DMS Summary Flashcards
What are the principles of cavity prep (6)
- Identify and remove carious enamel
- Identify max extent at ACJ
- Remove peripheral caries then circumferentially deeper
- Remove deeper caries over the pulp
- Outline form modification
- Internal design modification
Name some advantages of composite (5)
- Aesthetics
- Bond to tooth
- Command set
- Conserves tooth tissue
- Low thermal conductivity
What is the c factor
Ratio of bonded to unbonded SA
List some properties of composite
Radiopaque
Low setting shrinkage
Low thermal conductivity
Bonds to tooth
Biocompatible
High strength
What is composite composed of?
Filler - glass quartz
Resin - bis GMA
Photoinitiator - campherquinone
Low weight dimethacrylate - TEGDMA
Silane coupling agent
Different types of filler particles (3)
Conventional
Hybrid
Microfine
Function of resin bisgma
Undergoes free radical addition polymerisation
Difunctional molecule to allow c=c cross linking
Function of initiator
Produces free radicals
Function of silane coupling agent
Allows glass to bond to resin
Methoxy group reacts with absorbed water
Clinical factors that affect wear of composite (5)
Placement
Curing
Finishing
Occlusion
Cavity size + design
What is amalgam made of?
Liquid - mercury
Powder - copper, silver, tin, zinc
What are the types of particles in amalgam?
Lathe cut
Spherical
Setting reaction for amalgam
Powder + liquid –> unreacted particles + amalgam matrix
Unreacted zinc potential issues
Reacts with saliva/blood
Forms zinc oxide + H bubbles = increased pressure expansion of AM
or
decreased pressure = pulpal pain
List some properties of amalgam
High thermal conductivity
Corrosion
Longer handling
Not moisture sensitive
Cheaper
Worse aesthetics
Mercury toxicity
Mechanical retention required
Constituents of GI (2)
Powder
- Silica
- Alumina
Liquid
-Polyacrylic acid
- Tartaric acid
3 phases of the acid/base setting reaction for GI
- Dissolution
- Gelation
- Hardening
What happens at dissolution phase?
H ions diffuse into glass
What happens at gelation phase?
Ca ions crosslink
Initial set of GI
What happens at hardening phase?
Continued cross linking
Can last 7 days
What can happen if there is contamination during setting?
Al ions diffuse out material
Water absorbed from saliva/blood
Constituents of RMGI
Powder (barium glass)
Liquid (HEMA, tartaric acid, polyacreyic acid, photo initiator)
Setting reaction for RMGI
Dual curing - acid base
Tri curing - redox
Name 3 examples of liners
CaOH
ZOE
RMZOE
How does CaOH work to protect pulp
Bacteriocidal (alkaline)
Imitates odontoblast layer
–> necrosis
–> forms tertiary dentine to protect pulp
When to not use ZOE
Do not use under composite
Inhibits resin set
List some properties of acrylic (denture base)
Dimensionally accurate
High thermal conductivity
Non toxic
Non irritant
Poor mechanical strength
2 types of PMMA
Self cure - URA
Decreased fracture resistance
Light cure - Denture
Increased fracture resistance
List some ideal properties of a denture base (7)
Aesthetics
Cost effective
Non toxic/irritant
Low weight
Dimensionally stable
High thermal conductivity
Flexural strength
Consistuents of PMMA (2)
Powder - PMMA, plasticiser
Liquid - methacrylate, inhibitor
Faults during production of PMMA (acrylic)
Contraction porosity
Gaseous porosity
Granular
Crazing
How do we bond to enamel?
Enamel = hydrophobic + high surface energy
37% phosphoric to roughen enamel + allow micro mechanical interlocking of resin fillers
Improves wettability
Removes contaminants
How do we bond to dentine?
Dentine = hydrophilic + low surface energy
Dentine conditioner
- Etches dentine
- Opens up dentinal tubules and removes smear layer
Primer
- HEMA/MDP, 4META = coupling agents
- Bifunctional with hydrophobic + hydrophilic ends
Adhesive
- Mix of bisGMA+HEMA forms hybrid layer
Give examples of non elastic impression materials
ZOE
Impression compound
Give examples of elastic impression materials
Hydrocolloid
Alginate + agar
Silicones
Polyether
Give examples of elastomer impression materials
Polyether + silicones
Definition of an elastic impression material
Records undercuts
Elastic strain + elastic recovery
Definition of a non elastic impression material
Can’t record undercuts is rigid
Definition of mucostatic material
Fluid material that displaces soft tissues slightly and gives impression of undisplaced mucosa
Definition of a mucocompressive material
Viscous material that records impression under load + takes impression of displaced tissues
Ideal properties of an impression material
- Biocompatible
- Non toxic/irritant
- No thermal contraction
- Operator convenient
- 100% elastic recovery
- Unaffected by moisture
What type of material is alginate?
Elastic hyodrocolloid
Constituents of alginate
Sodium alginate
Silicate powder
Calcium phosphate
Advantages of alginate
Sets fast
Cheap
Adequate surface detail
Disadvantages of alginate
Poor dimensional stability
Distortion
Operator dependent
3mm thickness required
What type of material is impression compound?
Non elastic mucocompressive
Advantages of impression compound
Mucocompressive
Good for edentulous
Can alter set
Disadvatanges of impression compound
Mucocompressive - avoid in flabby ridge
Rigid
Poor dimensional stability
What type of material is polyether?
Elastic elastomer - Impregum
Advantages of polyether
Hydrophilic - good for poor moisture control Dimensionally stable
Disadvantages of polyether
Rigid when set - not for undercuts
Difficult to remove
Absorbs water
When are light + medium bodied silicones used?
Crowns bridges dentures
Disadvantage of silicone
Hydrophobic
