Lecture 17, Dental Implants (Script)

8/3/2019 Lecture 17, Dental Implants (Script)

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Dental Implants

Dental Material II Lecture # 17

* What are the Implants?

They are mainly a type of restoration that is used to replace a missing tooth or a number of

teeth. So you can either use it after extraction of one tooth or two teeth or the entire

dentition. And you want something to fit your restoration in place, so can place a crown on

top of it, a bridge, a complete denture or a partial denture.

It's a relatively new type of restoration, so it's a thirty or a forty-year old type.

So researches are always going on the implants to try and to get the success rate over

decades or a number of years.

This material (the implants) is placed in living tissue (inside bone), so the most importantrequirement is the biocompatibility of this material.

A hole is drilled in the bone and this implant is placed inside so it's going to be part of the

body. So it has to be highly biocompatible or inert and does not cause any irritation or side

effects on the local tissue or the entire system of the human being.

===========================================================================* The parts of the implant. It's mainly composed of 3 parts:

A – The fixture (endosteal root form): the part which goes through

the bone

B – The abutment: the part which is going to support the restoration

C – The actual prosthesis: crown, complete denture, partial denture.

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* Implants Principles:

Before Placement of the implants, we take a radiograph to know the quality of bone, is

there enough bone, thickness and length to place the implant. If the quality of bone is good

to support the implant and the restoration on top, the surgeon will:

1 – Drill a hole in the bone using a titanium alloy- slow speed water-cooled burs.

2- Fix the implants their, and allow it to heal for a few weeks.

3- re-open and placement of abutment caps.

4- Placement of the abutments.

5- Placement of crown or prosthesis.

The important thing about this procedure is that it is a team-effort, so it's done by the co-

operation between the surgeon and the prosthodontist.

In picture (A), the wound is exposed and you can see the upper part of the implants, tissue

are allowed to heal in (B) , in (C) these are the abutment on which the crown will be placed

And then the crown is placed as in (D). So it's a multi-step procedure.

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Some schools or some people say that we can immediately place a load on these implants

before allowing the tissue to heal. And placing a load will even promote more healing.

So it's a debatable issue, but I believe most likely to have tissue healing before actually

loading the implants or allow it to do its function.

===========================================================================

To achieve this unique relationship between the implants and bone, one of two things

might happen (depends on the material of the implant):

1- Osseointegration: there will be very minimal

space between bone and implant (there is no fibrous tissue,there is no PDL), and it's 100 A° (10-10 meter). But it has no

mobility (ankylosis).

This needs to:

1- Biocompatible implant material

2- Atraumatic surgical technique (no trauma or inflammation or contamination)

2- Biointegration: the surface of the implant has a

certain amount of specific material lined on top of it; it can

immediately contact the bone so there will be no space at all.

The surface has some calcium and phosphate material on top of it (same materials that

present in bone), so bone tissue will actually attach to it, this will lead to biointegration.

This requires degradation of the implants, that's mean your implant has a material on its

surface that's going to interact with the bone around it; this will lead to bone deposition

and ion exchange between the implant surface and the bone. This source of reaction will

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cause bone formation directly on the surface of the implant which leads to

biointegration.

* Both lead to successful result, only due to the difference in the material at the surface of the implants *

===========================================================================

Implants can be used to support several type of restoration, but Excessive force can lead to

failure. Because in the natural tooth you have the periodontal tissue which transmitted the

force in a favorable way to the bone in order to prevent bone resorption.

In case of the implant, there is no PDL, no periodontal tissue, and no fluid. This might lead

to direct transmission of the force to the bone which can lead to bone resorption. That's

why the design of your implant or restoration is important; you need to minimize the

amount of force, by increasing the surface area of your restoration for example.

===========================================================================

* Types of Implants

We have 3 types of implants:

A. Subperiosteal : the implants framework is placed

underneath the periostueom

B. Transosteal: the implants framework is placed all the

way through the thickness of the bone from top to bottom.

C. Endosseous: implants framework is placed inside the

bone. It's the most current one and the most commonly used

now. The success rate is much higher and the technique is less traumatic.

===========================================================================

* Implants maybe:

A – Single

B – Multiple

C – Maxillary

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D – Mandibular

E – It can support any type of restoration (depends on the clinical situation)

For example, this is a radiograph showing theimplant inside bone. Here is the abutment that

appears intra-orally, and on top of it the crown is

going to be placed.

So in this case the implant is supporting the

central incisor. So instead of doing a bridge where

you need to drill or prepare the teeth on both sideof the extraction side, you only need to do the implant. So it's more conservative but on the

other hand it's much more expensive.

In other cases, multiple implants are placed to

support a complete denture. Need four to implants

to support it, which will provide good retention and

stability of the denture.

This is a picture of a special tooth brush that's used

to clean underneath the denture. Certain type of

toothbrushes is necessary to maintain a good oral hygiene. It's very important because as

we have peridonititis, there's something called Peri-implantitis (inflammation of the tissue

around the implants).

===========================================================================

* What are the factors that tell you that the procedure has succeeded or the implants are

successful?

1 – No measurable mobility.

2- Good Osseointegrated and biointegrated, which can be partially seen in a

radiograph.

