We can begin this presentation by asking the question
“What is Osseointegration?"
There've been several definitions for osseointegration,
but a commonly used one is a direct, structural
and functional connection between ordered, living bone
and the surface of a load-carrying implant.
Direct bone-to-implant contact was first described
by Branemark in 1969
and histologically demonstrated by Schroeder
as functional ankylosis.
When an osteotomy is prepared,
a wound healing cascade is initiated
which can be broadly divided into three overlapping phases:
inflammation, matrix formation, and remodelling.
These phases are common to all healing
and involve a large range of cells and molecules,
as can be seen on this slide.
Now the key events that lead to osseointegration
occur at the implant surface, interface.
There are a number of different processes that take place
and these are relatively complex.
The first phase of healing following implant placement
into the freshly prepared osteotomy
involves the formation of a blood clot.
Initially, there is adsorption and desorption of proteins
on the implant surface.
At the same time an inflammatory cascade is initiated
and the surface of the implant undergoes changes
as it interacts with the blood clot.
In the following days, the coagulum is replaced
by tissue rich in mesenchymal cells,
which will ultimately form the future osteoblasts.
These cells enter through the surrounding vasculature,
as well as the surrounding bone tissue.
We also see signs of the formation of blood vessels.
And furthermore, osteoclasts can be seen
on the surgical edges of the osteotomy
as the damaged bone is remodelled.
In the following weeks, we start to see the signs
of mineralized matrix formation
as the first step towards the formation of a bone matrix.
Intramembranous bone formation
leads to the formation of immature woven bone.
This woven bone is ultimately remodelled into lameller bone
in the following months
via the co-ordinated action of osteoblasts and osteoclasts.
Based on histological observation
at the bone-implant interface,
there are two proposed mechanisms of osseointegration.
The first is called distance osteogenesis.
This is where a new bone is formed
on the surface of existing bone
on the edges of the surgically created osteotomy.
In these cases, bone is laid down by opposition.
The second proposed mechanism
is called contact osteogenesis.
This is where bone cells migrate directly
onto the implant surface.
They differentiate and produce a bone matrix,
which then matures into a bone
which is in direct contact with the implant.
An important consideration
is also the establishment of soft tissue integration
which in many ways is very similar
between implants and teeth.
However, there are some important differences.
Firstly, fibers around implants are parallel
rather than perpendicular to the surface of the implant.
The connective tissue surrounding the implant
is also far less vascular than that found around teeth.
Finally, we need to consider the factors
that can affect the osseointegration process.
This can be broadly divided into three categories.
These are implant, operator, and patient related factors.
In that implant category,
we need to consider the material that is used,
with commercially pure titanium being well-established
as having the ability to support osseointegration.
Then, we also have the macro level features of the implant,
as well as, the micro topography of the implant surface
which can both affect the osseointegration process.
Then we have the operator level factors.
These are usually related
to the surgical technique being used
with aseptic technique being essential,
as well as, adequate irrigation
to ensure that the osteotomy site is not overheated.
Finally, there is the patient related factors.
These relate to both the site
meaning that the quality and quantity of bone
is to be adequate for implant placement.
Furthermore, the systemic health of the patient
needs to be sufficient to support
the osseointegration process.
And factors, such as uncontrolled diabetes
and severe osteoporosis may
compromise the osseointegration process.