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Flashcards in 7 - Luting Cements Deck (44):

2 types of restorations? describe how each is done + give 3 examples of each

- direct restoration: material placed in/on a cavity which hardens into a solid (chemically or by light curing)
e.g. amalgam, composite, GI restorations

- indirect restorations: a solid object made outside of the mouth which is placed in/on a prepared tooth
e.g. crowns, bridge, veneer, inlays, onlay
* can be provisional/temporary or definitive


die relief - helps to do what?

die relief helps to accommodate the thickness of luting cements


what is a luting cement? what are its 2 main purposes?

it is a material used for the
1) retention of indirect restorations, and to
2) seal the space between restoration and the tooth


choice of luting cement depends on?

- choice of luting cement depends on the type of restoration being cemented
1. provisional/temporary?
2. material of indirect restoration:
- metal? ceramic? composite?
3. type of restoration?
- veneer? resin retained bridge? conventional bridge?


2 types of luting cement?

- active luting material
- passive luting material


active luting material: what does it do? and what are its roles?

- it bonds to the tooth and the restoration
- helps with retention
- provides a marginal seal


passive luting material: what does it do? how does it bring retention?

- it fills the gap between tooth and restoration
- there is no bond between tooth and restoration, instead retention is brought about by method of tooth tooth preparation


what are the methods of tooth preparation?

- taper
- preparation height
- surface roughness
- mechanical interlocking


general ideal properties of a luting cement?

- biocompatible
- retention
- mechanical properties
- marginal seal
- low film thickness
- ease of use
- pseudoplastic
- radiopacity
- aesthetics: ceramic restorations
- inhibit plaque accumulation
- antibacterial
- clear up of excess
- good shelf life


ideal luting cement: importance of biocompatibility?

able to contact with tooth tissue and periodontal tissues


ideal luting cement: importance of retention?

additional bonding for active luting cements, preparation morphology and mechanical interlocking of irregularities for passive luting cements


ideal luting cement: examples of ideal mechanical properties?

high tensile strength, fracture toughness, fatigue strength, wear resistance


ideal luting cement: importance of marginal seal?

low solubility. advantageous for active luting, reduced hypersensitivity


ideal luting cement: importance of low film thickness?

- allows full seating of restoration
- good marginal adaptation


ideal luting cement: in what ways should it be easy to use?

- powder:liquid ratios
- working and setting times


ideal luting cement: describe how it should be pseudoplastic?

it should coat the fit surface of the restoration without slumping, but it should also flow readily under pressure on fitting


ideal luting cement: how can it inhibit plaque accumulation

it should be easy to polish
it should eliminate the air inhibition layer in resin composites


passive luting cements: 4 examples? what are they based on?

- zinc phosphate
- zinc polycarboxylate
- glass ionomer luting materials
- resin modified glass ionomer luting cements

- all are water based


zinc phosphate luting cements: what is its presentation?

- powder: zinc oxide, up to 10% magnesium oxide (improves compressive strength, adds colour)
- liquid: aqueous phosphoric acid (45-64%)


zinc phosphate:
working time?
how to extend setting time?
what does using a chilled glass slab help with?

- 3-6 minutes
- by slaking the fluid; small amount of powder added to fluid about 1 minute before
- increases working time
increases powder incorporated
increase strength
decreases solubility


zinc phosphate: setting reaction
- what kind of reaction?
- describe the reaction that occurs
- how does viscosity change?
- how much strength in 10 mins? how long does it take to reach full strength?
- how does the size change on setting?
- antibacterial effect?

- acid base reaction
- dissolution of surface of ZnO powder. insoluble hydrated zinc phosphate matrix crystals effective bind to the unreacted ZnO particles
- viscosity increases rapidly
- 50% strength in 10mins, 100% str in 24 hours
- shrinks slightly on setting
- no antibacterial effect


zinc phosphate
- initially unset material has what pH
- pH depends on?
- what is this relevant to?
- describe properties

- 1.6-3.6
- depends on thickness of mix
- relevant to vital pulp
- good compressive strength,
low tensile strength (brittle)
high solubility


zinc polycarboxylate
- presentation?
- alternative presentation?

- 1. powder: zinc oxide + up to 10% magnesium oxide
2. aqueous copolymer of polyacrylic acid (30-40%), high viscosity

- acid freeze dried and added to powder
- liquid: distilled water


zinc polycarboxylate - setting reaction
- acid dissolves what?
- zinc ions form cross links between what?
- unreacted powder bound where?

- zinc oxide
- zinc ions form cross links with carboxyl groups on polyacrylic acid polymer chains
- unreacted powder bound in matrix of zinc polyacrylate


zinc polycarboxylate:
working time?
- how can it be extended?
what causes it to have a short working time? what can altering the ratio have an impact on?
appears viscous but is actually _____?

