Principles of Composite Restorations - Sturdevant's Ch 8 and Ch 9 Flashcards
List the 7 advantages of composites:
- esthetics
- Conservative in tooth structure removal
- Less complex when preparing the tooth
- Insulating (low thermal conductivity)
- Used universally
- Bonds to tooth structure
- repairable
List the 5 disadvantages of composites:
- May have a gap formation (on the root surface or improper insertion)
- More difficult, tim-consuming, and costly as compared to amalgams (multiple steps & polishing)
- Technique is more important
- May exhibit greater occlusal wear
- Has a higher LCTE (linear coefficient of thermal expansion) = results in potential marginal percolation
If a void or defect is detected before finished, do you have to start over?
No, more composite can be added directly to the void IF the composite has NOT been contoured.
The materials bond because the void area has an oxygen-inhibited surface layer that permits composite additions.
Contouring removes this oxygen-inhibited layer and thus the material would need to be re-etched before placing more composite.
Define over-contouring the restoration
The contours are too high (think: over = higher). The contours created are too large or too occlusal.
Define under-contouring the restoration
The contours are smaller than ideal (think under = small). The contours created are too small or too gingival.
What does RMGI stand for?
Resin Modified Glass Ionomer!
What is flash?
The thin portion of composite extending beyond the margin.
Overcontour
Too much has been added to the restoration
Overflow
The same as flash: composite that has extended beyond the margins.
Undercontour
Too little has been added to the restoration, so there is a little divot.
What is a common polymeric matrix component for composites?
Bis-GMA
Als0:
UDMA
TEG-DMA
Bis-EMA
What are common filler particles for composites?
Glass: barium or borosilicate
Zirconium oxide, aluminum oxide, silicone dioxide
What is used as a coupling agent in composites?
Silane - an adhesion filler to the matrix
What is used as the initiator for composites?
Camphoroquinone - a photoinitiator
Is a composite’s thermal expansion greater or lower than tooth structure’s?
Greater! Composite has a thermal expansion 2-6 times greater than tooth structure.
What size of filler are macrofill composites?
8 micrometers
What size of filler for microfill composites?
0.01 - 0.04 micrometers
What size of filler do hybrid composites contain?
Can have microhybrid or nanohybrid.
Range from 0.4 - 1 micrometers
What size of filler for nanofill composites?
1 - 100 nanometers
What are the general steps for dental bonding?
- Conditioner (etching)
- Primer
- Adhesive
What is the conditioner used for dental bonding?
The etching material.
An acid (phosphoric) that removes inorganic material.
What is the primer used for dental bonding?
A hydrophilic monomer
What is the adhesive used for dental bonding?
A hydrophobic low viscosity resin.
Creates micromechanical retention and is light cured.
How does OptiBond Solo Plus in our clinic work for dental composite bonding?
The primer and adhesive are combined into one step, so it is just a 2-step etch and rinse process.
- Conditioner
- Primer + adhesive
When are retention grooves necessary?
Mainly just in Sim Clinic because we do not use bonding to the plastic teeth.
What are the different types of initiators that may be used for different composites?
Initiators create free radicals:
Heat
Chemical
UV Light
Visible Blue Light
What is irradiance?
Power per area (mW/cm^2)
Basically, how intense and focused the light is.
What is collimation?
The dispersion of the light. A “good” light has good collimation - it is focused and not dispersed.
How long do we cure our composite for?
At lease 20 seconds.
What are 3 main ways to compensate polymerization shrinkage?
- Incremental placement (1 - 2 mm increments)
- Adequate bonding technique
- Placement of a liner
What is the C-factor?
The configuration factor.
Bonded Surfaces/#Unbonded Surfaces
Low C factor = low risk of contraction
High C factor = high risk of contraction
What is the C-factor for a Class I?
bonded surfaces = 5
unbonded surfaces = 1
C-factor = 5 = high risk of contraction
What components are necessary to form a composite material?
Polymeric matrix
Filler particles
Coupling Agent
Initiator
What are the mechanical characteristics of composites (in terms of wear, toughness, and elastic)?
Pretty good wear resistance (though amalgam is better)
Low fracture toughness as compared to metallic
High degree of elastic deformation
Is there any shrinkage with composites?
Yep: 2.6% - 7.1%
What is the coefficient of thermal expansion of composite as compared to enamel?
Composite thermal expansion is 2 - 6 times greater than enamel.
What are the three classifications of composites?
Conventional - more filler, better mechanical properties
Flowable - less filler, less strong
Packable - not recommended.
What are advantages and disadvantages of microfill composites? Give a brand example.
Pro:
Excellent polish
Excellent longevity
Excellent handling
Cons:
Weaker mechanical properties
Not for stress-bearing restorations
Types: Durafil VS (Kulzer)
Renamel (Cosmodent)
What are advantages and disadvantages of hybrid composites? Give a brand example.
Pro: Good polishing Good handling Good physical properties Good range of opacities Excellent longevity
Types:
Premise (Kerr) - microhybrid
Esthet-X HD (Dentsply) - nanohybrid
What are advantages and disadvantages of nanofill composites? Give a brand example.
Pros: Excellent, long lasting polish Good handling Excellent mechanical properites Good for incisal edges Highly translucent Good opacity Excellent longevity
Types: Fitek Supreme Plus (3M) Estelite Omega (Tokuyama)
What can go wrong as a composite restoration is completed?
- Not curing long enough
- Blood or saliva contamination
- Desiccation - creates collapsed collagen fibers and poor bonding
Poor bonding can cause post-op sensitivity
How is OptiBond Solo Plus system applied - the conditioner?
Recall: 1st use the conditioner, rinse, and 2nd use the primer and adhesive combined.
The conditioner:
- Can be used on both dentin & enamel
- Surfaces must be dry
- Do not apply for longer than 15 minutes for dentin
- Rinse thoroughly with water
- Leave the dentin surface damp
How is OptiBond Solo Plus applied - the primer/adhesive combo?
The primer/adhesive combo:
- Apply thin coat
- “Air thin” the solution for 3 seconds to spread and avoid any pooling
- Light cure for 20 seconds
For polymerization, if the initiator is heat, what is the chemical reaction?
Benzoyl peroxide + heat = free radical
For polymerization, if the initiator is chemical, what is the chemical reaction?
Benzoyl peroxide + tertiary amine = free radical
For polymerization, if the initiator is UV light, what is the chemical reaction?
Benzoin methyl ether + 365nm UV light = free radical
For polymerization, if the initiator is visible blue light, what is the chemical reaction?
Camphoroquinone + tertiary amine + 468nm blue light = free radical
When using the Tungsten Halogen (QTH) to apply blue light for polymerization, how long must it be applied?
20 - 40 seconds (500 - 1000 mW/cm2)
When using the High Intensity TH to apply blue light for polymerization, how long must it be applied?
20 seconds (1200 mW/cm2)
When using the Plasma Arc Curing (PAC) to apply blue light for polymerization, how long must it be applied?
10 - 20 seconds (1600 - 2000 mW/cm2)
When using the LED to apply blue light for polymerization, how long must it be applied?
10 - 40 seconds (500 - 1600 mW/cm2)
What type of curing light do we use in clinic?
LED curing light
Ultradent - VALO Curing Light
20 second cure time
What is the range of wavelengths for blue light?
450 - 500 nm
Does it matter how far the light is held from the composite resin as it cures?
Yes. The times were calculated based on the light being 1 - 1.5 mm from the composite resin.
Blue light is pretty. Can we stare at it?
No! Bad for your eyes - cumulative retinal injury.
