Lecture 17 Dental Implants (Slides)

8/3/2019 Lecture 17 Dental Implants (Slides)

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Dental implants

Dent 305


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Introduction Modern dental implantology is less than30 years old

Placement of a material into bonecreates a unique interface betweenimplant and body, so:

The implant material needs to bebiocompatible


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Implant components

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Important principles

Implant surgery involves careful and methodologicalsurgical technique to ensure minimal trauma andinflammation. Placing an implant involves: Bone removal with titanium alloy-slow speed

water-cooled burs Placement of implant and healing cap (6-8 weeks

healing) Re-open and placement of abutment caps Placement of abutments

Placement of crown or prosthesis


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Osseointegration

Osseointegration: refers to the lack ofintervening fibrous tissue and as littlespace as possible between bone and

metallic implant. This needs: Biocompatible implant materialAtraumatic surgical technique

This leads To almost no mobility(ankylosis)


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Biointegration Requires a chemical degradation of theimplant which favors bone formation

and is able to integrate with thesurrounding bone

Occurs in association with ceramic

implant materials


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Implant and force

Implant is used to restore esthetics andfunction Excessive forces on the implant intra-orally

may lead to failure Unlike natural teeth, occlusal forces are

directly transmitted to bone as compressive

forces leading to bone resorption Implants supported prosthesis are designed

to minimize excessive load


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Clinical considerations Clinical uses: early implants wereSubperiosteal or Transosteal.

Endosseous implants were not assuccessful due to lack of properosseointegration or biointegration.


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Continue, Implants maybe:

Single Multiple Maxillary Mandibular Support complete dentures Replace bridges and partial dentures


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Uses of implant


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Clinical success criteria

Osseointegrated or biointegrated interface No measurable mobility Implant is able to withstand forces over

time while maintaining integration Success rate maybe lower if:

Bone quantity or density is less Implant is loaded immediately

One step placement of implant


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Continue,

Implants are expected to last for 10years Ongoing horizontal bone loss is

expected (less than 0.5mm/yr) Horizontal bone loss greater than

0.5mm/yr or vertical bone loss indicatesfailure


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Clinical maintenance

Peri-implantitis: inflammatory processoccurring around implants due tomicroorganisms similar to those that

cause periodontitis. Maintaining good oral hygiene is

important (tooth brushing, flossing,scaling with plastic scalers and using

mild abrasives)


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Implant materials

Early material: Polymers: limited use due to lack ofosseointegration or biointegration, and lack

of strength. examples: Polymethylmethacrylates Polytetrafluoroethylene (Teflon)

Polyethylene Polysulfones polyurethanes


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Implant materials

Carbon based materials: have beenintroduced in several forms such as carbonsilicates, crystalline carbon forms. They

had low toxicity but the biological responseis not suitable for Endosseous implants.Also, they are brittle so, weak in tension


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Current materials

Pure titanium: Titanium (99% pure titanium, small

amounts of oxygen, traces of iron, carbon,

hydrogen and nitrogen. Amount of oxygenaffects strength and ductility.

The other trace elements affect strength,corrosion resistance and structure of thealloy


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Types and grades of titanium

alloys


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Continue,

Titanium alloys: similar to pure titanium,contains 6% aluminium and 4 % vanadium.These increase the tensile strength. Melting

range and modulus are similar tocommercially pure titanium.


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Continue,

To promote osseointegration, thesurface of the implant is coated withoxides of titanium and oxygen.

The oxide layer is 20-100 . Oxygenrich oxides are closer to the surface.

This layer should be free ofcontaminants


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Continue,

Trace elements from the implantmaterials maybe released into thesurrounding tissue and maybe found in

lungs, liver, spleen but no ill-effect hasbeen reported.


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Implant materials

Ceramics: Brittle: can withstand high compressive loads butlow tensile stresses.

High stiffness Inert Function well as Subperiosteal and Transosteal

implant Aluminum oxide based Zirconia based


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Ceramic coatings

On titanium alloy implants to promotebiointegration and strong implant-bonebonds. Combine strength of the

titanium alloy and biointegration. Thickness of the ceramic coating 50-

100 m


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Ceramic coating materials

Calcium phosphates: Hydroxyapatite (HA),tricalcium- phosphate (TCP): these can beused as ceramic coating materials

The more crystalline (less amorphous) thesematerial are, the more resistant to dissolutionthey become

Ion exchange between coating and tissueoccurs (some say that this might lead toweakening of the bond later).


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Ceramic coatings Even though ceramic coated implants

promote biointegration, some studies showedthat they were unstable and may lead to

bone damage Their rough surface may lead to plaque

accumulation and microorganisms

colonization Failures maybe caused by inflammation and

loss of the coating


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Criteria for selection of materials(ref. Phillip's science of dental materials)

Strength requirementsAvailability Implant design Bone height

Examples: for posterior implants,

strength is vital so the material ofchoice could be Titanium grade IV orany titanium alloy material


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Continue,

In some cases such as compromisedbone height, HA coated implants provedIn some studies to be more successful

than titanium implantsAnother indication for ceramic coated

implant materials is implantation infresh extraction sites (studies showedhigh success rates)


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Summary The performance and choice of appropriate

material is controversial Some studies show better performance for

one material over the other (short term andlong term) Other studies show no measurable difference

after certain time periods when titanium orceramic coated titanium is used.


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Summary The implant systems currently available are

diverse Despite the biocompatibility of the mentioned

implant material, the exact bone-bondingmechanisms are not fully understood When mechanisms that ensure stability and

bio-acceptance are fully understood, implantfailure will be rare


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Lecture 17 Dental Implants (Slides)