composite Flashcards
what is the composition of resin composite?
resin- meth (BISGMA) dimity (TEGMA)
filler- silica based glass
coupling agent- silane
activator- camphorquinone
pigments
what is the purpose of an activator?
- camphorquionone absorbs light at 470nm (visible blue light)
- is a photoinitiator
- yeilds necessary free radicals to initiate free radical addition polymerisation
what is the purpose of filler?
- improves strength
- more opaque
- reduces polymerisation shrinkage and thermal expansion
how are composite resins classified?
- filler size ( macro, micro, nano, hybrids)
- indirect or direct rest
- handling conditions (flowable less viscous/packagble more viscous)
- how its cured- chem/light
what are the advantages of using resin composite?
- good aesthetics
- chemically bonded to tooth- so conservative of tooth tissue
- strong material
- wear resistant
- command set
what are the disadvantages of using resin composite?
- must have excellent moisture control (dental dam)
- polymerisation shrinkage- must be placed in oblique increments - less than 2mm for curing purposes and only touching 1 cavity wall
- brittle in thin sections
- technique sensitive
- prone to staining
- expensive
what is the c factor ?
ratio of bonded to unbounded surfaces- the lower the c factor the more desirable in terms of polymerisation shrinkage
what are the classifications of cavities?
class I- post occlusal cavities and buccal pits
class II- posterior Interproximal cavities
class III- anterior Interproximal cavities not affecting incisal edge
class IV- anterior cavities involving incisal edge
class V- cervical margin cavities of ant/post
also:
root caries
secondary caries
when do you treat class III cavities?
- reached ADJ
- cavitated
- seen of RG
how do you treat class III cavities?
- LA
- take shade with light off
- dental dam placed
- use small round bur- access caries palatally where possible and keep labial intact
- outline form with small round bur- keep minimal as resin bonded to tooth
- leave unsupported enamel
- BEVEL ENAMEL FOR ANTERIORS FOR INCREASED SURFACE AREA FOR ETCH AND BOND- BETTER RETENTION
- remove caries from adj
- remove stained dentine- better aesthetics
- etch/prime/bond
- place matrix strip interdentally
- place composite in increments and cure
- final cure using matrix strip to remove o2 and for better aesthetics
- polish and check for any marginal deficiencies with probe
- check occlusion and contact points with floss
how do you treat class IV cavities?
- LA
- take shade with light off
- rubber dam
- outline form- bevel enamel
- normally tooth build up
- remove caries if necessary
- etch, prime, bond
- place matrix strip
- build dentine core with composite using matrix strip and cure
- use translucent shade for incisal edge with matrix strip and cure
- polish and check occlusion
why use matrix strip for final incremement?
better aesthetics and removes oxygen
how long do you etch, prime, bond, cure ?
etch- 20 seconds
prime-
bond-
cure- 30 seconds
how do you treat class I caries?
always occlusal- caries spreads rapidly laterally along ACJ
- LA
- shade- no light
- dental dam
- outline form- access caries
- NO BEVELLING
- remove caries from adj first
- remove infected dentine
- check cavity feels firm- affected dentine even if stained
- place lining if appropriate
- etch, prime, bond
- place and contour to shape of tooth with flat plastic and cure in increments
- polish and check occlusion
how do you treat class II cavities?
LA
shade
dental dam
- access caries- outline form
ensure contact point has been cleared - remove caries from ADJ
- remove rest of infected dentine
- place matrix band
- line if required
- etch, prime, bond
- place composite in oblique increments, contour and cure
- check margins with probe
- polish as necessary
- check occlusion and contact area with floss