- 30-40s
- extended by adding tartaric acid and mixing on a cold glass slab
- high powder:liquid ratio. altering the ratio would have an impact on the physical properties
- appears viscous but is actually pseudoplastic


zinc polycarboxylate:
initial pH? how does this relate to pulp?
how does the pH change?
antibacterial effect?
adhesive to?

- initial low pH (3-4)
- less injurious to pulp
- pH increases rapidly
- it has antibacterial properties
- adhesive to enamel, dentine, and some metals (via oxide layer)


zinc polycarboxylate:
- describe its compressive str and tensile strength
- how much strength is reached in 1 hour?
- soluble in?
- clean up?

- low compressive strength, high tensile strength
- 80% str
- soluble in acid
- messy to clean up


glass ionomer:
how is it different from the restorative glass ionomer?
alternative presentation?

- same chemistry, but luting GI has smaller glass particle size
- presentation:
1. powder: fluoro-alumino-silicate glass
2. liquid: aqueous poly alkenoic acid

- alternatively:
1. acid freeze-dried, added to powder
2. liquid: distilled water


glass ionomer
setting reaction?
+ what element is responsible for strong cross linking?

- chemical set
1. dissolution: calcium ions released first, then aluminium
2. gelation
3. hardening: aluminium trivalent, slower to be released from glass, ensures strong cross linking of polymer chains


glass ionomer:
setting reaction -
- dissolution and initial set: how long?
- seated by how long?
- hardening can take up to how long?
- need protection to prevent what?

- 3-6minutes
- 2-2.5mins
- up to 7 days
- need to prevent dissolution or contamination


glass ionomer - properties?
what may cause pulpal inflammation?
how does it compare to zinc oxide cements?

- anti-caries effect via fluoride release
- initial acidity may cause pulpal inflammation
- 1. better compressive str
2. low tensile str and fracture toughness
3. less soluble


resin modified glass ionomer:

1. components of GI + monomer (HEMA, Bis-GMA)

*no photo initiator, chemical cure only (acid base reaction of GI)


resin modified glass ionomer: advantages over GI?

- low solubility
- improved biocompatability
- improved fluoride release
- improved physical properties
- improved adhesion to tooth tissue


RMGI cements - disadvantages?

- can undergo hygroscopic expansion
- avoid under conventional all-ceramic crowns
- suitable under zirconia core / CAD-CAM crowns


resin based luting cements: what are the constituents that are in restorative composite resins as well?
why does it have lower viscosity?
how are most of them cured?

- silenated filler
- resin e.g. bis GMA

- low filler content -> low viscosity

- mostly dual cured (chemical and light)


resin based luting cements:
conventional resin luting cements - for use with?

- all ceramic restorations
- indirect composite or quartz fibre posts e.g. veneers, dentine bonded crowns


chemically adhesive resin luting cements: for?

- for adhesively bonding to metals
(resin retained bridges, metal veneers, poorly retained indirect restorations)


resin luting cements: bonding to ceramic
- how does it bond to tooth?
- when bond has to fit surface of cermic: etched with? what is applied before cementing? what kind of bond is each one?

- conventional way: acid etch, rinse, dry, DBA

- etched with hydrofluoric acid - micromechanical bond
- silane coupling agent applied and air dried - chemical bond


hydrofluoric acid:
why lab use only?
why must it be neutralized?
why will it not etch periphery of veneers well?
- can cause damage to?

- because it is very toxic
- to prevent it from leaching out and causing tissue damage
- because it tends to slump
- to periphery of ceramic


veneers: how does try in paste change its appearance?

- it causes more light to be transmitted, less light reflected


veneers: what is applied on top of enamel to be treated?

1. etch and DBA
2. resin luting cement
- hydrofluoric acid etch fit surface + silane coupling agent


bonding to metal
- how to bring micromechanical retention?

- roughen the fit surface with 50micrometer alumina grit


bonding to metal -
chemically adhesive resin luting cement:
what kind of chemical?
name 2 monomers
both have high affinity for?

- modified bis-GMA resin

1. carboxylic monomer (4 META), e.g. C&B Superbond
2. phosphate monomer (MDP), e.g. Panavia 21, F

- both have high affinity for metal oxide on base metal alloy


bonding to metal - precious alloys:
- chemically adhesive resin luting cement?
- how to modify fit surface?

- low affinity

- tin plate: irregular surface, attracted to tin oxide on alloy surface
- silica coating to metal: then use silane coupling agent
- metal primers: bifunctional monomers - one end methacryl group, other mercapto or thiol group