1. 1. Biologic Basis for Osseointegration
John Beumer III DDS, MS
Division of Advanced Prosthodontics, Biomaterials and
Hospital Dentistry, UCLA
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2. Implant
Osseointegration Surface
Definition – Direct structural
Bone
and functional contact between
ordered, living bone and the
surface of a load carrying
implant.
! Why is osseointegration such an important
development in implant dentistry?
! Predictability. For the first time replacement
of dentition with implants was very predictable.

3. Osseointegration
A radically new concept in implant dentistry
Why? What is so different about these
implants?
! Upon placement, bone is deposited on
the surface of the implant firmly anchoring
it in the surrounding bone.
! There is no fibrous connective tissue
interface between the surface of the
implant and the adjacent bone.
! As a result epithelial migration along this
interface is prevented

4. Osseointegration
*
Discovered by P. I. Branemark in the
1960’s while he was conducting a
series of animal experiments concerned
with wound healing in bone.
In these experiments
he used an optical
chamber made of
titanium. When he
attempted to remove
the chamber from its
bone site he noticed
that the bone adhered Bone
to the titanium chamber * *
Chamber *
with great tenacity. *Courtesy P.I. Branemark

5. Osseointegration - Early Work of Branemark
*
He immediately recognized the importance
of this phenomenon and during the next
several years he experimented with various
sizes and shapes including a design with
features of both subperiosteal and endoseal
implants. Over 50 designs were tested. He
and his colleagues finally settled on a simple
*
screw shape with a hex on the top.
* *Courtesy P.I. Branemark

6. Problems with previous implant systems
v Mostof the previous implant systems were made
of chrome-cobalt or similar alloys which were
subject to corrosion.
v Corrosion,with release of metallic ions into the
surrounding tissue, precipitated both acute and
chronic inflammatory responses resulting in
encapsulation of the implant with fibrous
connective tissue.
v Epithelial
migration, development of extended
peri-implant pockets, and chronic infections led to
exposure of the implant framework and its
eventual removal.

7. Subperiosteal Implants of Chrome Cobalt
v With the previous systems Implant Suspensory ligament of
immediately following placement Strut collagen fibers
the metal struts of the implants
became enveloped by fibrous
connective tissue.
v Upon occlusal loading the Bone
collagen fibers became oriented
to resist these forces and formed
a suspensory ligament (arrows). *
Implant
strut *Courtesy R. James
Note the ligamentous like attachment to bone (circle).
However, immediately after surgical placement the oral
epithelium begins to migrate along the interface between
the implant struts and the fibrous connective capsule.

8. Subperiosteal Implants - Method of Support
v Subperiosteal implants
evolved to take advantage of
this phenomenon
v The design was improved by
the addition of implant struts
parallel to the occlusal plane.
v These designs provided
more support for the occlusal
forces and prevented the
implant from being impacted
into the bone.

9. Subperiosteal Implants of Chrome Cobalt
Implant struts
The epithelial migration led to formation of extended
peri-implant pockets which in turn developed chronic
infections. These infections led to the exposure of
the implant struts and eventually loss of the implant.

10. Subperiosteal Implants of Chrome Cobalt
These infections were
particularly destructive of
bone in the maxillae.
In these two patients substantial portions of the hard palate were
lost secondary to infections caused by subperiosteal implants.

11. Uniqueness of Titanium
v Most metals are not suitable as biomaterials because of the
aforementioned corrosion and continuous release of metal
ions into adjacent tissues.
v The presence of these ions cause acute and chronic
inflammatory responses which eventually result in fibrous
encapsulation of the offending material and epithelial migration
then follows if the material extends through the skin or mucosa.
Titanium however is resistant to corrosion and spontaneously
forms a coating of titanium dioxide, which is stable,
biologically inert and promotes the deposition of a mineralized
bone matrix on its surface. In addition, it is strong, and easily
machined into useful shapes.

12. Uniqueness of Titanium
Properties of titanium - Summary
v Resistant to corrosion
v Spontaneously forms a coating of titanium
dioxide, which is stable, biologically inert
and with the proper surface topography
promotes the deposition of a mineralized
bone matrix on its surface.
v It
is strong, and easily machined into
useful shapes.

