Zr Dentin and Enamel Bonding

8/3/2019 Zr Dentin and Enamel Bonding

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Thomas J. Boyle, DMD, MAGD, ABGDDiplomate of the American Board of General Dentistry

TJB


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TJB


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Smear Layer

(produced by diamond ondentin)

TJB


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Smear Layer

Dentinal surface andtubules areobstructed. Shattered and crushed

hydroxyapatite,fragmented anddenatured collagen,bacteria? And saliva.

Some degree of

etching is required toovercome thisobstacle

TJB


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Dealing with the Smear

Layer

TJB


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Classification ofAdhesives

4th 5th 6th th

HEMAhydrophylic

Bis-GMAhydrophobic

TJB

Etch


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Brand Names of AdhesiveSystems

3-E&R

2-E&R

2-SEA

1-SEA

TJB


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3 step-E&R Systems

TJB

4th gen


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2 step-E&R Systems

TJB

5thgen


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2-SEA systems

TJB

6th gen


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1-SEA Systems

TJB

7th gen


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Hybridization

Hybridization is the commonadhesion mechanism ofall systems(E&R and SEA).


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Hybrid Layer Achieved

by:

TJB


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Etch and Rinse Technique vs. SelfEtch

enamel/resin interface

TJB


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Dentin Bond

Phosphoric Acid 35% Removes Smear Layer

Demineralizes dentin to depth

of 3.0m to 5.0 m. Exposes a scaffold of collagen

fibrils nearly depleted ofhydroxyapatite.

Monomers diffuse into thenetwork of collagen fibrils and

set to form hybrid layer. Chemical rxn between collagen

and MMA is unlikely

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. Note that collagen fibrilsmust notbe allowed to

collapse. Loose the micromechanical

retention.

Collagen fibrils are inert(s HAp) and monomers

have low affinity tothem. Therefore nanometer-sized

gaps are left that leak andgradually deteriorate thebond.

Water Trees

TJB


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Primer Solvents

TJB


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New Three Step Technique

TJB


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Self Etch Systems

TJB


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TJB


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TJB

Variable/Unpredictable Bond Strengths with SEAsvs. E&Rs

Despite the thin hybrid layer and lack ofresin tags- some Mild SEAs can achievea satisfactory bond strength. Probably due to additional chemical rxn

between monomers and residual HAp.

(Mild SEAs leave HAp)

However : {Tooth- SEA } chemicalinteractions are highly variable. They depend on the kind of acidic functional

monomer and on the overall composition ofthe monomer.


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TJB

The carboxylic and phosphate groups that renderthese monomers hydrophilic and that function asproton donors (acid etchants) have been provento bond ionically with the calcium inhydroxyapatite.

So the mild SEAs get some bond strength (not

as much as E&Rs) because they leave some HAp

The chemical bond is monomer specific anddepends on the hydrolytic stability of thecalcium-monomer bond. So why use SEAs?


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TJB

SEA Bond Strength


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TJB

Advantages of SEA

Reduced chair time Etch, rinse and drying steps are

eliminated

a whole 80 seconds can be saved!

Collapse of the collagen network is

prevented This is possible in the E&R techniques if

care not exercised.


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TJB

Concerns about SEA


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TJB

Concerns about SEA


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Concerns about SEA

Phase Separation

Adhesive dispensed droplets appear rise

to surface anddisappear

Explanation Complex mix of

hydrophylic and phobiccomponents dissolvedin an organic solventwhose evaporation setsoff this event.

TJB


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Phase Separation

TJB


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TJB

Concerns about SEA


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TJB

In the bottledegradation


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TJB

Loss of Dentinal Bond


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TJB

SEA or E&R ?


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Zr Dentin and Enamel Bonding