Plastic Restorations - Compomers Flashcards Preview

Semester II - Dental Materials > Plastic Restorations - Compomers > Flashcards

Flashcards in Plastic Restorations - Compomers Deck (19)
Loading flashcards...
1
Q

What are Compomers?

A

Developed to combine advantages of fluoride release with resin composites - RESIN COMP WHICH EXHIBITED A SUSTAINED AND EFFECTIVE RELEASE OF FLUORIDE

  • Primarily a resin system with an additional (difunctional) resin is incorporated
2
Q

What’s the generic name of Compomer?

A

Polyacid-modified resin composite

  • Describes their composition and by implication their setting mechanism
3
Q

What are the Resin constituents of Compomer?

A

Contains 2 monomeric components:

  1. Dimethacrylate (urethane dimethacrylate)
  2. Difunctional resin monomer containing both carboxyl and methacrylate groups
4
Q

What’s Difunctional Resin Monomer

A

TCB resin = reaction product of butane tetracarboxylic acid and hydroxyethylmethacrylate

  • cross-linking agent in a primary reaction
  • Source of carboxyl groups for 2nd reaction with glass

Hydrophilic monomers - enhances water diffusion within resin matrix

  • Hydrophobic and Hydrophilic ends
5
Q

What are the other constituents of Compomer?

A

Filler:

  • Fluoro-alumino-silicate glass (glass ionomer cement)
  • Imparts strength
  • Source of fluoride ions for use in 2nd reaction
  • Forms a salt matrix with carboxylate groups
  • Filler loading volume of between 42 & 67%
  • Contain lithium to convey radiopacity

Photo-activators & Initiators:

  • Camphorquinone
  • Tertiary amine
6
Q

What’s the setting reaction for Compomer?

A

2 stages - primarily a polymerisation reaction which is complete on exposure to curing light energy

Stage 1:

  1. Initial setting reaction is initiated by light
  2. Free radical polymerisation reaction
  3. Cross-linking of the end groups on the UDMA and Methacrylate groups to form a resin polymer matrix which the glass is trapped

(Difunctional monomer binds to dentine)

Stage 2:

  • 2nd reaction occurs between the glass and carboxylate groups of the difunctional resin
  • Requires restoration to be bathed in saliva
  • Water is taken up by the resin system
  • Hydrogen ions dissolve the outer surface of glass and release the fluoride ions
  • Polysalt matrix is formed around the glass as fluoride is release
  • Acid/base reaction that is aided by additions of small percentages of hydrophilic resin to the resin mi to encourage diffusion of water within the resin and fluoride out of it – diffusion takes several weeks
7
Q

What are the mechanical properties of Compomer?

A

Compared to resin comp, it has lower:

  1. Compressive strengths
  2. Flexural strengths
  3. Elastic moduli
  • Not useful for higher stress situations
8
Q

What are the physical properties of Compomer?

A
  • Displays polymerisation shrinkage due to resin - OCCURS IMMEDIATELY ON LIGHT CURING
  • Can disrupt any bonding that is being formed
  • Compensate for poly shrinkage should be same as resin comp
9
Q

Should an intermediate bonding system be used for Compomer?

A
  • YES
  • Needed to achieve adhesion to too tissue
  • Little or no adhesion achieved as a result of 2ndary setting reaction
  • No chelation reaction unless the carboxylate groups are in close prox to the tooth surface
10
Q

Do you etch with Compomers?

A
  • Don.t need to etch
  • Recommended though by some manufacturers as no acid etching results in reduced bond strength - so etch to maximise adhesion
11
Q

How if fluoride released?

A
  • Fluoride release is inferior to Conventional GIC
  • Dependent on secondary setting reaction which occurs after placement
  • Slow steady release with little fluoride burst seen initially
  • Fluoride release is dependent on conc gradient between external environment and the restoration surface for diffusion of the fluoride ions
  • Surface of restoration has a greater flu ion conc then the surroundings then migration of ions occurs
12
Q

What determines the concentration of fluoride viable for release in Compomer?

A
  • Rate of secondary reaction of the glass with the pendant carboxyl groups - determined by their proximity to the reactive glass surface
13
Q

What’s the influence of water sorption within Compomer?

A

Typically water sorption adversely affects most hydrophobic resin systems

  • Addition of hydrophilic resin can facilitate uptake of water and this material cannot fully set until water sorption has occurred and the secondary glass filler/carboxyl reaction has been completed
  • Saturation occurs within a week of placement in the mouth
14
Q

What is a potential drawback and benefit of water sorption?

A

Drawback:
- Uncontrolled reaction may lead to excessive expansion of the material with the risk of damage to the tooth

Benefit:
- Expansion may offset poly shrinkage

-

15
Q

What are the other drawbacks of water sorption with Compomer?

A

Uptake of fluids leads to discolouration of restoration - relatively shortly after placement

16
Q

How resistance to wear is Compomer?

A

Poor resistance - wear observed quite quickly after placement

17
Q

What are the indications for Compomer?

A

Class III cavities - strong enough and aesthetically acceptable (I woudn’t recommend though)

Class V cavities - flexible matrix so able to retain in abfraction lesion

Restoration of deciduous teeth - bonds to tooth tissue

18
Q

What are the contraindications for Compomer?

A

Where aesthetics is important - composite is better doesn’t stain like compomer

Core build-ups - not strong enough as water uptake is needed to fully cure material

Class I, II, IV cavities - material not strong enough

Inter-visit restoration of endodontic access cavities - poor ability to seal as demonstrated by microleakage studies

19
Q

Summary

A
  • Relatively limited area of application

- Sticky in nature so handling can be difficult