OSSEOINTEGRATION v/s FIBRO-OSSEOS INTEGRATION

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Two theories regarding the chemical mechanism by which endosteal implants integrate with bone have been proposed. Osseointegration, as defined above. That type of integration contrasts with fibrosseous integration, in which soft tissues such as fibers and/or cells are interposed between the two surfaces.
Brånemark’s theory of osseointegration
Brånemark 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 Brånemark showed in 1950s.
[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, 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.
Technique

For osseointegrated Dental implants, metallic, ceramic, and polymeric materials have been used,[2] in particular titanium.[10] To be termed osseointegration the connection between the os and the implant need not be 100 percent, and the essence of osseointegration derives more from the stability of the fixation than the degree of contact in histologic terms. In short it represents a process whereby clinically asymptomatic rigid fixation of alloplastic materials is achieved, and maintained, in bone during functional loading.[11] When osseointegration occurs, the implant is tightly held in place by the bone. The process typically takes several weeks or months to occur which is well enough for the implant dentist to complete the restorations. The fact is that the degree of osseointegration of implants is a matter of time. First evidence of integration occurs after a few weeks, while more robust connection is progressively effected over the next months or years.Though the osseointegrated interface becomes resistant to external shocks over time, it may be damaged by prolonged adverse stimuli and overload, which may result in implant failure. In studies performed using 3M™ ESPE™ MDI Mini dental implants, it was noted that the absence of micromotion at the bone-implant interface was necessary to enable proper osseointegration.Further, it was noted that there is a critical threshold of micromotion above which a fibrous encapsulation process occurs, rather than osseointegration. Already Brånemark stated that the implant should not be loaded and left out of function during the healing period for osseous integration to occur.
Other complications may arise even in the absence of external impact. One issue is the growing of cement.In normal cases, the absence of cementum on the implant surface prevents the attachment of collagen fibers. This is normally the case due to the absence of cementum progenitor cells in the area receiving the implant. However, when such cells are present, cement may form on or around the implant surface, and a functional collagen attachment may attach to it.
]Advances in materials engineering: metal foams
Since 2005, a number of orthopedic device manufacturers have introduced products that feature porous metal construction Clinical studies on mammals have shown that porous metals, such as titanium foam, may allow the formation of vascular systems within the porous area. For orthopedic uses, metals such as tantalum or titanium are often used, as these metals exhibit high tensile strength and corrosion resistance with excellent biocompatibility.
The process of osseointegration in metal foams is similar to that in bone grafts. The porous bone-like properties of the metal foam contribute to extensive bone infiltration, allowing osteoblast activity to take place. In addition, the porous structure allows for soft tissue adherence and vascularization within the implant. These materials are currently deployed in hip replacement, knee replacement and dental implant surgeries.