13. Osseointegration – Biologic Processes
v Blood clot formation, plasma proteins are attracted to
the area accompanied by the release of cytokines and
growth factors (BMP’s, VEGF etc)
v Angiogenesis
v Osteoprogenitor cell migration to the bone osteotomy
site and the surface of the implant
v Cell differentiation
v Deposition of bone on the surface of the implant
surface and the osteotomy site (Contact and distance
osteogenesis)
Completion of these processes on takes about from 8 weeks
to 4 months depending upon the implant surface.

14. Osseointegration – Clot Formation
v Bloodclot formation, plasma
protein adsorption
accompanied by the release of
cytokines and growth factors
(BMP’s, VEGF etc)
v The magnitude of plasma
protein adsorption (fibrinogen,
fibronectin, albumina and
others) is increased and
accelerated by the microrough
surfaces compared to the
machined surfaces
v Fibrin scaffold is created
v Angiogenesis begins

15. Osseointegration –Clot Formation
Platelets
v De-granulate and release mitogenic, chemo-
attractive and vasoactive factors
v Attracts stem cells onto the fibrin scaffold
Cytokines and growth factors

16. Osseointegration – Clot Formation
Fibrin Scaffold Develops
v Serves as a means of transit for
Implant stem cells as they migrate to the
surface surface of the implant and the
osteotomy site
v Plays a role in wound contraction
through the action of fibroblasts
v Micro-rough surfaces appear to
better retain and maintain the fibrin
scaffold structure better than
machined surfaces
l Clot retraction especially seen with
machined surfaces

17. Migration and Differentiation of
Mesenchymal Stem Cells
Functioning osteoblast
v Stem cells migrate to the implant surface and
into the osteotomy site via the fibrin network
v The micro-rough facilitates clot retention and cell
migration

18. Osseointegration – Osseous Healing
Osteotomy Site
Distance osteogenesis
• Ingrowth of bone from the lateral wall
of the ostetomy site Implant
Surface
Contact osteogenesis
• Implant surface acts as a site for
colonization and differentiation of
osteoprogenitor cells followed by the
deposition of bone

19. Osseointegration – Biologic Processes
Oseous Healing
v Micro-rough surfaces
facilitate and promote
contact osteogenesis
v The new surface
topographies increase the
rate of contact
osteogenesis on the
implant surface

20. Osseointegration – Remodeling
v Process
where Osteoid
preexisting woven, Mineral
Osteoclasts
damaged and necrotic
bone is removed and TGF-β, OP-1
replaced with new bone
through the actions of a Source:
Lynch, Genco and Marx.
basic multicellular unit Tissue Engineering 1999
(BMU).
v Necessary to maintain bone anchorage during
functional loading during the life of the implant

21. The Bone-Titanium Implant Interface
* This interfacial
zone of bone
Titanium layer
Implant matrix proteins is
surface
similar to the
material found in
the “cement lines”
Titanium dioxide between layers of
layer * Bone bone.
Surface film of complex phosphates of
titanium and calcium
Noncollagenous bone matrix proteins
(osteopontin, osteocalcin and bone
sialoprotein, ie cement line)
Mineralized bone matrix
*Courtesy of M. Weinlander

22. Titanium – Epithelial Interface
What is the mechanism of Sulcus
Implant Surface
attachment? Epithelium
v Hemi-desmosomal –
basal lamina system
*
Circumferential
collagen fibers
Bone
Hemi-desmosomes
*Courtesy P. I. Branemark

23. Titanium – Epithelial Interface
Sulcus Epithelium
Implant Surface
Biologic width
phenomenon
3 - 4 mm
l Similar to that found in
natural dentition
l Generally 3-4mm
l Significant impact on
bone levels and Circumferential
therefore esthetics in collagen fibers
the anterior region
Bone
*

24. Prerequisites for Achieving Osseointegration
v Uncontaminated implant
surfaces
v Creation
of congruent, non-
traumatized implant sites
v Primary implant stability
v Norelative movement of
the implant during the
healing phase

25. Uncontaminated Implant Surfaces
Bioreactivity of the implant surface is
impaired if it becomes contaminated
with organic molecules
! The surface charge is changed from
positive to negative
! The surface becomes less wetable

26. Uncontaminated Implant Surfaces
Light-treated acid-etched surface!
*p<0.0001
Original! Light! N=4
100
*
80
*
60
40
20
0
Day 14! Day 28!
Bone–implant contact!

