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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
When is the occlusion checked for a crown
Occlusion should always be the first and last to be checked
26
How can you mark the high spots of the occlusion on a crown
With GHM articulating foil (black colour) in ICP using miller forceps
27
What can be done to adjust high spots on the occlusion of the crown
- Using a large flame shaped diamond bur in an air rotor or speed increasing handpiece
28
AY BAWS CAN I HABE DE NOTE PLZ
Posterior teeth should hold the shim stock (articulating foil) firmly, whilst the anteriors only hold them lightly
29
Besides the high spots of the occlusion on crowns, what else should be checked
The contacts in excursions should also be check and any non-working interferences should be removed
30
AY BAWS CAN I HABE ANODA NOTE PLZ
Take care not to overcorrect occlusion boi!!
31
What is used in the finishing and polishing of gold crowns
- Finshing burs followed by rubber abrasive points and white stones - Use so flex discs for proximal surfaces
32
What is used in the finishing and polishing of MCC or All-ceramic crowns
- Soflex discs - Composite finishing diamonds - Rubber abrasive points - Lastly use a rubber cup wit diamond paste
33
What are the indications for the use of Zinc Phosphate Cements
- 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
What are the advantages of Zinc phosphate cement
- Longest track record - high compressive strength - Low film thickness - reasonable working time - Resistant to water dissolution
35
What are the disadvantages of Zinc phosphate cement
- 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
What are the indications for the use of Polycarboxylate cement
- 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
What are the indications for the use of Glass Ionomer Cement
- Single metal or metal-ceramic crowns - Fixed-partial metal-ceramic dentures - Patients with high risk caries
38
What are the advantages of using Glass-Ionomer Cement
- 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
What are the disadvantages of using Glass-Ionomer Cement
- Sensitive to early moisture contamination (protection of margins) - Low tensile strength - No molecular adhesion to crown material - Not resistant to acid dissolution
40
What are the indications for resin-modified glass-ionomer cements
- 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
What restorations are there that resin-modified glass-ionomer cements not recommended for
- Ceramic crowns - Onlays - Veneers
42
What are the advantages of using resin-modified glass ionomer cements
- High compressive and tensile strength - Reasonable working time - Low film thickness - Fluoride release - Molecular adhesion to tooth - Resistant to water dissolution
43
What are the disadvantages of using resin-modified glass ionomer cements
- Short track record | - Water absorption causes expansion and cracking of overlying ceramic
44
What are the indications for resin cements
- 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
What are the advantages of resin cements
- High compressive and v high tensile strengths - Resistant to water and acid dissolution - Molecular adhesion to tooth and crown material
46
What are the disadvantages of resin cements
- 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
When should definitive cementation be postponed
If the tooth is symptomatic and the tooth should be monitored
48
What is a key tip to have successful cementation
Try to achieve a thin cement film at appropriate compressive strength
49
What is are the essential cementation steps before you seat the crown
- 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
Describe the technique for seating the crown
- 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
How is pressure maintained when seating the crown
Either by the dentist or the patient biting on cotton roll for about a minute
52
What steps should be taken after seating the crown
- 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
AY BAWS CAN I HABE DE NOTE PLZ
Make sure to floss contacts and check occlusion again after the cementation of the crown
54
What preparation is there for metal crowns before cementation
sandblasting the fit surface - i think this cleans is and makes it prepped for cementation
55
What preparation is there for Indirect composite and glass ceramic crowns and restorations
HF acid etch

Fixed Prosthodontics (11 decks)

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