It is thought that dental implants were, like so many things, invented by the Egyptians. Missing teeth were replaced with seashells, painstakingly trimmed and shaped, before being ‘implanted’ into the jaw with a hammer. The calcium carbonate in the shells may have been key to the success of this technique. Once wedged into slots in the jaw, it is conceivable that the shells could fuse with the human bone.
The earliest example of a metal implant dates back to Roman times. In 1998, Nature magazine described the finding in Essonne France, of a ‘wrought iron’ dental implant, discovered in the jawbone of a Gallo-Roman, dating back to the second century AD. Chemical analysis suggests that the metal had been shaped using the ancient techniques of hot hammering and folding, which were prevalent among blacksmiths of the Gallo-Roman era. Although later challenged in some quarters, it is claimed that the implant was not only a perfect fit in its socket, but that it exhibited signs of osseointegration, a concept which would not be conceived until the 20th Century.
The birth of modern implantology can be traced back to the 1950s and 60s. At this time, most clinical practitioners were working with implants made out of steel. The so-called ‘blade’ and transosteal implants relied on mechanical retention to stay fixed in place. However, a major, technological break-though, centering on the unique properties of the metallic element titanium, was about to change everything.
In 1952, Dr Per-Ingvar Brånemark of Gothenburg Sweden, made a somewhat fortuitous but momentous discovery, while carrying out microscopy studies on rabbits. He discovered that titanium oculars placed into the lower legs of the rabbits could not be removed after a period of healing, as the titanium had bonded irreversibly with the bone tissue. Brånemark’s observations regarding the properties of titanium were, at the time, as controversial as they were ground breaking, contradicting as they did the prevailing scientific theory of the day. Undeterred, his research demonstrated that the effect of joining metal with bone was indeed repeatable and that, under certain clinical conditions, titanium could be structurally integrated with human bone tissue at the histological level. Brånemark called this process osseointegration.
Importantly, Brånemark also established that the process could be reproduced in a way which was predictable, safe and durable. 1965 witnessed the first practical application of osseointegration, when he implanted titanium roots into a volunteer human patient, who was without any teeth. When the patient died in 2005, the original implants were still in place, some 40 years later.
Despite this breakthrough, osseointegration received anything but universal acceptance from the scientific community. And it was not for a further sixteen years, in 1981, when the International Journal of Oral Surgery published a ground-breaking study by Adell et al., that the way was eventually paved to worldwide acceptance and adoption of modern dental implantology.
Once commercially available, the Brånemark system dominated in the early years. Distinctive for its machined titanium surface, thread pitch and external hex joint, the product benefitted from an unparalleled reputation for excellence, based on a wealth of extensive scientific research. To the present day, over seven million Brånemark implants have been placed, and his remains one of the pre-eminent implant systems available today.
Over time, an increasing number of commercial organisations responded to the opportunity presented through osseointegration technology by marketing clone implants or implants of a slightly different design, but based essentially on Brånemark’s system. Their efforts were assisted by a 510K ruling by the US Food and Drug Administration, which approved any titanium, screw-design device for use as a human dental implant. The ruling opened the gates to a flood of new devices onto the market, many of which had little or no clinical documentation, an issue which remains to this day.
While comfortably the most well known, Brånemark was not the only pioneer of titanium implant technologies. Dr Andre Schroëder of Berne Switzerland, and his colleague Dr Ledermann had developed the concept of a titanium plasma spray coating with a one-piece, transmucosal screw. Collaborating closely with the ITI Institute, their early work was published in 1981, around the same time that Adell and Brånemark’s findings first came to prominence. Published in German, Schroëder and Ledermann’s articles, which introduced the early ITI one-piece hollow cylinder implant, had limited initial impact in the US. In fact, Schroëder’s early work received little recognition until 1988, when with Daniel Buser, he published a two-part article in the International Journal of Oral & Maxillofacial Implants, in which he shared the clinical results of their work with the hollow cylinder.
From this point on, it was Buser who led the way in further developing the ITI system. In order to gain widespread acceptance of this solution, he had to overcome a significant obstacle: the science behind the one-piece transmucosal implant was at odds with Brånemark ‘s assertion that for successful osseointegration to occur, implants must be submerged during healing. The numerous articles which he published, and with which he eventually demonstrated the feasibility of the ITI system, positioned Buser as the first genuine contender to Brånemark’s work and his machined titanium screw system.
During the 1990s, implant research and development activity increased significantly, and focused on the mechanical engineering behind the devices. Particularly important was the work of Dr Stig Hansson. He pioneered the ground-breaking concept of a using a microtextured surface, to create enhanced tissue response. He introduced micro-threading, which improved load distribution and bone retention. Hansson was also responsible for the widespread adoption of the internal conical joint, as opposed to an external hex joint, which had been present in over 90% of commercial implants until that time. In recent years, Hansson’s biomechanical concepts have become widely accepted, with virtually all of today’s implants incorporating these features in one form or another.
Implantology in the Future
The future development of implants seems to lie in nanotechnology, as has been seen recently with a chemically modified implant surface, or biotech concepts such as the introduction to the implant surface of bone morphogenetic proteins. What does seem certain is that more evolution and development will follow – and that the history of these tiny, ingenious, metal objects is not yet complete.