use are largely proprietary.
For example, a 2006 article in the Journal of the Canadian Dental Association suggested this country’s market for dental implants was around $70 million, about double what it had been in 2002. That amount pales in comparison to estimates put forward by the American Academy of Implant Dentistry, which foresees a US and European market that will reach $4.2 billion by 2022. That organization states that 15 million Americans have crowns or bridges to replace missing teeth, but some three million have already been outfitted with implants, a number expected to rise by at least 500,000 annually.
While it may not be clear just how many of these implants fail, Grandfield is hoping her work sheds light on why they might fail. The research has already revealed an unexpected layer of nitrogen under the surface of the implant, which could be a side effect of the laser action.
We thought there was only a titanium oxide layer on the surface, but we found just under the surface there was also a titanium nitride layer,” she said. “That might influence the way the implant reacts in the body or its longevity.”