A Concrete Relationship
words by merry sue baum / photograph by andrew hanenberg
verything on earth has a breaking point. No matter what the material, if it is twisted, rammed, stretched, compressed or laden enough, it will eventually fail.
No one knows that better than Allyn Luke, MSCE, a nationally renowned expert on concrete who teaches concrete design and is the director of the concrete laboratory at New Jersey Institute of Technology (NJIT). He’s been a consultant to the Department of Transportation for more than 20 years, doing research and testing New Jersey’s roads and bridges for safety and durability. Beginning in 1998, however, the civil engineer took on a new role: dental researcher.
Luke was recruited by Saul Weiner, DDS, a professor of restorative dentistry at New Jersey Dental School (NJDS). When he needed engineering expertise to continue his research on dental implants and biomaterials, Weiner traveled a few miles to NJIT. There he met Luke, and the two have been working together since. “Allyn has a profound knowledge of mechanical structures and the physical properties of concrete,” says Weiner. “Believe it or not, concrete and dental materials are very much alike; both are very brittle and subject to crumbling. Allyn is also an expert in using Material Testing Systems (MTS). We are one of only two dental schools in the U.S. that has a multi-axial MTS, or one that moves in a chewing-like motion.”
An MTS is a highly precise, complex, computerized system that tests materials under various conditions to measure their toughness, flexibility and overall strength. NASA and the automobile and aircraft industries routinely use them, for example, to test screws that hold engines, wings and seatbelts in place. The dental school’s MTS simulates the mechanics of chewing and the oral environment. “The environment in the mouth is tough, with dramatic acidity and temperature changes and fatiguing forces that take a toll on restorative materials and implants,” says Weiner. “The MTS is extremely important to our research, since we are looking to design the best possible implants and materials.” Luke, now a volunteer adjunct assistant professor at NJDS, maintains it and advises and teaches faculty members and postgraduates in its use. He is an integral part of the Restorative Dentistry Department’s research team, helping to design protocols and participating in data analysis and publication. He does all this when he’s not at NJIT. “I consider Luke a huge asset to our research,” says Ajay Dhingra, DMD, a former NJDS postgraduate who is now an assistant professor at the University of Connecticut School of Dentistry. “I hold him in the highest esteem and truly appreciate his help.” Other researchers are associate professors David Ehrenberg, DDS, and Hoda Yousef, DMD, and professor T.K. Vaidyanathan.
In order to understand their research, it is necessary to know a little about dental implants. They are artificial tooth roots made of titanium that are screwed into the jawbone. A tooth-like crown is then attached with tiny screws. “Implants are now a common substitute for worn or missing teeth, so patients’ expectations are becoming greater as the technology improves,” says Weiner. “They want their implants to look and hold up like natural teeth.”
Dr. Yousef focuses on the tiny screws that hold the crowns in place. “They are similar in size to the screws in eyeglasses,” she says. “We’re working to maximize their longevity, since we want them to last a lifetime.” Dr. Dhingra looks at the stability of ceramic units, which have a tendency to be brittle, like glass. Other areas of research include stability of prostheses, including bridges and dentures, which are supported by implants, and sensory control of jaw movements associated with them.
The team has published papers that are unique in the literature in several prestigious journals, including the International Journal of Oral and Maxillofacial Implants and Implant Dentistry. Among the things they’ve learned: a single implant does not hold up as well as two or more adjacent to one another and it is not beneficial to replace the screws every five years. They also have a theory on why ceramic abutments are durable, even though brittle. They believe the fine sand produced as the ceramic wears provides traction, similar to sand under the tires of a car stuck in the snow.
The unique partnership is the proverbial win-win situation. “It is quite an honor to have Luke with us,” says Weiner. And Luke loves being a dental researcher. “No matter what the size of a bridge, if it’s a 1,000-foot-span or the small space where there once was a tooth, the same basic, guiding principles apply,” Luke says. “It’s gratifying to be able to help with this research, and it’s fun.” .