Osseointegration
From Wikipedia, the free encyclopedia
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 has enhanced the science of medical bone, and joint replacement techniques.
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[edit] Theories
Two theories regarding the chemical mechanism by which endo-steel implants integrate with bone have been proposed:
- Osseo-integration by Dr. Per-Ingvar Brånemark
- Fibro-osseous integration by Weiss
[edit] Branemark’s theory of osseo-integration
Branemark proposed that implants integrate such that the bone is laid very close to the implant without any intervening connective tissue. The titanium oxide becomes permanently fused with the bone, as Branemark showed in 1950s. Osseo-integration can be defined as,
- Osseous integration (1993) 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.
[edit] 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.
[edit] Osseointegration versus Biointegration
In 1985, 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. E.g. Commercially pure titanium and titanium alloys. In these cases, topological features like vents, slots, dimples, threads (screws) etc, aid in retention of the implant. There is no chemical bonding and the retention depends on the surface area. Greater the surface area, greater is the contact.
Bioactive retention can be achieved in cases where the implant is coated with bioactive materials like hydroxyapatite. These bioactive materials stimulate bone formation leading to a physico-chemical bond. The implant is ankylosed with the bone.
[edit] Links
it:Osteointegrazione pt:Osteointegração
