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BDS 2 OSCE > DMS > Flashcards

DMS Flashcards

1
Q

What is the smear layer?

A

An adherent layer of organic and inorganic debris - remnant of the dentine surface after preparation of the dentine

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2
Q

Describe self etch

A

Incorporates the smear layer
1 stage
Uses Scotch bond I

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3
Q

Describe total etch

A

Removes the smear layer in 2 stages:
Etch
Prime and bond

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4
Q

How is the hybrid layer formed?

A

37% phosphoric acid etch removes the smear layer exposing the collagen network
Primer penetrates collagen network making the surface hydrophobic
Adhesive resin forms micro mechanical adhesion with tubules and exposed collagen network

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5
Q

What products are found in composites?

A 
Resins
Camphorquinone
Low weight methacrylates 
Silane coupling agents
Filler particles
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6
Q

What resin is commonly found in composite?

A

Bis-GMA

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7
Q

What is camphorquinone?

A

A blue light photoinitiator

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8
Q

What role do low weight methacrylates play in composite?

A

Improves viscosity and reactivity

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9
Q

What role do silane coupling agents play in composite?

A

Provides good bond between filler particles and resin

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10
Q

What filler particles are commonly used in composite?

A

Glass

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11
Q

What reaction takes place in the setting of composite?

A

Free radical addition polymerisation

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12
Q

What are the advantages of light cured composite?

A 
Extended working time
Less finishing
Can be finished immediately
Less waste 
Less porosity
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13
Q

What are the disadvantages of light cured composite?

A 
Absorption/light spectrum mismatch
Cure prematurely under dental light
Depth of cure is optimistic
Polymerisation shrinkage can occur
Recommended setting times may be too short
Ocular damage
Soft tissue damage
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14
Q

What is the depth of cure of composite?

A

2mm

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15
Q

What is the bond strength of composite?

A

40MPa

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16
Q

Give some advantages of using composite

A 
Strong - 350MPa
Rigid - 15GPa
Abrasion resistant
Low thermal conductivity
Can be light cured on demand
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17
Q

What liquid is used in amalgam?

A

Mercury

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18
Q

What are the powder constituents of amalgam and why is each element used?

A 
Tin - intermetallic compound
Silver - intermetallic compound
Zinc - scavenger (removes impurities)
Copper - increased strength and hardness
Mercury - increases rate of reaction
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19
Q

What are the different types of amalgam particles?

A

Lathe-cut

Spherical

20
Q

Describe the amalgam setting reaction

A

Powder and liquid react to form the amalgam matrix (Gamma-1 and Gamma-2) alongside unreacted particles (Gamma)

21
Q

Describe Gamma, Gamma-1 and Gamma-2

A

Gamma - strong, corrosion resistant
Gamma-1 - not strong, corrosion resistant
Gamma-2 - not strong, not corrosion resistant

22
Q

Describe copper enriched amalgam

A

Contains more than 6% copper

No Gamma-2 phase

23
Q

What are the advantages of copper enriched amalgam?

A

Increased strength
Increased corrosion resistance
Higher marginal integrity
Less creep

24
Q

What are the advantages of amalgam?

A 
Strength - 500MPa
Abrasion resistant
Viscosity ideal for packing
Radiopaque
Okay working time
25
What are the disadvantages of amalgam?
``` Poor aesthetics Not anti cariogenic Experiences creep Corrosion Microleakage can occur ```
26
Describe creep
Repeatedly stressed for a long time This results in flow and permanent deformation Amalgam sits proud of the surface and vulnerable to fracture
27
Who should amalgam not be used on?
Children under 15 Pregnant women Breastfeeding women
28
What do cavity lining materials allow protection from?
Unreacted chemicals Thermal stimuli Bacteria and endotoxins
29
What are the ideal properties of a cavity lining material
``` Low thermal conductivity Thermal expansion coefficient similar to dentine High compressive strength Radiopaque Low solubility Cariostatic Biocompatible ```
30
What are the most common lining materials?
Calcium hydroxide | GI and RMGIC
31
What is GI made up of?
Acid - polyacrylic acid and tartaric acid | Powder - Mainly silica
32
What are the setting phases of GI?
Dissolution Gelation Hardening
33
Describe Dissolution of GI
Acid is added to solution H ions attack the glass surface Ca, Al, Na and F ions are released Left with silica gel around unreacted core particle
34
Describe Gelation of GI
Calcium ions released are bivalent so cross linking occurs | Polyacrylic acid reacts with carboxyl groups to form calcium polyacrylate
35
Describe Hardening of GI
Trivalent aluminium ions cross link to increase strength This forms aluminium polyacrylate Starts after 30 minutes and can last up to a week
36
What is RMGIC made up of?
Powder - Glass | Acid - Polyacrylic acid, tartaric acid, HEMA (monomer), water
37
Describe the setting reaction of RMGIC
Acid base reaction takes several days Redox reaction takes 5 minutes Free radical polymerisation reaction (light activated) takes 20 seconds
38
What are the advantages of GI?
``` Release flouride Forms chemical bond to enamel and dentine Little microleakage occurs Good thermal properties No contraction on setting ```
39
What are the disadvantages of GI?
``` Brittle Poor wear aesthetics Poor handling characteristics Poor aesthetics - opaque Moisture dependant ```
40
What are the advantages of RMGIC?
``` Releases flouride Forms a chemical bond to enamel and dentine Little microleakage occurs Better physical properties than GI Better handling properties than GI Lower solubility than GI Better translucency and aesthetics Stronger ```
41
What are the disadvantages of RMGIC?
Polymerisation contraction takes place Monomer leaching - uncured HEMA can be toxic to the pulp Reduced strength from uncured material Exothermic acid base reaction Swelling due to uptake of water due to HEMA
42
What is used clinically as a setting calcium hydroxide liner?
Two pastes - a base and a catalyst | eg - Life or Dycal
43
When is Zinc Oxide Eugenia Cement used?
Linings in deep cavities Temporary restorations Root canal sealer Periodontal dressing
44
What are the properties of ZOE?
``` Adequate working time Relatively rapid setting time Low thermal conductivity Low strength Radiopaque High solubility ```
45
What are the properties of calcium hydroxide?
``` Quick setting time Radiopaque Easy to use Low compressive strength Unstable and soluble ```
46
What should be done after placing a calcium hydroxide lining?
Should be covered with RMGIC prior to a final restoration being placed to protect the calcium hydroxide and prevents its dissolution
47
What glass ionomer is used clinically?
Vitrebond

BDS 2 OSCE (24 decks)

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