Composite Flashcards
Why is longevity of a restoration important
we do not want to remove the restorations that we make as when we remove/replace a restoration we increase the risk of damaging the pulp and root canal as well as removing more healthy tooth tissue
what is the most long lasting restoration
gold
what are the 15 reasons a restoration can fail
The wrong patient The wrong tooth Isolation Removing the caries Designing the cavity Managing the dentine/pulp complex Matrix application Contact point Etching Washing Drying Lining Primer application Wet and dry surfaces Bonding Placing and handling materials Curing Finishing and polishing Occlusal considerations Post-operative advice
how can the patient affect the longevity of a restoration
if a patient is at high risk of caries because of their diet and other factors then it is more likely that their restoration will fail
what do we need to consider in terms of marginal integrity in regards to enamel
prism orientation
occlusion
where should we avoid cavosurface margins
in areas of occlusal contact
what will caries at the ADJ result in
unsupported enamel
early breakdown of restoration if micro leakage occurs
what is microleakage
diffusion of the bacteria, oral fluids, ions and molecules into the tooth and the filling material interface
why does poor enamel preparation allow micro leakage
. Poor enamel preparation results in rough surfaces and these rough surfaces have small cracks in them and these small cracks of unsupported enamel can later result in a fracture which can allow microleakage
what does a white line around the edge of a restoration indicate
we are looking at early failure of the restoration as this indicates an enamel fracture.
what does primary dentine consist of
fresh, open tubules
what does tertiary dentine result in
irregular structure
not great to bond to
what are factors that effect the bond
Removal of smear layer Creation of hybrid layer Dentine physiology Peri/intertubular Tubule size Tubule density Water content Water transport
what is deeper dentine like
wetter
more mineralised
contains more tubules
what is older dentine like
fewer tubules
more mineralised
occluded tubules
what does poor dentine consist of
Dead tracts Secondary dentine Tertiary dentine Sclerosis Calcification
what is a lining for
When there is poor quality dentine we use resin modified glass ionomer which allows adhesion through ion exchange
what does the lining protect
pulp
what are the commonest issues when it comes to composite
cavity preparation bonding contacts placement countering contraction stresses
describe issues related to cavity prep
sometimes we have failed to remove all the caries and this can result in a poor bond
describe issues related to contacts
If the tooth contracts then these contact points open up and the patient complains of food getting stuck between their teeth.
describe issues relating to placement
sometimes not all the material will be cured.
describe issues related to contraction stresses
if the material is successfully bonded to the tooth and shrinks slightly then this will put a lot of pressure on the rest of the tooth and restoration, the tooth will have tension
what are the 2 biggest factors that need considered when preparing/fixing a filling
Configuration factor
Polymerization contraction stress
what is the configuration factor defined as
the ratio of bonded to unbounded surfaces
what does a high configuration result in
increased polymerization contraction stress
what does a low configuration factor result in
reduced polymerization contraction stress
what is polymerization contract shrinkage
movement of the material as there is a change in dimension of the material
where do we want deformation to happen
surface that is not bonded
what is the volumetric change dependent on
how much monomer make up the polymer
what is plasticity
property of a material to undergo a non reversible change in shape in response to an applied force
what is deformation
change in shape due to an applied force
what happens if there is a poor bond in the base of the cavity
there is deformation is on the bonded surface and a gap appears
The gap fills with dentinal tubular fluid and when the patient is eating the forces will cause a change in shape and the dentinal fluid will move up and down causing sensitivity.
what do we use to make better contacts for inter proximal restorations
matrixes
how do matrices work
They separate the tooth using the periodontal membrane and so when the restoration shrinks the contact point is preserved
what is the clinical procedure
- Etch – need to etch enamel surface
- Prime – need to prime dentine surface
- Bond
- Placement
- Characterization
- Finish
where do we consider flowable composite
floor of the cavity to mediate contraction stresses on the interface to achieve optimal adaption to non load bearing margins
how do we apply composite
in increments
describe how we apply increments
- First increment – floor only. This is a reservoir for plastic deformation.
- The successive increments should touch as few surfaces as possible so that we don’t pull the walls to the center
- The final increments do not join enamel margins
what is the minimum intensity required to adequately cure 1.5 to 2mm of composite resin
280 and 300 mW/cm2
what are the curing regimes
soft start ramp pulse boost delayed curing
what is the polymerization of all materials due to
halogen like emission spectrum
380-515nm
what causes the polymerization
camphorquinone
how does camphorquinone work
causes the polymerization as when exposed to a certain wave length it releases free radicals which initiate the polymerization process
Removing a composite filling can be difficult due to how similar it looks to the natural tooth - what can be done to help differentiate?
if you etch the tooth and the filling - the restoration should be a diff color and the tooth chalky white which can therefore help the dentist differentiate and decide where to begin
- use air abrasion unit that uses aluminum oxide powder which can selectively remove composite and retain solid enamel
