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BDS3 DMS > Dental luting agents > Flashcards

Dental luting agents Flashcards

(63 cards)

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1
Q

What is luting agent another word for?

A
  • Dental cement
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2
Q

What is the ideal film thickness of luting agent?

A
  • 25um or less
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3
Q

What is the ideal viscosity for luting agent?

A
  • Must be low to allow seating of restoration without interference
  • Viscosity increases as material sets therefore must seat restoration quickly and maintain pressure
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4
Q

What ease of use properties should luting agents have?

A
  • Easy to mix i.e via clicker system in encapsulated ones
  • Working time long to allow for seating of restoration
  • Setting time short
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5
Q

Why must luting agents be radiopaque?

A
  • Some ceramic crowns are radiolucent
  • Makes it easier to see marginal breakdown
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6
Q

Ideally how should a luting agent bond to tooth and indirect restoration?

A
  • Bond chemically to tooth and indirect rest with a permanent and impenetrable bond
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7
Q

What is the ideal aesthetics of luting agents?

A
  • Tooth coloured with variation in shades and translucency
  • Non staining
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8
Q

What is the ideal solubility of luting agent?

A
  • Low
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9
Q

What is the ideal cariostatic properties of luting agents?

A
  • Fluoride releasing
  • Antibacterial
  • Important in preventing secondary caries around crown margins
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10
Q

What is the ideal biocompatibility of luting agents?

A
  • Non toxic
  • Not damaging to the pulp (inappropriate pH and heat on setting)
  • Low thermal conductivity
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11
Q

What are the ideal mechanical properties of luting agents?

A
  • High compressive strength (dentine 275MPa)
  • High tensile strength (dentine 50MPa)
  • High hardness value (dentine 70K and enamel 400k)
  • Young modulus similar to tooth (dentine 15GPa)
  • No luting agent gets close to tooth values for more than one or two physical properties*
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12
Q

What are the types of dental cement?

A
  • Zinc phosphate
  • Zinc polycarboxylate
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13
Q

What are the types of glass ionomer cement?

A
  • Conventional
  • Resin modified
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14
Q

What are the types of composite resin luting agents?

A
  • Total etch for use with DBA
  • Self etch
  • Requires etch but has own bonding agent incorporated
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15
Q

What is zinc phosphate?

A
  • In use for 100+years
  • Acid base reaction
  • Powder and liquid
  • Excellent clinical service
  • Easy to use
  • Cheap
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16
Q

What is the constituents of zinc phosphate powder?

A
  • Zinc oxide >90% (main reactive ingredient)
  • Magnesium dioxide <10%
  • Other oxides (alumina and silica)
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17
Q

What is magnesium dioxide used for in zinc phosphate powder?

A
  • Gives white colour
  • Increases compressive strength
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18
Q

What are alumina and silica used for in the powder of zinc phosphate cement?

A
  • Improves physical properties
  • Alter shade of set material
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19
Q

What are the constituents of zinc phosphate liquid?

A
  • Aqueous sol of phosphoric acid (approx 50%)
  • Aluminium oxide that ensures even consistency of set material
  • Zinc oxide slows the reaction giving better working time
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20
Q

What are the reactions of the zinc phosphate cement?

A
  • Initial acid base reaction
  • Followed by hydration reaction
  • Results in formation of crystallised phosphate matrix
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21
Q

What does the aluminium oxide prevent in Zinc phosphate?

A
  • Prevent crystallisation leading to amorphous glassy matrix of acid salt surrounding unreacted ZnO powder
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22
Q

What happens when zinc phosphate cement matures?

A
  • Matrix originally insoluble but it is porous and contains free water from setting reaction
  • When it matures it binds the water
  • Leads to stronger, less porous material
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23
Q

What are the disadvantages of zinc phosphate cement?

A
  • Low initial pH approx 2
  • Exothermic setting reaction (release heat)
  • Not adhesive to tooth or restoration
  • Not cariostatic
  • Final set takes 24hrs
  • Brittle
  • Opaque
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24
Q

What can a low pH lead to?

