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yr 3 - csb > FIXED PROS - Materials used for Cementation > Flashcards

FIXED PROS - Materials used for Cementation Flashcards

1
Q

describe what a cement is

A

a material which sets into a paste through a setting reaction

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2
Q

what is the purpose of dental luting cements? (4)

A
  • to provide a link between fixed prothesis and supporting prepared tooth structure
  • provides a seal
  • acts as a barrier to bacterial microleakage
  • holds tooth and restoration together through mechanical, chemical or mechanochemical.
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3
Q

what is getting cemented to what?

A

dentine is getting cemented to either: metal, porcelain or composite

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4
Q

describe the steps of cementing.

A
  1. isolate and dry prep
  2. clean and dry restoration
  3. mix cements
  4. place layer of cement in restoration
  5. seat firmly, apply pressure so excess can flow out
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5
Q

give an example of a temporary luting cement.

A

zinc oxide/eugenol

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6
Q

give 5 examples of permanent luting cements.

A
  • zinc phosphate
  • zinc polycarboxylate
  • gic
  • composite resin
  • rmgic
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7
Q

describe zinc phosphate - how it sets, what form it is in and its thickness.

A
  • sets by acid-base reaction

form:
- powder - 90% zinc oxide, 10% magnesium oxide
- liquid - 67% phosphoric acid + Al+ Zn
- water present to control ionisation of acid and rare of setting

film thickness = less than 25 micrometer

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8
Q

describe zinc phosphate - strengths, compressive, tensile, modulus of elasticity

A

strength - more powder:liquid = stronger

  • very strong, very stiff

compressive - 80-110MPa
tensile - 5-7MPa
modulus of elasticity - 13GPa

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9
Q

does zinc phosphate chemically or mechanically bond?

A

mechanically

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10
Q

when would zinc phosphate be used?

A
  • long term
  • posts
  • metal inlays, onlays
  • metal and all-ceramic crowns
  • fixed bridges
  • amalgam, composite or GIC cores
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11
Q

describe GIC - how it sets, what it consists of and its compressive strength.

A
  • acid-base reaction
  • aluminium fluorosilicate glass
  • liquid copolymers of weak polyalkenoic acids

strength = 90-230MPa

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12
Q

do GIC chemically or mechanically bond to the teeth?

A

chemically :)

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13
Q

describe RMGIC - how does it set, what is the end result of setting.

A

acid-base reaction
- powder: fluoroaluminosilicate glass
- liquid: polyalkenoic acids with mod pendant methacrylate

result
- metal polyacrylate salt + polymer

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14
Q

what is the setting of RMGIC called?

A

photochemical initiation of free radical polymerisation

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15
Q

with RMGIC, compare the compressive strength and tensile strength to other cement types.

A

higher compressive and tensile stregth than Zn phosphate, polycarboxylate and GIC

  • lower than composite
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16
Q

describe film thickness of RMGIC

A

= low

17
Q

compare RMGIC to GIC

A
  • RMGIC = less soluble - more resistant to water attack
  • higher compressive and tensile strength
  • both adhesive to enamel and dentine
  • both release fluoride
18
Q

how is RMGIC able to be non-soluble?

A

the addition of HEMA
- hydrophilic property
- has potential for dimensional change

19
Q

why is RMGIC a worry in terms of biocompatibility?

A
  • has free monomers present
  • toxicity
  • HEMA is also a known allergen to irritate the eyes
20
Q

give an example of a RGMIC. why is it different to other RGMIC’s?

A

RelyX - prev known as Vitremer
- can set without light activation = a dark cure
- self-adhesive - no need for etch, prime or bond

21
Q

what do resin composite cements consist of?

A

BISGMA resin + methacrylate

50-70% glass/silica

22
Q

how do resin composite cements cure?

A

photochemical polymerisation = dual cure

23
Q

5 advantages to resin composite cements

A
  • various shades and opacities
  • micromechanical adhesion
  • high compressive strength
  • resistant to tensile fatigue
  • insoluble in oral
24
Q

1 major disadvantage to resin composite cements

A

polymerisation shrinkage

25
Q

what are the uses of resin composites?

A

aesthetics
ceramic restorations
porcelain restorations
metal alloys
fibre reinforced composites

26
Q

give 2 examples of what may be components of resin composite materials that are able to bond well with metals.

A

superbond
contains 4-META - react with metal surface to give good bonds

MDP - panavia active monomer

27
Q

give 3 advantages to MDP and 3 disadvantages

A

advantages
- bond well to sandblasted non-precious and tin-plated surface
- good physical properties
- bonding = water resistant

disadvantages
- weak bond to dentine
- technique sensitive
- air inhibited

28
Q

why may the use of resin composite be contra-indicated if a temporary cement containing eugenol is used prior?

A

eugenol can inhibit the polymerisation of composite = compromised bond strength and setting

= they are not compatible materials

29
Q

what is the effect of resin composite having a high filler content?

A
  • increased viscosity
  • reduce flow
    = increase film thickness
30
Q

what must be the 4 properties of an ideal luting cement?

A
  • biological
  • mechanical
  • aesthetic
  • working
31
Q

describe what is meant by ideal biological properties

A
  • biocompatible
  • no interaction with oral tissues/fluids
  • non-toxic
  • low allergic potential
  • inhibits caries
  • prevents microleakage
32
Q

what 2 things are to be considered regarding aesthetic?

A
  • will the colour stay stable
  • is it radio-opaque
33
Q

what is considered regarding the working properties of the cement?

A
  • does it have low film thickness
  • does it have viscosity
34
Q

why is low film thickness important for cement? what is the ideal thickness?

A
  • lower = more retention
  • gives close relationship between restoration and tooth surface
  • ideal thickness = 25micrometer
35
Q

why is low viscosity important?

A
  • low viscosity
    = small particles
  • more flow of cement
  • reduce aggregation of particles
36
Q

how can micro fractures lead to failure?m

A

microfracture
- microleakge
- bacterial ingress
- bacterial disease

or micro fracture can lead to catastrophic failure
- entire restoration has come off the tooth

37
Q

Composite has the most ideal..

A

working time
solubility

38
Q

RGMIC has the most ideal..

A

setting time
solubility
least microleakage

39
Q

Zinc Phosphate has the most ideal…

A

thickness
elastic modulus
least pulp irritation
ease to remove excess
retention

yr 3 - csb (38 decks)

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