Cons (Adhesive System)

8/13/2019 Cons (Adhesive System)

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Adhesion:attachment of one substance to another.

Adhesive system (bonding agent): 2 materials or 2 surfaces and you apply a material in

between which can:

Join the 2 materials or surfaces together.

Persist their separation.

___?Capacity (00:00:35) :: will act like shock absorber by strength the link between

teeth structure.

Requirement of adhesion:

Intimate contact between the 2 surfaces.

Sufficient wettability:

Angle forming between the droplet and the surface:

Smaller the angle better spreading better, wettability

Good surface energy to absorb and make the droplet flow.

High surface energy ,low tension:

The surface is hydrophilic which mean it loves water.


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Poor wetting high contact angle+ low surface energy.

Good wettinglow contact angle+ high surface energy.

Perfect wetting the angle equal zero.

Which is better adhesion to enamel or dentine?

Enamel: better and much easier because it has higher surface energy.

It contains more inorganic material (hydroxyapatite crystals) high surface energy).

On the other side, Dentine composes of inorganic (hydroxyapatite) +organic (collagen)

lower surface energy than enamel.


3/12

In the oral environment we have organic pollutants like the saliva, proteins... Etc.

Which has Low surface tension; it will impair the adhesion as

well, and decrease the bond and compromise the adhesion to the tooth structure.

Smear layer:

Calcific debris formed within instrumentation and preparation of the tooth, they have

low surface energy as well.

So we have 2 problems:

One related to teeth structure:: Dentine which has low surface tension.

The other related to the smear layer we produced within instrumentation.

Both will compromise the bond.


4/12

I have to have an isolated field and clean tooth which should to conditioned by applying

acid etching.

You apply acid etching to modify teeth structure and the smear layer after isolation and

cleaning the tooth.

Dr. Michael Buonocore has best credit for adhesive dentistry. He suggested and did

many studies about the effect of acid etching on tooth structure.

If we have Very good bonding it will improve your work (long standing restorations (good

durability)).

Adhesive technique advantages:

Conservative and preservation of tooth structure: we dont remove a lot

from the tooth structure.

Homogeneous distribution of tensions throughout the union allowing the

elimination of stress concentrations.

Esthetic: like veneers.

Reduce micro leakage.

Easier to repair.

What are the subsequences of reducing micro-leakage?

Improving the postoperative sensitivity.

Decrease marginal staining.

Decrease recurrent caries.

What are the indications of adhesive dentistry?

Restoration of carious and fractured teeth.

Correction of shape, position, size and color (veneers like composite or

porcelain).

Core builds up.

Extra coronal restoration like onlay, crowns and veneers.


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Orthodontics and periodontal splints.

Orthodontics bands.

Dental hypersensitivity.

Repair fractured composite.

Pit and fissure sealant.

Bonding to amalgam restorations.

Bonding agent:low viscosity material thats applied to the tooth surface (thin film

thick layer will affect the bond appears in radiograph as radiolucent line underneath

that will induce recurrent caries).

Dont spread it with air only by brush.

After applying, you have to light cure it for 20 seconds.

Bi-functional molecule which will attach to the teeth surface and resin

Low viscosity resin attaches to micro porosity created by the reaction.

Major role is to stabilize the hybrid layer.

Resin tags: resin extensions closer to composite resin, formed inside micro porosity,

when the bonding agent penetrates the resin tags the composite will hold!!

To have an interlocking bond(good bonding strength) you should have:

Good isolation

Good etching

Good bonding

Enamel bonding: micromechanical.

Dentine bonding: micromechanical+ chemical.


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Ideal properties of bonding agent:

Biocompatible.

Low film thickness.

Low viscosity.

Strong bond.

Good dimensional stability.

Good shelf life.

Compatible coefficient of thermal expansion??( The cte of the restoration should be

similar to that of the tooth .. So when the pt drink cold water for eg the restration and

the tooth will shrink in the same rate or when he drink hot drinks both will expand inthe same manner so there'll be no microleakage nore fractures of the tooth due to the

pressure from the restoeation )

Clinical steps for bonding:

Proper isolation and

Pulp protection in deep cavities.

