In the 1950s, researchers at Cambridge University devised a method to construct a titanium chamber which was then places into the soft tissue of the ears of rabbits. Two years later, P I Branemark, a Swedish orthopedic surgeon who was studying bone healing, used the titanium chamber method in the rabbit femur. After several months of study, Branemark tried to retrieve the titanium chambers, but found that the chambers are not removable. He noted that the bone had grown around titanium and adhered to the metal chamber. Further studies in animal and human subjects confirmed that titanium has a unique property which makes it able to adhere to the bone structure. Later, an Italian doctor Stefano Melchiade Tramonte started using titanium for dental restorations on many of his patients. In 1966, he published the results of his clinical studies. Meanwhile Branemark continued his research and published many studies on the use of titanium in dental implantations and eventually made a partnership with a Swedish defense company to focus on the manufacturing and marketing of titanium-made dental implants. To this day, more than 7 million Branemark System dental implants have been placed. Hundreds of other companies are also manufacturing dental implants using Branemark's methods.