Cements Flashcards
What are the uses of dental cements?
- Cavity lining material
- Luting cements
- Temporary restorations
- Endodontics
Name some requirements for cavity lining materials
- Protect the pulp from thermal, chemical or electrical stimuli
- Ability to flow into cavity
- Withstand pressure of restorative material on top
- Radio opaque
- Compatible
- Rapid setting time
What does the integrity of cement material depend on?
- Degree of set
- Material thickness
- Pressure exerted when placing
- Amount of surrounding tooth
- Handling
What are the two pastes for CaOH cement?
Calcium hydroxide with zinc oxide
Butylene glycol disalicylate
Are calcium hydroxide cements strong or weak?
Weak - less compressive strength
What is MTA composed of?
- Tricalcium silicate
- Dicalcium silicate
- Tricalcium aliminate
- Bismuth oxide
Why does MTA lead to the discolouration of surrounding oral tissue?
Bismuth oxide
What does biodentine have in it to increase the reaction rate?
Calcium chloride (Accelerator)
Why can biodentine lead to hydroxyapatite formation?
Source of calcium release
What are the main requirements for dental luting cements?
- Ease of manipulation
- Flowable into cavity
- Long working time with rapid set
- Low solubility in oral fluids
- Adequate tensile and compressive strength
- Adhesion to tooth tissue
- Radio - opacity
- Biocompatible
In zinc phosphate cements, what is the concentration of the phosphoric acid?
40-70%
Why do we have small amounts of zinc and aluminium within the phosphoric acid used for zinc phosphate cements?
Act as buffers
What can we do when mixing zinc oxide and phosphoric acid to alter the reaction rate?
1) Warm the pad mixing occurs on
2) Moistures accelerates the reaction
3) Rapid addition of powder accelerates the reaction
4) High powder:liquid ratio
What concentration of poly acrylic acid do we use when mixing up for zinc polycarboxylate cements?
32-40%
Why does zinc phosphate cements cause more sensitivity than zinc polycarboxylate cements?
Phosphoric acid has a much lower pH than polyacrylic acid
Why is white rosin added to zinc oxide eugenol?
To enhance the working time and the strength of the cement
Why is zinc oxide eugenol a temporary cement only?
It easily hydrolyses to 2 eugenol molecules and one zinc iron
Why is the eugenol molecule a free radical sink?
Presence of a carbon carbon double bond
What can we add to zinc oxide eugenol cements to modify them?
Why do we do this?
Added filler particles that are used in composite (silica, quartz).
Overcome high solubility and low strength of normal zinc oxide cement.
What are the two barrels in a self adhesive resin cement?
Barrel 1 = functional acidic monomers
Barrel 2 = usual composites of resin composites (bisGMA and filler particles)
Why is resin cement contraindicated with resin cement?
They contain amide co-initiators which can cause a yellowing effect of the veneer.
The sealants used in endo treatment need to be what?
- Insoluble in tissue fluids
- Ability to seal the whole canal
- Low viscosity, adequate working time and setting over hours
- Retain the seal over time
- Good biocompatibility
- Adequate strength
What two forms does GP exist in?
Cis and Trans form
Trans used in dentistry
For a trans isomer of GP, there is an alpha and beta form. What is the difference in the packing for each?
Alpha : used in heat packing as it is thermoplastic so can be softened with heat application
Beta : cold packing technique
What are the pros and cons or GP?
+ Semi plastic allows for reshaping
+ Biocompatible
+ Radioopaque
+ Can be replaced if needed
- Lack of malleability makes placement hard
- Ages rapidity and go brittle
- Needs to be used with sealers
What are the 4 main types of sealers used with GP?
Zinc - oxide eugenol
Epoxy Resin
Gutta percha dissolved
Cements - GIC, zinc polycarboxylate, zinc phosphate
