When Keren Shemtov-Yona, DDS, a dental researcher at the Technion-Israel Institute of Technology, examined 100 discarded dental implants under a scanning electron microscope, she found that more than 60 percent of the implants had cracks and other flaws. Because dental implants have become increasingly popular (in the U.S. alone, more than 3 million people have them), she feels that the public should be informed about the high rate of flaws in dental implants and their potential for fracturing.
Dr. Shemtev-Yona also wants to encourage dental implant manufacturers and dentists to find ways to reduce "metal fatigue" -- the localized structural damage that occurs when a metal is subjected to repeated applied loads. Over time, metal fatigue causes many of the implant-related fractures.
"Extracting and replacing a broken dental implant is a complex surgical procedure," she said. "The time has come for both the dental community and manufacturers to come to avoid unnecessary surgical procedures."
Dr. Shemtov-Yona is carrying out her doctoral studies under the supervision of Professor Daniel Rittel of the Faculty of Mechanical Engineering who co-authored a paper that will be published in the September 2015 issue of the Journal of the Mechanical Behavior of Biomedical Materials.
The implants in the study were extracted from wearers not because they were broken, but because of progressive bone loss around the titanium post that anchors them in place. All appeared to be in perfect condition prior to analysis. However, upon inspection using x-ray and scanning electron microscopy, mechanical defects were revealed in 62 percent of the implants.
"The implants were a random combination of two materials, titanium alloy (Ti-6Al-4v) and commercially pure titanium (CP-Ti)," explained Dr. Shemtov-Yona. "The CP-Ti implants had more cracks than the titanium alloy."
"Embedded particles appear to be linked to the generation of surface defects that evolve into full cracks," she pointed out. The effect of time and the wear and tear of daily use may also contribute the potential for manufacturing flaws to develop into cracks and subsequently lead to the ultimate failure of the materials of which they are made.
"Also, every individual has both different chewing habits and oral environment. Mastication can cause a repeated loading, leading to degradation of the implant materials and metal fatigue," she continued.
Dr. Shemtov-Yona conducted this study for her Masters of Science degree, and recently enrolled in a PhD program in the Department of Mechanical Engineering to get an even better understanding of the problem Her current goal is to find what leads to the development of cracks to determine whether the causes lie in manufacturing, use, or both, in order to prolong the service life of implants.
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