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