Bite - In

This months Rewind is a very interesting and one of the most revered areas of dentistry today. Dr. Ajit Shetty takes you down memory lane exploring the past and the today of the science of Implantology.

HISTORY OF IMPLANTS

Even early man knew the importance of having a good dentition. Teeth have been used as a weapon for offence and defence. The loss of teeth and the debilitating effects on the general health and power was understood even then. Teeth have been shaped, sawed, veneered to enhance beauty, show wealth and power.

Endosteal implants probably started in Early Egypt, where the rich had their teeth replaced by extracted teeth from slaves or poor people who would sell it to them. When human teeth were unavailable even teeth from animals such as goats, dogs and monkeys were used. It was in the early sixteenth century that man started reimplanting teeth that had been accidentally avulsed. Towards the end of the nineteenth century, Bugnot attempted to use tooth buds. About the same time, in 1886, Younger transplanted teeth into artificially created sockets.

The last two decades of the century saw the use of all kinds of materials such as porcelain, gutta percha and platinum. In the 1940’s Formiggini developed a screw type of implant. Chercheve introduced in 1962 another screw type of implant made of chrome cobalt which became very popular. A serious draw back with this implant was that it was unable to withstand any lateral forces. It was in 1967 that Hodosh used acrylic resin in the form of a tooth and tested these implants on monkeys. Since acrylic was easy to shape and was resistant to corrosion unlike most metals, it was, therefore the material of choice. These implants were made with a porous root type structure which was said to allow ingrowth of bone, but unfortunately this was not to be. Linkow in 1966 developed the blade type of implant and used to fabricate them from chromium nickel and vanadium. These were single step procedures, where implants were introduced through the mucosa into the bone. Subsequently a lot of workers tried to develop blades of various designs and of different materials all of which resulted in varied success rates. Currently these blades are being made from titanium, ceramic (monocrystalline forms ) and memory alloys, all being very bio compatible materials.

The concept of fibro osseous integration was given a tremendous boost by Dr.Charles Weiss, who developed a blade implant system, where he used single stage blades, inserted these into the jaws, sutured the flap and immediately fabricated a temporary prosthesis. This was cemented on the implant essentially within 24 hours and the patient was asked to chew on that. This resulted in that there was a fibrous interface between the bone and the blade and this was claimed to be functioning like the periodontal ligament. Microscopic studies revealed that the fibrous capsule that did form was not directional in its attachment to either surface and unlike the periodontal ligament would not assist in handling the forces rendered on the implant.

One other major difference was the method of preparation of the osteotomy for the insertion of the implant. Unlike all other modern implant systems that have stressed on the need of gradual precise congruent enlargement of the implant osteotomy site, he advocated the use of an air rotor handpeice and free handed the slot preparation. The last two to three decades saw further improvement in blade design, whereby stress distribution to the implant bone interface has been well balanced and the use of bio compatible material such as titanium. Further the development of two stage blades with more precise instrumentation developed by Hans Graffelman have increased the success rates to almost a 96 % value.

In 1975, Hodosh et al developed implants made of a bio compatible material--vitreous carbon. These implants had a fibrous band which was claimed to be well organized and which could compare favorably to natural periodontal ligaments, with added advantage of bone ingrowth since the material was bio compatible. These implants were used as a single tooth replacement inserting them into bone sockets. They were made from 99.99 % pure carbon and this had a stainless steel sleeve for strength . Though there was a claim of 70 % success in experiments on baboons the results in clinical trials were not as successful. One other material -- ceramic which was used way back in 1880, a bio compatible inert material reemerged in 1960’s in newer forms. The brittle nature of this material caused it to fail and to overcome these problems the monocrystalline forms were developed which were much stronger. These were basically developed in Japan and good results were claimed in the mandible. The implant soft tissue interface was similar to the that between natural tooth and the gingiva. Like all great discoveries of this world that of titanium as ann accident Dr Branemark an orthopaedic surgeon inserted a titanium chamber into the tibia of a rabbit to study microcirculation in box repair mechanisms. After the completion of the study when he tried too remove the chamber he realised that it was fixed good and proper and realized that there was a strong bony anchorage.

From this resulted the development of the dental implant. Titanium implants were placed into jaw bones of dogs and fixed prothesis were fixed onto these annd the results were evaluated at different time intervals. On the basis of these results a foundation for osseo integration and the Branemark implant system was established in 1952. Basic research was carried out and the clinical use began in May 1965. Controlled clinical trials and careful documentations that followed over the folllowing 15 to 20 years period resulted in a wealth of information which resulted in the world sitting up and taking notice of this predictable modality of tooth replacement and this is how it came to stay.

Subsequently other workers have modified the design of the implant fixtures, abutments, surgical drills etc each with a view of overcoming certain shortcomings or lending certain extra benefits.