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Fixed Prosthodontics > Try-In and Cementation of Crowns > Flashcards

Try-In and Cementation of Crowns Flashcards

1
Q

What is a luting agent

A

This is a type of cement that can be used to secure dental restorations

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2
Q

What types of Luting agent are there

A
  • Non-Adhesive

- Adhesive

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3
Q

What type of preparation are non-adhesive and adhesive luting agents reliant on

A

Non adhesive = Retentive preparation

Adhesive = On micro-mechanical retention/bond, Unretentive preparations

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4
Q

What kinds of restoration are non adhesive luting agents used on

A
  • Crowns
  • Retentive Onlays
  • Cast custom made posts
  • Some prefabricated posts
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5
Q

Name some kinds of non-adhesive luting agents used as cements for pros

A
  • Zinc Phosphate
  • Zinc Polycarboxylate
  • Glass Ionomer
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6
Q

Name some kinds of adhesive luting agents used as cements for pros

A
  • Resin based cements

- Glass ionomer compomer based

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7
Q

What kinds of restoration are adhesive luting agents used on

A
  • Crowns
  • Resin bonded bridges
  • Inlay/Onlay
  • Veneers
  • Prefabricated posts: non-metal posts
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8
Q

What stages are there in the try-in procedure for crowns

A
  • Check crown on die
  • Seat crown
  • Assess seated crown
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9
Q

What are you looking for when checking the crown on the die

A
  • Casting nodules or bubbles

- Check the die for damage e.g. margin deficiencies and proximal contacts of adjacent teeth

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10
Q

Why is it preferable to not administer LA when seating the crown in the patient’s mouth

A

So that the patient’s proprioception is not impaired which is valuable in assessing occlusion and tight proximal contacts

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11
Q

Describe what is done to evaluate the complete seating of a crown

A
  • Using different sized tip explorers at the sub-gingival margins with varying angles of approach to try and dislodge the crown

Lecture doesnt specify what means that there is successful seating

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12
Q

What types of defective crown margins are there

A
  • Over-extended (beyond finish line)
  • Under-extended margin (ledge)
  • Over contoured (thick)
  • Open Margin
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13
Q

What are the potential causes of an over-extended margin in crowns

A
  • Poor impression
  • Surplus untrimmed wax or ceramic
  • Improperly trimmed die
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14
Q

What are the potential causes of an under-extended margin (ledge) in crowns

A
  • Poor impression
  • Overpolished casting
  • Improperly trimmed die
  • Difficulty identifying finish line
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15
Q

What are the potential causes of an over contoured margin in crowns

A
  • Over waxed
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16
Q

What are the potential causes of an open margin in crowns

A
  • Casting not properly seated
  • Poor impression
  • Incomplete casting
  • Improperly trimmed die
  • Over-polished casting
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17
Q

What aspected of a seated crown should be assessed to determine how good it is

A
  • Proximal contacts
  • Marginal fit
  • Aesthetics
  • Occlusion
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18
Q

How can you assess the proximal contacts of a crown

A
  • Should be as tight as other proximal contacts in the mouth
  • Hold crown firmly and test with floss
  • If both are too tight, adjust the tighter one first
  • Open contacts need to be modified in the lab
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19
Q

What amount of marginal opening is the borderline or acceptable

A

100um.

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20
Q

How can over-extended margins be corrected

A

Adjusting the crown from its axial surface (never from underneath) - soflex discs are useful for this

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21
Q

How can deficient margins or negative ledges be fixed

A

These faults need a remake of the crown or even of impression

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22
Q

What can be used to located any internal discrepancies in crowns

A
  • Using a dry aerosol indicator (occlude), disclosing wax or impression type materials e.g. light bodied silicone
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23
Q

What can be used to adjust metal-ceramic crowns

A
  • Diamond burs and the addition of ceramic
24
Q

What can be done to improve the shade of a crown

A

You can add stains

25
Q

When is the occlusion checked for a crown

A

Occlusion should always be the first and last to be checked

26
Q

How can you mark the high spots of the occlusion on a crown

A

With GHM articulating foil (black colour) in ICP using miller forceps

27
Q

What can be done to adjust high spots on the occlusion of the crown

A
  • Using a large flame shaped diamond bur in an air rotor or speed increasing handpiece
28
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Posterior teeth should hold the shim stock (articulating foil) firmly, whilst the anteriors only hold them lightly

29
Q

Besides the high spots of the occlusion on crowns, what else should be checked

A

The contacts in excursions should also be check and any non-working interferences should be removed

30
Q

AY BAWS CAN I HABE ANODA NOTE PLZ

A

Take care not to overcorrect occlusion boi!!

