DMS-luting agents Flashcards
What are luting agents?
These are:
Dental Cements
Composite resins
Self-adhesive composite resins
Surface modifying chemicals.
What are the ideal properties of a luting agent?
low viscosity- to allow seating of a restoration without interference Adhesive-so that it sticks.
Easy to use (easy to mix, long working time, short setting time)
Radiopaque- so that you can see the margins in order to see secondary caries or marginal breakdown.
Bonding- we want chemical bonding to the tooth and the indirect restoration.
Cariostatic- we want it to be antibacterial around the margins of the restoration.
Biocompatible- We don’t want it to damage the pulp (by pH or heat reaction)
Mechanical properties similar to tooth tissue.
Compare zinc phosphate and zinc polycarboxylate cement.
Zinc phosphate has an exothermic setting reaction and is not adhesive.
Zinc polycarboxylate bonds to the tooth surfae and has a cooler setting reaction. But this is more difficult to use and not as strong.
What is the difference between a glass ionomer luting cement and a glass ionomer filling material?
The particle size, a glass ionomer luting cement consists of smaller particles to prevent interference with the filling material.
Compare glass ionomer cement to resin modified GI cement.
GIC- it bonds to the tooth surface chemically and to the restoration surface mechanically.
RMGIC- HEMA which can cause pulpal damage if not fully cured,
HEMA also expands in wet environments (so cannot be used to cement porcelain crowns as they will crack)
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Discuss temporary cements?
These are used to temporarily hold the restoration in place.
They are soft for easy removal
They do not stick, as a result they need a retentive preparation.
What is a temporary cement made of?
2 pastes:
Base- Contains ZnO, starch and mineral oil
Accelerator- contains resins, carnauba wax, eugenol or ortho EBA.
When would we use non-eugenol cements?
If the permanent restoration is going to be cemented with a resin cement as leftover eugenol would stop the future cement setting.
What is the function of the carnauba wax?
Weakens the cement structure to make it easy to remove .
What are composite luting agents?
Composite filling materials that have been altered to have suitable particle size and viscosity.
How do we bond a composite luting to indirect composite?
Bond chemically- due to C=C bonds on the fitting surface of the inlay.
Bond micromechanical- to the rough internal fitting surface of the inlay.
A double cure is needed because the light cannot penetrate the inlay.
How do we bond a composite luting agent to porcelain?
We need to:
Etch the surface
Surface wetting to make the luting agent hydrophillic (allowing bonding)
This requires a longer curing time as some of the light is dissipated by the porcelain.
How do we bond a composite luting agent to a non-precious metal
Use electrolyte etching (which removes different phases of the alloy at different rates)
It must be duel cured as light will not penetrate the metal.
Compare self-adhesive and self-etching composite resin .
Self-adhesive resin is a metal coupling agent incorporated into the composite resin.
A self-etching resin is a combination of a composite resin cement and a self-etching dentine bonding agent.
How does a self-etching composite resin bond to enamel?
Not well, so enamel should be etched before bonding.
