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My Dental Materials > Dental Cements > Flashcards

Dental Cements Flashcards

1
Q

What are dental cements?

A

Dental cements are the materials that set intraorally and are commonly used to join a tooth and a prosthesis or restoration of carious tooth.

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2
Q

Six uses of dental cement

A
  1. Cementing/luting of prosthesis and orthodontics appliance
  2. Restoration
  3. Pulp therapy
  4. Obtundant
  5. Liners and bases
  6. Root canal sealers
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3
Q

Classification of dental Cement based on application

A
  1. Type I : lutting agent
    Type I : fine grain for cementating and luting
    Type II : medium grain for bases , orthodontics purposes
  2. Type II: restorative application
  3. Type III : liners or base application
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4
Q

3 Uses of zinc phosphate cement

A
  1. Permanent cement for indirect restoration including inlays, onlays, crowns and bridges
  2. Orthodontics cement
  3. High-strength base
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5
Q

Composition of powder of zinc phosphate cement.

A
  1. Zinc oxide->75%-main constituents
  2. Magnesium oxide - 13% - aids in sintering
  3. Barium oxide - 0.2 % -radioopacity
  4. Other oxides - 1.4% - smoothness of mix and filler
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6
Q

Composition of liquid of zinc phosphate cement

A
  1. Phosphoric acid - 38%-59% - reacts with zinc oxide
  2. Water - 30%-55% - controls rate of reactions
  3. Aluminium phosphate - 2%-3% - buffer
  4. Zinc phosphate - upto 10%
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7
Q

Setting reaction of zinc phosphate

A

When mixed, phosphoric acid dissolved the zinc oxide which then reacted with aluminium phosphate to form zinc aluminophosphate gel on the remaining undissolved zinc oxide particles

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8
Q

Mixing time of zinc phosphate cement

A

1.5-2 min

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9
Q

Setting time of zinc phosphate cement

A

2.5- 8 min

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10
Q

Type of reaction zinc phosphate cement

A

Exothermic reaction

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11
Q

Control of setting time of zinc phosphate

A
  1. Manufacturing process
    * sintering temp- directly
    * particle size - indirectly
    * water content-indirectly
    * buffering agent- directly
  2. Operator control
    * temp-inversely
    * p/l ratio-directly
    * rate of addition of powder to liq- directly
    * mixing time- directly
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12
Q

Compressive stress of zinc phosphate

A

104 MPa

  • 70% strength in 30 min
  • more powder greater strength
  • water content : both loss or gain reduces the strength
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13
Q

Tensile stress of zinc phosphate

A

5.5MPa, brittle

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14
Q

modulus of elasticity of zinc phosphate

A

13GPa, stiff and resistant to elastic deformation

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15
Q

Solubility of zinc phosphate

A
  1. 06%-low
    - thick mix. : less solubility
    - water content : any change increase the solubility
    - moisture : increase
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16
Q

Thermal insulator of zinc phosphate

17
Q

pH of zinc phosphate

A

At time of cementing :2

After 24 hrs : 5.5

18
Q

Liners and bases

19
Q

2 Advantage of zinc phosphate

A
  1. Proven reliability

2. Good compressive strength

20
Q

4 Disadvantage of zinc phosphate

A
  1. No chemical adhesion
  2. No anti cariogenic properties
  3. Pulp irritation
  4. Poor esthetician’s
21
Q

First tooth coloured filling material? When?

A

Silicate cement-1870 by Fletcher

22
Q

Silicate cement is based on?

A

Fluoroaluminosilicate glass and aq. Phosphoric acid

23
Q

Silicate cement is also known as?

A

Silicophosphate cement

24
Q

Drawbacks of silicate cement?

A
  • acidic ( phosphoric acid)
  • soluble in mouth
  • low wear resistance
  • staining at the margins
  • short lasting fillings
25
Q

What is the basis of modern glass ionomer cement?

A

Fluoroaluminosilicate glass of silicate cement

26
Q

Composition of powder of silicate cement

A
  • silicon dioxide
  • sodium fluoride
  • calcium fluoride
  • aluminium fluoride
  • aluminium trioxide
27
Q

Composition of liquid of silicate cement?

A

35-50% phosphoric acid

Sodium and aluminium phosphate

28
Q

Setting reaction of silicate cement?

A
  • acid base reaction
  • powder particles are attacked by acid releasing calcium , aluminium, and fluoride ions.
  • these ions precipitates as phosphates which form continuous cement matrix along with and form a silica gel.
  • fluoride ions do not take part in this reaction. Present as free ions
  • most of the powder particles are not dissolves. Only the surfaces are dissolves.
  • finally the set cement contains a phosphate matrix containing unreacted powder particles surrounded by acid gel and fluoride ions.
29
Q

Properties of silicate cement?

A
  • anticariogenic: large amount of fluoride
  • soluble in saliva : high in acidic condition
  • coefficient of thermal expansion : close to the tooth structure : microleakage is minimal
  • good optical properties
  • pH remain low as 3 for few days: pulpal irritation
  • pH remain below 7 even after a month : severe pulpal irritant
  • adhesion : mechanical bonding to tooth structure
30
Q

Advantage of silicate?

A
  • translucency

- anticariogenic

31
Q

Disadvantages of silicate cement?

A

High pulpal irritant

-highly soluble

My Dental Materials (6 decks)

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