31
Q

What is used in the finishing and polishing of gold crowns

A
  • Finshing burs followed by rubber abrasive points and white stones
  • Use so flex discs for proximal surfaces
32
Q

What is used in the finishing and polishing of MCC or All-ceramic crowns

A
  • Soflex discs
  • Composite finishing diamonds
  • Rubber abrasive points
  • Lastly use a rubber cup wit diamond paste
33
Q

What are the indications for the use of Zinc Phosphate Cements

A
  • Single metal or Metal-ceramic crowns, Lithium Disilicate, Zirconia crowns with retentive design features
  • Fixed-partial metal-ceramic dentures
  • Posts - material of choice due to slight post-set expansion
  • Multiple cementations

(Same as Polycarboxylate cement)

34
Q

What are the advantages of Zinc phosphate cement

A
  • Longest track record
  • high compressive strength
  • Low film thickness
  • reasonable working time
  • Resistant to water dissolution
35
Q

What are the disadvantages of Zinc phosphate cement

A
  • Low tensile strength (preparation geometry v important)
  • No molecular adhesion to tooth or crown material
  • Not resistant to acid dissolution
  • Powder/Liquid ratio and mixing technique v important for its material properties
36
Q

What are the indications for the use of Polycarboxylate cement

A
  • Single metal or Metal-ceramic crowns, Lithium Disilicate, Zirconia crowns with retentive design features
  • Fixed-partial metal-ceramic dentures
  • Posts - material of choice due to slight post-set expansion
  • Multiple cementations

(Same as Zinc Phosphate cement)

37
Q

What are the indications for the use of Glass Ionomer Cement

A
  • Single metal or metal-ceramic crowns
  • Fixed-partial metal-ceramic dentures
  • Patients with high risk caries
38
Q

What are the advantages of using Glass-Ionomer Cement

A
  • High compressive strength
  • Low film thickness
  • Reasonable working time
  • Fluoride release
  • Forms considerable bond to tooth tissue
  • After setting, resistant to water dissolution
  • High compressive strength
39
Q

What are the disadvantages of using Glass-Ionomer Cement

A
  • Sensitive to early moisture contamination (protection of margins)
  • Low tensile strength
  • No molecular adhesion to crown material
  • Not resistant to acid dissolution
40
Q

What are the indications for resin-modified glass-ionomer cements

A
  • Single metal or metal-ceramic crowns and partial fixed dentures when preparation geometry is borderline
  • Currently not recommended for ceramic crowns, onlays or veneers
41
Q

What restorations are there that resin-modified glass-ionomer cements not recommended for

A
  • Ceramic crowns
  • Onlays
  • Veneers
42
Q

What are the advantages of using resin-modified glass ionomer cements

A
  • High compressive and tensile strength
  • Reasonable working time
  • Low film thickness
  • Fluoride release
  • Molecular adhesion to tooth
  • Resistant to water dissolution
43
Q

What are the disadvantages of using resin-modified glass ionomer cements

A
  • Short track record

- Water absorption causes expansion and cracking of overlying ceramic

44
Q

What are the indications for resin cements

A
  • Porcelain veneers
  • Ceramic, Zirconia and composite onlays
  • Ceramic, Zirconia crowns or fixed-partial dentures
  • Resin-bonded metal bridges
  • Metal, metal-ceramic crowns, Zirconia and FPD with sub-optimal preparation geometry
45
Q

What are the advantages of resin cements

A
  • High compressive and v high tensile strengths
  • Resistant to water and acid dissolution
  • Molecular adhesion to tooth and crown material
46
Q

What are the disadvantages of resin cements

A
  • Highly technique sensitive
  • Variable film thickness
  • Variable difficulty removing proximal and sub gingival excess material
  • Marginal leakage due to polymerisation shrinkage
  • Post-op sensitivity varies with materials and technique
47
Q

When should definitive cementation be postponed

A

If the tooth is symptomatic and the tooth should be monitored

48
Q

What is a key tip to have successful cementation

A

Try to achieve a thin cement film at appropriate compressive strength

49
Q

What is are the essential cementation steps before you seat the crown

A
  • Isolate preparation and ensure good moisture control
  • Clean crown and put aside
  • Clean preparation
  • etch and bond if appropriate
  • Mix cement
  • Coat the fit surface (preferably marginal region) with cement - DO NOT OVERFILL
50
Q

Describe the technique for seating the crown

A
  • Seat crown quickly with firm finger pressure until all excess flows from margins and complete seating
  • Check accuracy of fit using a sharp probe and burnish gold margins before setting of cement
  • Maintain adequate moisture control until complete set of cement
51
Q

How is pressure maintained when seating the crown

A

Either by the dentist or the patient biting on cotton roll for about a minute

52
Q

What steps should be taken after seating the crown

A
  • Excess cement should be removed for conventional cements after setting
  • Excess cement should be removed before setting for resin-based cements
  • Recheck occlusion and adjust if required
53
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

Make sure to floss contacts and check occlusion again after the cementation of the crown

54
Q

What preparation is there for metal crowns before cementation

A

sandblasting the fit surface - i think this cleans is and makes it prepped for cementation

55
Q

What preparation is there for Indirect composite and glass ceramic crowns and restorations

A

HF acid etch

Fixed Prosthodontics (11 decks)

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