Setting Calcium Hydroxide Cement Flashcards Preview

Semester II - Dental Materials > Setting Calcium Hydroxide Cement > Flashcards

Flashcards in Setting Calcium Hydroxide Cement Deck (18)
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1

What's the old classification of a Base and Lining?

Base:
- Barrier against chemical irritation
- Provide thermal insulation and resist forces applied during condensation of the restorative material
- Malleable
"Dentine replacement material"

e.g.
1. Zinc oxide eugenol
2. Zinc phosphate
3. Glass ionomer cements

Lining:
- Placed as thin coating on the pulpal surface
- Barrier against chemical irriation
- DO NOT FUNCTION as thermal insulators

e.g.
1. Varnish-type materials which calcium hydroxide OR zinc oxide powder are added

2

What's Calcium Hydroxide cement?

- Lining material

- Reaction between Calcium hydroxide & Salicylate esters forming a calcium disalicylate complex

- 2 paste system

- Available as light-curing product - BUT calcium hydroxide is not available or any reaction with tooth (bound in resin)

3

What's the setting reaction of Calcium Hydroxide cement?

- Chelation reaction between calcium and butylene glycol disalicylate

(Water is required)

- Exothermic reaction but of negligible significance

-End result = calcium disalicylate complexes surrounding unchanged calcium hydroxide

4

What are the mechanical properties of Calcium Hydroxide cement?

- Poor mechanical strength (weakest of all cements)

- Deforms in shape once you load it with another material on top

- Must be used in thin section (air thinned)

5

What's the solubility of Calcium hydroxide cement?

- Unstable and soluble
- Degrades in the presence of water
- Hydrophilic sulphonamide plasticiser included to control viscosity but permits rapid water permeation

- The high solubility facilitates the breakdown of the cement = degradation - that's why you need to place something on top to minimise moisture

- Cements degrade over & lost lowly due to marginal leakage and presence of moisture from dentine

6

How biocompatible is Calcium hydroxide?

Chemical Irritant

- Increases the pH of the local environment making it bactericidal or bacteriostatic

- Extent of effect depends on pH of surroundings in which bacteria thrive

7

What's the mode of action or Calcium hydroxide?

- Causes series of inflammatory reactions

- High pH (alkalinity) causes liquefaction necrosis of the superficial pulp -- removes up to 1.5mm of the inflamed tissue

- Neutralisation of toxicity follows in the deep layers with coagulative necrosis -- irritates adjacent pulp and causes minor inflammation

= Dentine bridge formed

1. Pleuripotential pulpal cells stimulated and differentiate into odontoblasts

2. Reparative (tertiary) dentine laid down forming a calcified bridge so walling off pulp from base of cavity

- Calcium for new dentine derived from pulp cells not cement

8

Does Calcium Hydroxide bind to the dentine?

No - no adherence either chemically or micromechanically

9

How does light-cured calcium hydroxide cements differ to regular cement?

- Addition of resin -- bis-GMA and HEMA

- Calcium hydroxide plays no part no part in setting reaction -- no dissolution of calcium hydroxide

- HEMA allows water ingress

10

What are the characteristics of Light cured calcium hydroxide cements?

- Higher exothermic reaction during polymerisation process = potential risk when placed close to pulp

- Slightly higher mechanical strength + less brittle

- Can allow microleakage -- periphery of cement lifts during polymerisation shrinkage

BUT

- Seals dentinal tubules

11

What are the advantages of using calcium hydroxide cements?

1. Stimulates the formation of reparative dentine

2. Forms a physical barrier over exposed pulp + seals dentinal tubules

3. Cheap

12

What are the disadvantages of using calcium hydroxide cements?

1. Low compressive strength

2. Soluble = breaks down during use

3. No adhesion to dentine

4. High pH on setting causes local irritation

5. Chance of microleakage if using light-cured material due to polymerisation

13

What are the indications for using Calcium hydroxide?

1. Deep cavity over pulpal floor
2. Indirect pulp capping
3. Direct pulp capping

14

What is pulp capping?

- A method by which a physical barrier between the (exposed) pulpal tissue and the other material(s) used to restore the cavity

- Many restorative materials are contraindicated to be directly placed on exposed dentine as they are cytotoxic

15

What is the preferred alternative to Calcium Hydroxide?

Tricalcium Silicate Cement

- Used for indirect or direct pulp caps - forms seal and excellent biocompatability

16

How do you place Calcium Hydroxide?

- Must be placed in small thin layer on base of cavity and then air thin

- Cover with glass ionomer cement

- Sets in 2-3 minutes

17

What Calcium Hydroxide product is used in the Dental school?

Life by Kerr Hawe

18

Summarise Calcium Hhydroxide?

- Used as lining material on pulpal surface

- Stimulates tertiary dentine formation to protect the pulp

- Cover with another material to seal and prevent degradation