27. Prerequisites for Achieving Osseointegration
Creation of congruent, non-traumatized implant sites
Careful preparation of the implant site is critical to obtaining a
state of osseointegration between implant fixture and bone.
During surgical preparation of the site, bone temperatures above
47 degrees centigrade create necrotic bone and lead to impaired
healing and increased likelihood of a connective tissue interface
forming between the implant fixture and the bone.

28. Prerequisites for Achieving Osseointegration
Congruent implant sites
v The smaller the gap between the osteotomy site and the implant
surface the better
v For osseointegration to occur the gaps that exist between the bone
and the surface of the implant are initially filled with blood clot and if
the gap is too large the clot may become detached
v The bone adjacent to the site may also be damaged (over heated)
during surgery.
v In an ideal situation, these gaps are small (less than 1 mm), the
amount of damaged bone created during surgical preparation of the
bone site is minimal, and the implant remains immobilized during the
period of repair.
v Under these circumstances the implant becomes osseointegrated a
very high percentage of the time (95% or greater with the modern
implant surfaces).

29. Prerequisites for Achieving Osseointegration
Congruent, nontraumatized site preparation
v In this patient the coronal portion of the
bone site was either overheated over-
prepared.
v The apical portion of the implant is
osseointegrated but the upper half of the
implant is encapsulated in fibrous
connective tissue.
v Epithelial migration will likely lead to formation of
deep peri-implant pockets, chronic infections
and loss of the implant.
So-called wide body implants (6mm diameter) have a lower success
rate (80% vs 97%) than the traditional 4mm diameter implants
probably because it is more difficult to prepare the osteotomy site.

30. Prerequisites for Achieving Osseointegration
Wall of osteotomy
Congruent, site
preparation Old
bone New bone
With the new surfaces
the gaps between the
implant surface and the
osteotomy site can be up
to two mm and still fill in
with bone if primary
immobilization of the
implant is achieved and
maintained.

31. Prerequisites for Achieving Osseointegration
Primary implant stability
Submerged Implants
Micromovement is thought to disturb the tissue and vascular structures
necessary for initial bone healing. Davies (1994) suggested that excessive
micromotion of the implant during healing prevents the fibrin clot from
adhering to the implant surface. Eventually, the healing processes are
reprogrammed leading to a connective tissue interface as opposed to a
bone implant interface.

32. Prerequisites for Achieving Osseointegration
Absence of micromotion during the healing period
Immediately following placement the
bone implant appositional index is
approximately 10-15% even in
favorable bone sites such as the
anterior mandible. If the implant is
subjected to occlusal load at this point
and mobilized, a fibrous connective
tissue encapsulation results.
It takes 2-4 months to repair the trauma secondary to
preparation of the implant site and develop sufficient bone
anchorage to withstand occlusal loads without provoking a
resorption remodeling response of the investing bone.

33. Prerequisites for Achieving Osseointegration
Factors leading to fibrous encapsulation and
failure to achieve osseointegration
! Overpreparation of the site – gap between the bone
and the surface of the implant is too large
• Machined surfaces vs micro-rough surfaces
! Overheating the site – the necrotic bone produced
must be phagocytized before healing and
deposition of new bone can occur
! Micromotion of the implant during the healing phase
• Immediate loading?
! Contamination of the implant surface prior to
placement

34. Progressive Osseointegration
Following initial healing (4-6 months)
the bone appositional index (amount
of bone contact with the surface of
the implant) continues to increase to
where it approaches almost 90% in
favorable sites (such as the anterior
mandible when bicortical anchorage
is achieved during surgical
placement). In most bone sites the
index varies from 35-70%. The
index is highest in the anterior
mandible and lowest in the posterior
maxilla

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