A
  • Pulpal irritation
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25
How is zinc phosphate retained in tooth?
- Works like grout on tiles and fills spaces - Retention slightly micromechanical due to surface irregularities on prep and restoration
26
What are the constituents of Zinc Polycarboxylate cement?
- Aqueous sol of polyacrylic acid (approx 50%) - Aluminium oxide - Zinc oxide - Zinc oxide >90% (main reactive ingredient) - Magnesium dioxide <10% - Other oxides (alumina and silica)
27
What are some negatives of Zinc Polycarboxylate cement?
- Difficult to mix - Difficult to manipulate - Soluble in oral environment at lower pH - Opaque - Lower modulus and compressive strength than Zinc phosphate
28
How does the glass ionomer cement bond to tooth surface?
- Ion exchange with calcium in enamel and dentine - Hydrogen bonding with collagen in dentine - Results in fairly strong, durable bond to tooth - No chemical bond to restoration surface
29
What are the advantages of glass ionomer cements?
- Clinically easy to use and durable cement - Low shrinkage - Long term stability - Relatively insoluble once fully set - Aesthetically better than Zinc phosphate - Self adhesive to tooth substance - Fluoride release - Cheap
30
What monomer does the RMGI cement liquid have in addition to conventional GIC powder?
- Hydrophillic monomer - Must be hydrophilic as GIC is water based material - HEMA (Hydroxyethyl methacrylate)
31
How is the RMGI set?
- Light activation causes polymerisation of HEMA and any copolymers = rapid initial set - Acid base reaction continues for some time - Some materials have secondary cure via REDOX - Allows Dark curing
32
What is Dark curing?
- Material not exposed to light will cure
33
What are some advantages of RMGI?
- Shorter setting time - Longer working time - Higher compressive and tensile strengths - Higher bond strength to tooth - Decreased solubility
34
What are some potential problems with RMGI?
- HEMA is cytotoxic (can damage pulp if any remain) - HEMA swells (expands in wet environment so can't use conventional porcelain crowns as may crack - No bond to indirect restoration
35
What are the advantages and disadvantages of composite luting agents?
- Can be light or dual cured - Better physical properties, lower solubility and better aesthetics - But technique sensitive
36
What are the advantages and disadvantages to bonding to indirect composite?
- Composite bonds to composite - Bond strength lower to inlay fitting than new composite - Bond is micromechanical to rough internal surface of inlay - Bond is chemical C=C bonds on fitting surface of inlay - Use dual curing cement as light penetration through inlay is poor
37
Why does porcelain need to be treated with 10% HF in order to bond to tooth?
- Porcelain is brittle and needs to be bonded to tooth to prevent fracture - Untreated porcelain is smooth and non retentive - Treated with HF to etch surface (toxic) - Leads to rough retentive surface - Allows silane bonded coupling agent to adhere
38
What is a silane coupling agent and how does it bond?
- Gamma-methacryoxypropyltrimothoxysilane - Applied to etched porcelain surface as monolayer - Strong bond between oxide groups on porcelain surface and silane - Other end of silane molecule has C=C bond which reacts with composite resin luting agent - Works same manner as dentine bonding agent
39
When curing a composite luting agent to porcelain what should you do?
- If porcelain restoration is thin use light cured - If thick use dual cure - Remove as much of the luting resin as poss before curing
40
How does composite materials bond to metal?
- Does not bond directly to metal - Metal surface to be roughened by etching - Usually done by sandblasting
41
What does etching metal lead to?
- Electrolytic etching removes diff phases of alloy at different rates - Gives very retentive surface - But technique sensitive - Beryllium alloy works best - Can't etch precious metals at all
42
What is required after sandblasting a metal?
- Sandblasting roughen surface - Does not give undercut surface of etching - Chemical bonding required to strengthen bond
43
How are non-precious metals bonded?
- MDP and 4-META - Molecules have acidic end and C=C end - Acidic end of molecule reacts with metal oxide and surface is now hydrophobic - Use dual cure as light doesn't penetrate metal
44
How are precious metals bonded?
- Change precious alloy composition to allow oxide formation - Increase copper content and heat 400oC in air - Tin plate - Sulphur based chemistry of bonding agent - Complicated and technique sensitive
45
What are the advantages of self adhesive composites resins?
- Good film thickness - Opaque - Moisture sensitive - Expensive
46
What is a self adhesive composite resin?
- Metal coupling agent incorporated into composite resin - Simplifies bonding process
47
What are the advantages and disadvantages of Self etching composite resin cements (Rely X Unicem)?
- Stick to everything - Easy to use - Requires good moisture control - Potential inadequate bond strength to enamel due to inadequate etching - pH of carboxylic monomer doesn't stay low enough enough for good etch
48
How do Self etching composite resin luting agents work?
- Acidic group binds with calcium in hydroxyapatite - Forms stabilising attachment between tooth and resin - Ions from dissolution of filler neutralise remaining acidic groups - Forms chelate reinforced methacrylate network - Limited removal of smear layer or sig infiltration into tooth surface - Good bond strength to dentine
49
What are the properties of Self etching composite resin luting agents?
Mechanical - Compressive strength - Tensile strength - Hardness - Wear resistance *Slightly lower than conventional resin luting agent's but better than cements
50
When using a MCC what luting agent should you use?
- Glass ionomer cement - RMGI
51
When using metal post what luting agent should you use?
- GIC
52
When using a fibre post what luting agent should you use?
- Dual cure composite and DBA - Self adhesive composite
53
When using veneer what luting agent should you use?
- Light cure composite and DBA
54
When using adhesive bridge what luting agent should you use?
- Anaerobic cure composite
55
When using zirconia crown what luting agent should you use?
- GIC - RMGIC - Dual cure composite and DBA - Anaerobic cure composite - Self adhesive composite
56
When using composite inlay what luting agent should you use?
- Dual cure composite and DBA - Self adhesive composite
57
When using porcelain inlay what luting agent should you use?
- Dual cure composite and DBA - Self adhesive composite
58
When using gold restoration what luting agent should you use?
- GIC - RMGIC
59
What are temporary cements used for?
- Cement temporary restorations in place whilst permanent restoration is fabricated - Soft for easy removal and some don't even set - Prep must be physically retentive or doesn't work
60
What are temporary cements made of?
- Two paste system (base and catalyst/accelerator) - Base = ZnO, Starch and mineral oil - Accelerator = resins, eugenol or ortho-EBA and carnauba wax
61
What is the wax for in temporary cements?
- Weakens structure of set cement - Makes it easier to remove - Can be made even weaker with petroleum jelly
62
What are the two types of temporary cements?
- With and without eugenol
63
What can't eugenol containing temporary cements be used for?
- Not used to cement provisional restoration where permanent restoration will be cemented with resin cement - Any eugenol residue can interfere with setting of resin cement

BDS3 DMS (10 decks)

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