Etching, inorganic acid phosphoric acid 37%\\ the gel is better bcz its easier to

manipulate .liquid will dry easily

primer

adhesive

Acid etching:Application of chemical (acid etching) to alter the surface configuration.

(Hydroxyapatite and smear layer modification)

Purpose of acid etching:


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Protection of substrate that capable of micromechanical: prepare the tooth structure to

receive the bonding and restoration by changing the micro structure of enamel, dentine

and smear layer.

We accomplish two goals by etching the dentin. First we remove the smear layer anddebris present from tooth preparation. The dentinal tubules become clogged with cut

tooth structure, saliva, red blood cells and other contaminates like oil from our hand

piece. The etching process effectively removes all of this to expose open dentinal

tubules which can be filled with resin. Secondly, the acid etch demineralizes a layer of

the dentin, exposing the collagen fibers, allowing the resin to penetrate into the dentin

structure. We carefully manage the chemicals and timing during etching (total etchor

self-etch) in order to effectively remove the smear layer, open the tubules and create

an adequate demineralized zone that resin can infiltrate.

Again, the Smear layer is calcific debris formed within instrumentation and preparation

of the tooth; they have low surface energy as well.

Benefits of smear layer:

Reduces dentinal permeability.

Limits out flow of pulpal fluid

Natural barrier to the pulp.
http://leeannbrady.com/restorative-dentistry/restorative-techniques/total-etch-technique-dentinhttp://leeannbrady.com/restorative-dentistry/restorative-techniques/total-etch-technique-dentinhttp://leeannbrady.com/restorative-dentistry/restorative-techniques/total-etch-technique-dentinhttp://leeannbrady.com/restorative-dentistry/restorative-techniques/total-etch-technique-dentin


8/12

Etched enamel:dissolved hydroxyapatite crystals give new micro structure like honey

camp

Average of penetration: 10-25

Enamel surface etched with 35% and 10% phosphoric acid gels for 15

and 60 seconds. Areas with preferential removal of prism core material and the prism

peripheries relatively intact

Clinical description of etched enamel: frosty.

Factors effecting acid etching of enamel:

Types of acids(phosphoric acid 37%, inorganic)

Duration (15 seconds). The prisms (bevel: you expose more surface area to enhance the bond).


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Un-etched enamel (left), etched enamel at 500x magnification (middle), etched enamel at

5000x magnification (right).

Etched dentine: dissolution of the smear layer and demineralizing dental surface

Changing the micro structure, u will be able to see the collagen fibers. The collagen

fibers will remain.


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Dentinal surface etched with 35% phosphoric acid gel for 15 and 60 seconds. The acid has removed

the smear layer and opened the dentinal tubule orifices.

Etched and un-etched dentin (500x) (left),

Etched dentin (500x) (smear layer removed) (right).

Shrinkage of collagen fibers within the dentin caused by over drying during acid - etch procedure (E:

acid-etched dentin, W: water)

Over drying will cause collagen collapse so there wont be enough spacefor the resin tags. So avoid

over drying.


11/12

The hydrodynamic theory:the mechanism by which atoothperceives

sensation. It states that the flow of fluid in dentinal tubules trigger receptors within the

tooth. It is the most widely accepted theory explaining tooth sensitivity
http://en.wikipedia.org/wiki/Toothhttp://en.wikipedia.org/wiki/Toothhttp://en.wikipedia.org/wiki/Toothhttp://en.wikipedia.org/wiki/Tooth


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Cutting in tooth structure will cause Vibration it will move the dentinal fluid toward the

pulp stimulating the nerve ending, thats why after each operation and when u reach

dentine you have to inform your patients that the might have sensitivity because of this

.

The end

Done by: Amal Ameer

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Cons (Adhesive System)