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Osseointegration is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant, typically made of titanium. It is a property virtually unique to titanium and hydroxylapatite, and has enhanced the science of medical bone, and joint replacement techniques.
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History
In 1952, Prof. Per-Ingvar Branemark of Sweden conducted an experiment where he utilized a titanium implant chamber to study blood flow in rabbit bone. At the conclusion of the experiment, when it became time to remove the titanium chambers from the bone, he discovered that the bone had integrated so completely with the implant that the chamber could not be removed. Branemark called the discovery "osseointegration," and saw the possibilities for human use. The procedure was first implemented in dentistry for fixation of teeth and now also is used for cranial and maxillofacial reconstruction as well.
Applications
- Dental implants
- Retention of a craniofacial prosthesis such as an artificial ear (ear prosthesis), eye (orbital prosthesis), or nose (nose prosthesis)
- Bone anchored hearing conduction amplification (Bone Anchored Hearing Aid)
Theories
Two theories regarding the chemical mechanism by which endosteal implants integrate with bone have been proposed:
- Osseointegration by Dr. Per-Ingvar Brånemark
- Fibro-osseous integration by Dr. A. Weiss
Branemark’s theory of osseointegration
Branemark proposed that implants integrate such that the bone is laid very close to the implant without any intervening connective tissue. The titanium oxide permanently fuses with the bone, as Branemark showed in 1950s. Osseointegration can be defined as,
- Osseous integration, the apparent direct attachment or connection of osseous tissue to an inert alloplastic material without intervening connective tissue.
- The process and resultant apparent direct connection of the endogenous material surface and the host bone tissues without intervening connective tissue.
- The interface between alloplastic material and bone.
Branemark also stated that the implant should not be loaded and left out of function during the healing period for osseous integration to occur.
Weiss' theory of fibro-osseous integration
Weiss' theory states that there is a fibro-osseous ligament formed between the implant and the bone and this ligament can be considered as the equivalent of the periodontal ligament found in the gomphosis. He defends the presence of collagen fibres at the bone-implant interface. He interpreted it as the peri-implantal ligament with an osteogenic effect. He advocates the early loading of the implant.
Osseointegration versus Biointegration
In 1985, Dr. C. de Putter proposed two ways of implant anchorage or retention as mechanical and bioactive. Mechanical retention can be achieved in cases where the implant material is a metal, for example, commercially pure titanium and titanium alloys. In these cases, topological features like vents, slots, dimples, threads (screws), etc. aid in the retention of the implant. There is no chemical bonding and the retention depends on the surface area: the greater the surface area, the greater the contact.
Bioactive retention can be achieved in cases where the implant is coated with bioactive materials such as hydroxyapatite. These bioactive materials stimulate bone formation leading to a physico-chemical bond. The implant is ankylosed with the bone.
See also
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- This page was last modified on 3 September 2008, at 00:13.
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