4th.
year class
Dental implant
Lecture 3
Factors affecting osseointegration
Osseointegration: The direct attachment or connection of osseus tissue
to an inert, alloplastic material without intervening connective tissue.
Factors affecting osseointegration:
1. Implant biocompatibility.
2. Implant design.
3. Implant surface.
4. Bone quality.
5. Surgical technique.
6. Loading condition.
1) Implant biocompatibility
A relationship exists between the material toxic reaction and a high
corrosion rate.
CO, Cu, Ni, V give rise to increased degradation in this order, and the degree
of toxicity is increased in the same order.
Metals that have corrosion passivation (high resistance to corrosion) do not
trigger a negative response of tissue, this behavior with Pt, Ta, Nb, Z r, & Ti.
The biocompatibility is affected:
1. Chemical composition.
2. Mechanical properties.
3. Electrical charge.
4. Surface features.
2) Implant design (root-form)
Commercial dental implants can be divided in to groups
according to:
A. Shape: cylindrical, conical, hybrid.
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B. Type pf connection: external hexagon, internal hexagon, Morse taper.
C. Surface treatment: acid etching, sandblasting, coated by plasma, sprays,
laser treatment.
D. Surface roughness: macro roughness, micro roughness nano roughness.
Cylindrical Implant
Some investigators explain the lack of bone steady state by over load
due to micro movement of the cylindrical design, whereas others incriminate
an inflammation/infection caused particularly by the very rough surfaces
typical for these types of implant.
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Threaded Implant
In contrast, threaded implants have demonstrated maintenance of a clear
steady state bone response.
To enhance initial stability and increase surface contact, most implant
forms have been developed as a serrated thread.
3) Implant surface
The number of threads per unit length, is an important factor in implant
osseointegration.
Increased depth between individual threads allows for improved contact area
between bone and implant.
Screw –shaped dental implants dominate the dentistry market. the screw
shape provides a large contact area between implant and bone , increases
primary stability , reduced the shear stress , in the bone – implant interface
,reduces the stress concentration in the cervical region .
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Surface treatment of titanium implants
1. Surface treatment of titanium implants
When the implant is blasted with silicon oxide, aluminum oxide,
titanium oxide.
2. Etching with strong acids: is another method for roughening
titanium dental implants ،the most commonly used solutions for acid
etching of titanium includes either a mixture of HNO3 and HF or a
mixture of HCl and H2SO4.
3. Sandblasted and acid-etched (SLA) implants :
This type of surface is produced by a large grit 250-500 µm blasting
process followed by etching with hydrochloric/sulfuric acid .Sandblasting
results in surface roughness and acid etching leads to Micro texture and
cleaning .These surfaces are known to have better bone integration as
compared to the above-stated methods.
4. Plasma sprayed surfaces: This process .consists in injecting
Titanium powders into a plasma torch at high temperature .The Titanium
particles are projected on to the surface of the implants where they
condense and fuse together ،forming a film about 30 µm thick, which
increases the surface area of the implant.
5. hydroxyapatite coating( HA ): hydroxyapatite coating has been
improved bone-implant attachment compared with machined surface. The
bone adjacent to such implants has been reported to be better organized
than with other implant materials and with a higher degree of
mineralization .The most common problem with such surface coatings is
the separation of coating from metallic substrate، a phenomenon known
as delamination .
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HA Coatings have the advantages of :
1. Increasing surface area.
2. Decreasing corrosion rates.
3. Accelerating bone formation via faster osteoblast differentiation.
4. Due to the enhanced bio mechanics HA coated implants are better able
to with stand loads.
5. More organized bone pattern and higher degree of mineralization at the
interface ،as well as ،increased bone penetration (which improve fixation).
4) Bone quality.
According to Lekholm 1985 bonequality divided in to:
Quality I
Was composed of homogenous compact bone usually found in the
anterior lower jaw.
Quality II
Had a thick layer of cortical bone surrounding dense trabecular bone,
usually found in the posterior lower jaw.
Quality III
Had a thin layer of cortical bone surrounding dense trabecular bone,
normally found in the anterior upper jaw but can also be seen in the
posterior lower jaw and the posterior upper jaw .
Quality IV
Had a very thin layer of cortical bone surrounding acore of low –
density trabecular bone, it is very soft bone and normally found in
the posterior upper jaw. It can also be seen in the anterior upper jaw.
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5) Surgical technique.
Minimal tissue violence at surgery is essential for proper osseointegration
1. Careful cooling while surgical drilling is performed at low rotatory
rates.
2. Use of sharp drills.
3. Use of graded series of drills.
4. The insertion torque should be of a moderate level because strong
insertion torques may result in stress concentrations around the implant,
with subsequent bone resorption.
6) Loading condition.
• Delayed loading:
1. Two- stage surgical protocol
2. One - stage surgical protocol
• Immediate loading :
1. Immediate occlusal loading (placed within 48 hours post-surgery).
2. Immediate non -occlusal loading (in single – tooth or short span
applications).
3. Early loading (prosthetic function within two months).
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