19.1. A CONCISE HISTORY OF DENTAL IMPLANTOLOGY
Dental implantology itself is a long story to tell. Millennia ago the idea of implanting artificial teeth instead of the lost ones existed. Archeological findings indicate that 4000 years ago in ancient China bamboo was implanted into the jaw in order to substitute a missing tooth, and more than 2000 years ago, in the territory of ancient Egypt and Europe, iron and precious metals were used with the same purpose. For implant surgery, stones, precious gems and metals, ivory, sea mussels’ shells and other materials were in use. Attempts to re-implant lost teeth were also made. Tooth replacement procedures were divided into two types: reimplantation, i.e. grafting into its original place, and transplantation including various cases. However, widespread of such diseases as syphilis and tuberculosis and their possible transmission through transplantation caused criticism of this discipline.
Scientific foundation for allotransplantation in dentistry was laid only on the cusp of the 19th-20th centuries. During this period, root-shaped dental implants, reminders of ancient designs, were created. Searching of suitable materials for dental implant surgery became an important task. In 1807, J. Magillo placed a golden implant in the alveolar socket after the tooth extraction, and a crown on the supragingival part of the engrafted implant, all in one stage. Attempts were also made to engraft lead implants with rough ends, carrying a platinum pin and a porcelain crown, made of gold and iridium, silver and corrugated porcelain, platinum. It is worth to mention the authenticity of the construction designs and implanting methods of each proposed implants. However, it is quite complicated to summarize and objectively evaluate implant surgery results of those years, since before the introduction of the concept of “antisepsis” into surgery by Lister, surgical wounds were nearly always infected and implant failure was a common occurrence. The use of antiseptics significantly reduced the risk of surgical wounds’ infection, which led to tremendous advances in all areas of medicine, including implant surgery.
Another step in the development of dental implantology was made by A. Hartmann (1891), who screwed dentures to the engrafted structures. Audacious and experimental researches carried out by N.N. Znamensky were also of great importance for dental implantology.
The author came to the fundamental conclusion that an implant can be made of porcelain, metal or other durable, but nonresorbable material, and has to be placed under aseptic conditions into an artificially formed implant site. His works received a positive response in foreign press, though they were forgotten for many years in Russia.
Along with the search for material, a reliable and the most suitable implant design was yet to be found. In 1913, E.J. Greenfield used a hollow basket made of iridium wire with a 24 carat gold clasp-like solder in order to fix the crown. The author paid attention to the necessity of working out a special technique of creating an implant site. A carbide drill was used to create a tooth socket. This implant was utilized solitary and in groups of up to eight units. It can be considered as a predecessor of modern hollow implants. In 1937, R. Adams patented a cylindrical implant with thread, round base, smooth gingival rim and protective therapeutic pad. A round head was screwed to a root in a modern manner in order to fix a removable denture.
Physical, chemical and biological properties of materials for allotransplantation often determined inadequate osseointegration and implant failure, and caused surgery fiasco in general. For many years it was the reason of implants’ non-acceptance in the oral surgery practice.
The active development of dental implantology as an independent and scientifically based direction in dentistry started with the utilizing of cobalt-chromium alloy “Vitallium” as an implant material coming with high corrosion resistance to electrochemical action of interstitial fluid. Despite subsequent advances, cobalt-chromium alloy was used as an implant material until the end of the 20th century.
In 1940s, fundamental researches in implantology were conducted: in Russia - on maxillofacial implant surgery (creation of implant systems used in plastic surgery, traumas); in other countries - on dental structures. In 1940, a favorable effect of bone contact with titanium was highlighted by R. Bothe et al. in the research devoted to comparative study of bone tissue response to implants made of various materials. Titanium has been used for the manufacturing of surgical instruments and implants since 1951.
Since 1952, studies on the response of biological tissues to titanium have been carried out in the morphological laboratory and then in the Department of Experimental Biology of the University of Gothenburg under the tutelage of P.I. Branemark. The result of these studies was the discovery and substantiation of the principles of forming a tight contact with the surface of a titanium plate that was atraumatically engrafted in a prepared implant site that exactly matched the shape of the implant. This phenomenon was named as osseointergation, and in 1977 P.I. Branemark defined it as “the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant that can be verified microscopically”. However, it took some time to recognize titanium as the perfect material for the implant manufacturing.
Until 1970s, the issue of the material for implants to be made of, that would simultaneously have necessary durability to the action of chewing forces and tolerance to the surrounding tissues, remained relevant. Thereby, the shape of implants was determined by the advantages and disadvantages of the material itself (elasticity, fragility, resistance to stress). This period is determined by the active elaboration of the main types of the dental implants, well-executed designs of which have got even further development and are being utilized nowadays.