Composite Flashcards
15 factors which can go wrong when placing composite
- The wrong Patient - have high caries amount/risk
- The wrong tooth
- Isolation
- Removing the (restoration) caries
- Designing the cavity
- Managing the dentine/pulp complex
- Matrix application
- Contact point
- Etching
- Washing
- Drying
- Lining
- Primer application
- Wet & dry surfaces
- Bonding
- Placing & Handling material
- Curing
- Finishing and polishing
- Occlusal considerations
- Post operative advice
6 factors we need to consider when placing composite
- tooth biology
- materials science
- interfaces
- marginal seal
- manipulation
- polymerisation
all interlined
what will happen if caries remains at ADJ?
result in unsupported enamel and early breakdown of restoration margin (interstitial enamel failure) if micro-leakage occurs as marginal integrity is compromised
why do we need a hybrid layer?
so resin can penetrate the freshly cut dentine
what type of dentine is the poorest to bond to?
tertiary
- occluded tubules
- more mineralised/contaminated
- irregular tubules
when contracts/shrinks restoration more likely to fail
things to consider when preparing dentine
- Removal of smear layer
- Creation of Hybrid layer
- Dentine physiology
- Peri/inter tubular
- Tubule size
- Tubule density
- Water content
- Water transport
- Sclerosis
- Intertubular dentine
- Dead tracts
- Tertiary dentine
- Restorative materials
characteristics of older dentine
- fewer tubules
- more mineralised
- occluded tubules
characteristics of deeper dentine
- water
- more mineralised
- more tubules
basics of how resin bonds to dentine tubules
resin penetrated down tubules
strength from in-between network bonds composite to the solubilised dentine by a layer of resin
characteristics of poor dentine for bonding
- smear layer modified
- solubilised surface
- water content
- resin modified GI
how is adhesion allowed?
through mineral and ion exchange
4 reasons for lining placement
- Effect on bonding
- Enamel contamination
- Protection of pulpal therapeutic agents
- Risks if microleakage occurs
what is the purpose of a lining?
intermediary between poor quality dentine and enamel
- Turning it into good quality bonding material as can etch glass ionomer
Bonds to dentine in different way so can bond to tertiary dentine
factors that can lead to secondary caries
- Dead tracts
- Secondary dentine
- Tertiary dentine
- Sclerosis
- Calcification
what are the 5 commonest problems that can be encountered when preparing a dentine bond?
- cavity preparation (failure to remove all caries)
- bonding (successful? followed instructions?
- contacts (good contact with adj tooth after material contracts? food get stuck?)
- placement (cured?)
- countering contraction stresses (put pressure on rest of tooth on contraction)
what is a bonding interface?
where restorative material meets tooth
what is the best seal?
marginal
what are factors to consider when optimising interfaces?
- Material properties
- Cavity design
- Matrices
- Manipulation
- Configuration factor
- polymerisation contraction stress
what is the most important factor to consider when optimising interfaces?
configuration factor and polymerisation contraction stress
configuration factor
Defined as the ratio of bonded to unbonded surfaces: Important for Composite restorations
what does high configuration factor lead to?
increased polymerisation contraction stress
what does low configuration factor lead to?
reduced polymerisation contraction stress
what is plastic deformation?
polymerisation contraction shrinkage on the surface that is not bonded
- material shrinks
do we want plastic deformation?
yes
what is air inhibition?
when exposed to air only get a small amount of polymerisation due to oxygen inhibition
plasticity
property of a material to undergo a non-reversible change of shape in response to an applied force (polymerisation)
deformation
change in shape due to an applied force (polymerisation)
factors that affect the nature of dentine
- type (1, 2, 3)
- intra/inter/peri tubular
- diamter
- density
- contents/mineralisation
- health/ diseased/ reactive
what is the point of matrix?
way of rebuilding a missing wall of tooth
how does a matrix work?
- Separates the tooth using periodontal membrane
- Composite bigger than need to be
- Shrinks and contacts maintained - nature of material not taken into account
6 steps in clinical procedure
- Etch
- Prime - Etch and prime both done by phosphoric acid (10 on enamel; Another 10 seconds on dentine and enamel)
- Bond (Bonding agent hybrid layer)
- Placement
- Characterisation
- Finish (Shrink 1-2%)
how to minimise contraction stress?
don’t want to bond 2 surfaces together so that they pull together so place in increments
why do you place a small increment of floor of cavity only?
deformation area so bond good
- small bit of composite can deform before large placement
what is important to check when curing?
have the right wavelength for the material - check
Minimum intensity required to adequately cure 1.5 to 2 mm of composite resin is between 280 and 300 mW/cm2
what are 5 different curing regimes?
- Soft Start
- Ramp
- Pulse
- Boost
- Delayed curing
when do you use high power curing?
for fast set
when do you use low power curing?
for close to pulp
when do you use soft start curing?
for polymerisation with reduced contraction stress
slow cure start and then increase in power
what does uncured composite layers lead to?
pain
what is the main reason for reduced shrinkage?
is decreased final conversion
what determines shrinkage direction?
bonded surfaces and free surfaces
when do composites shrink towards the light?
when bonding fails
what is in composites that allows it to be light cured?
Camphorquinone exposed to light initiates polyermisation chain process
what can be used to cover poor quality dentine?
resin modified glass ionomer
what are the properties of flowable compoiste?
can shrink more than other composties
- relieves stress
- poorer bond strength
used as interface to relieve stress
why do you need to cure after polishing and seal?
to prevent sticking feeling when patient leaves
