There is archeological evidence that humans have attempted to replacing missing teeth with root form implants for thousands of years . Remains from ancient China (dating 4000 years ago) have carved bamboo pegs, tapped into the bone, to replace lost teeth, and 2000 year old remains from ancient Egypt have similarly shaped pegs made of precious metals. Some Egyptian mummies were found to have transplanted human teeth, and in other instances, teeth made of ivory.
Wilson Popenoe and his wife in 1931, at a site in Honduras dating back to 600 AD, found the lower mandible of a young Mayan woman, with three missing incisors replaced by pieces of shell, shaped to resemble teeth. Bone growth around two of the implants, and the formation of calculus, indicates that they were functional as well as esthetic . The fragment is currently part of the Osteological Collection of the Peabody Museum of Archaeology and Ethnology at Harvard University.
The early part of the 20th century saw a number of implants made of a variety of materials. One of the earliest successful implants was the Greenfield implant system of 1913 (also known as the Greenfield crib or basket). Greenfield's implant, an iridioplatinum implant attached to a gold crown, showed evidence of osseointegration and lasted for a number of years.The first use of titanium as an implantable material was by Bothe , Beaton and Davenport in 1940, who observed how close the bone grew to titanium screws, and the difficulty they had in extracting them. Bothe et al. were the first researchers to describe what would later be called osseointegration (a name that would be marketed later on by Per-Ingvar Brånemark). In 1951, Gottlieb Leventhal implanted titanium rods in rabbits. Leventhal's positive results led him to believe that titanium represented the ideal metal for surgery.
In the 1950s research was being conducted at Cambridge University in England on blood flow in living organisms . These workers devised a method of constructing a chamber of titanium which was then embedded into the soft tissue of the ears of rabbits. In 1952 the Swedish orthopaedic surgeon, Per-Ingvar Brånemark, was interested in studying bone healing and regeneration. During his research time at Lund University he adopted the Cambridge designed "rabbit ear chamber" for use in the rabbit femur. Following the study, he attempted to retrieve these expensive chambers from the rabbits and found that he was unable to remove them. Brånemark observed that bone had grown into such close proximity with the titanium that it effectively adhered to the metal. Brånemark carried out further studies into this phenomenon, using both animal and human subjects, which all confirmed this unique property of titanium. Leonard Linkow, in the 1950s, was one of the first to inserted titanium and other metal implants into the bones of the jaw. Artificial teeth were then attached to these pieces of metal. In 1965 Brånemark placed his first titanium dental implant into a human volunteer. He began working in the mouth as it was more accessible for continued observations and there was a high rate of missing teeth in the general population offered more subjects for widespread study. He termed the clinically observed adherence of bone with titanium as "osseointegration".
Since then implants have evolved into three basic types :
1-Root form implants; the most common type of implant indicated for all uses. Within the root form type of implant, there are roughly 18 variants, all made of titanium but with different shapes and surface textures. There is limited evidence showing that implants with relatively smooth surfaces are less prone to peri-implantitis than implants with rougher surfaces and no evidence showing that any particular type of dental implant has superior long-term success.
2-Zygomatic implants; a long implant that can anchor to the cheek bone by passing through the maxillary sinus to retain a complete upper denture when bone is absent. While zygomatic implants offer a novel approach to severe bone loss in the upper jaw, it has not been shown to offer any advantage over bone grafting functionally although it may offer a less invasive option, depending on the size of the reconstruction required .
3-Small diameter implants are implants of low diameter with one piece construction (implant and abutment) that are sometimes used for denture retention or orthodontic anchorage.
A typical implant consists of a titanium screw (resembling a tooth root) with a roughened or smooth surface. The majority of dental implants are made out of commercially pure titanium, which is available in four grades depending upon the amount of carbon, nitrogen, oxygen and iron contained . Cold work hardened CP4 (maximum impurity limits of N .05 percent, C .10 percent, H .015 percent, Fe .50 percent, and O .40 percent) is the most commonly used titanium for implants. Grade 5 titanium, Titanium 6AL-4V, (signifying the titanium alloy containing 6 percent aluminium and 4 percent vanadium alloy) is slightly harder than CP4 and used in the industry mostly for abutment screws and abutments. Most modern dental implants also have a textured surface (through etching, anodic oxidation or various-media blasting) to increase the surface area and osseointegration potential of the implant.
If C.P. titanium or a titanium alloy has more than 85% titanium content it will form a titanium biocompatable titanium oxide surface layer or veneer that encloses the other metals preventing them from contacting the bone.