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3- The implant should be able to withstand any force that is subjected to without

mobility.

===========================================================================

* What are the factors that can make a low success rate?1- Irritation or trauma or contamination during the procedure.

2- The bone quality or quantity is not very good.

3- One step placement of the implants ( without a tissue-healing period )

===========================================================================

Q. Can the implants prevent bone resorption?

A. No.

* Implants are expected to last for 10 years

* The bone resorption is a normal process as the patient gets older. The normal rate of the

Ongoing horizontal bone loss is expected (less than 0.5mm/yr). But if it goes beyond that

or it goes vertically, then it indicates a failure of the implants.

* Peri-implantitis: inflammatory process occurring around implants due to microorganisms

similar to those that cause periodontitis.

* Maintaining good oral hygiene is important (tooth brushing, flossing, scaling with plastic

scalers and using mild abrasives).

===========================================================================

* Implants materials:

1- Early material (the older material): it has many disadvantages by

being weak, brittle and cause irritation.

A – Polymers: limited use due to lack of Osseointegration or

Biointegration, and lack of strength.

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Such as:

1- Polymethylmethacrylates

2- Polytetrafluoroethylene (Teflon)

3- Polyethylene

4- Polysulfones

5- Polyurethanes

B- Carbon based material: they have low toxicity but the

problem that's they are too weak and brittle.

2- Current material: are mainly based on titanium. It's a highly

biocompatible material and does not cause any irritation of the soft tissue

or the hard tissue around it.

It could be used pure, but it's better to use it as alloy, because the alloy isstronger than the pure metal.

- Pure titanium: it's 99% pure titanium. It's mixed with a small

amount of oxygen, iron and carbon. All of these elements can

improve properties of the metal.

- Alloy titanium: they alloy it with other material or increase the

amount of some materials.

In this case we add aluminum (6%) and vanadium (4%)

(Melting range and modulus are similar to commercially pure

titanium).

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* Here we have 4 types of the pure titanium but different amount with oxygen; this will

affect the strength and the ductility (قرطلا ةيب) of the material.

* The strongest is grade 4 and the weakest (more flexible) is grade 1.

* We also have the alloys which are even stronger.

So if you want something to support a multi unit bridge or in the posterior area of the

crown, you need an alloy. So it depends on the clinical situation.

In cases of these metallic implants they need to have a certain surface layer that's rich in

oxygen for example or in oxide which will promote a good bonding between the implantsand the bone around it, and prevent the mobility of the implant.

This layer is 20-100 Å. Oxygen rich oxides are closer to the surface and it should be clean

(free of contaminants and bacteria).

* Trace elements from the implant materials maybe released into the surrounding tissue

and maybe found in lungs, liver, spleen but no ill-effect has been reported.

Another type of the implant material is based on ceramics. The good things about

ceramics:

1- Brittle: can withstand high compressive loads but low tensile stresses.

2- High stiffness

3- Inert

4- Function well as Subperiosteal and Transosteal implant

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5- Aluminum oxide based

6- Zirconia based

Now instead of using an implant that's made out of ceramics, they make advantage of this

ceramic material by making it as a liner ( a surface layer on top of the implants ) to

enhance biointegration .

So you got the implant made of titanium alloy, and on the surface there is a layer made out

of a ceramic material or calcium phosphate material.

Now when the implantation is done, ion exchange will occur between the implants and thesurface of the bone which will improve the deposition of calcium and phosphate and bone

formation and intimate contact between the implants and bone.

The thickness of this ceramic layer has to be between 50 – 100 μm.

But there are problems associated with this material; it can become rough with time due to

degradation, so this will promote bacteria colonization which can lead to inflammation andfailure. So sometimes with time this surface layer may become detached from the implant

itself, so delaminating can occur which may lead to more failure.

The coating on the surface can be made out of several

materials such as Hydroxyapatite, tricalcium- phosphate.

All of these can be used as lining material or surface layer material. If the material is more crystalline (less

amorphous) it becomes more resistant to dissolution

(stronger).

this is a represtation to the surface layer that's composed of

tricalcium-phosphate (regaredless of what it is) and this is an example of failuer that might

occur because the surface layer was deattached from the implant surface.

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which means that the benfits of the surface material will be lost because it was seperated

from the implnats .

===========================================================================

* How do you select your implant material?1 – Availability of the implants material around you

2- The strength requirements

3- The quality of bone that you got

4 – The Implant and restoration design

For example, if you need to restore something in the posterior part of the mouth (wherethere is high load) you need for example titanium alloyed or grade (4) titanium.

if got an implant that you have to place it in a freshly extraction socket, which means that

you extracted the tooth and you want to immediately place the implant there you want

something to promote bone formation quickly, so an implant that is lined with ceramics

might be a good choice.

And that's it…Thank you

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Forgive Me For Any Mistake And Sorry For Being Late.

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Yazeed,,ah Karaki,,,mabsso6 ?!!?

Rafay3a,,,9'al fee lab Prostho aw Cons ma 3awa9'to !!!

If you have 3 words, Mine are unlimted,,,, 7ayeoo ;)

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Done By: Laith Jamal

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Lecture 17, Dental Implants (Script)

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