Autumn quiz: Composites, curing lights and adhesives Flashcards
what are the 3 general parts to composite
- resins/initiators (make resin polymerize/harden)
- coupling agent (connects resin to filler materials)
- filler (comes in diff shapes/sizes)
what are the qualities of monomer resin
resin are materials that harden as they go from monomers to polymers
monomer resin is:
-weak
-poor wear resistance
-significant shrinkage
-hydrophobic once cured
-polymerization is inhibited by oxygen, this is just a surface phenomenon- finish and polish fixes that. this allows composite to stick to more composite tho..
what are the 3 major monomers resin
bis gma
udma
tegdma
—-> methacrylates?
what are initiators?
name some common ones- general expensiveness?
this is what we light cure to change monomer to polymer.
common ones:
-camphorquinone (CQ) + tertiary amine (cheap.yellowish)
-1-phenyl-1,2-propanedione (PPD)
-2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO)
-Both PPD and TPO are lighter color (better coloring) but more expensive and more restrictive absoprtion range
what does light do to initiators
makes them interact w monomers to make polymers (light within a specific range freq)
describe the chemical process of polymerization of resin monomers
-free radical creation caused by light, breaking down an unstable covalent bond, leaving two interactive/reactive free radicals.
-the free radicals react with double bonds on monomers- chain reaction of polymerization. ends when reactive monomers run out of other unreactive monomers to link with
chains take up less space than monomers- always shrinkage
shrinkage is about 7% if not filled in the hole.???
???
what is dual-cure composite, whats it good for?
dual cure composites- taking two separate composites- one that is light, one that is chemical cured and combing
good for deep cavities and bulk fill (dont want to do in increments)
what is the chem reaction of dual-cure?
one paste has benzoyl peroxide (BP) other has aromatic tertiary amines
-light cure by CQ (camphorquinine)/amine reaction
or will react with benzoylperoxide for chemical cure/amine reaction also
light can penetrate 2 mm, deeper, chemical helps to solidify.
what is silane used for
its a coupling agent
dual sided; one reaction with glass (filler) and the other end has a covalent or organic bond reacting with resin material.
-silane molecules bond resin to filler.
whats the purposes of filler in composite
- improves fracture resistance (biggest one)
- reduces polymerization shrinkage
- impart color and opacity
- improve radiopacity
pretty much all made up of glass/silica
what are the components of filler ?
- glass/quartz (barium oxide glass, ba-al-fluorosilicate, dispersed silica)
- metal oxide (gives opacity, radiopacity, color) typical medals include aluminum, cobalt, chromium, magnesium, silicon and iron..
what are the features of MACROFILL, whats its uses?
around since 1960s
- large and irregular (8-12 micrometers)
- good fracture resistance
- poor polish
- poor wear resistance
- low shrinkage
- horrible old anterior composites (opaque)
- milled
uses: crown build up materials, rockcore?, chemical or dual cure
(aesthetics dont matter, big hole)
whats microfill/whats its uses and features
made in 1970s
- spherical shape for handling and aesthetics (more likely to fracture, higher shrinkage rate)
- colloidal silica particles
- 55% filled
- high polish
- poor fracture resistance
- good wear resistance
- high shrinkage (low fill)
- heat created
- uses; composite veneers, carious or non carious cervical lesions.
whats microhybrid /features and uses
- 1st UNIVERSAL composite, 1880s-90s
- mix of glass and ceramic particles (.6-2 microns)
- 70-77% filled; highly filled!
- low shrinkage
- good polish
- good wear resistance
- uses: universal application, anterior ANd posterior, good range of opacities and shades
whats nanofill/uses and features
- nano clusters
- .001 - .01 microns
- allows DENSE filling with good flow
- increase fill rate without stiffening
whats nanohybrid/uses and features
mix of nano particles with conventional fillers
- highly filled
- good polish
- universal application
- good wear resistance
- low shrinkage
what are universal composites? uses?
also called packable
- what we usually think of. not flowables.
- use on anterior, or posterior, make teeth pretty. we use cur ?
what are flowable composites featuers and uses
lightly filled
- because they are lightly filled, they have higher shrinkage
- good wear resistance
- good adaptation to irregular tooth surfaces
-uses; Liners (deep caries/indirect pulp cap), immediate dentin sealing (IDS), small restorations, class V, repairing provisional restorations
what is build up composite features and uses
- opaque
- dual cured
- uses; post endodontic treatment, large cavitation, idealize tooth for crown prep
what is sealant ?
- VERY low fill (unfilled usually)
- serves as bonding agent and restorative material (just etch and place material)
- protected by tooth anatomy
- flow into narrow crevices
what is wetting resin? & featuresuses?
-UNFILLED
-transparent
-RADIOLUCENT
-uses; ONLY placed on instruments? so stuff doesnt stick to other stuff.
too much will weaken composite?
what type of curing light do we use
VALO.
what are the light peak ranges for the 3 main initiators
CQ; 420-495 (470 nm)
PPD; 390-460 (peak 440 nm)
TPO: 350-430 (peak 410 nm)
whats the ideal curing distance
1 mm from light source to composite (as close as you can get without touching it)
light source should be at 90 degrees to the surface of the composite
what impacts the depth of cure light
- shade
- opacity
- incremental layering (light cant penetrate more than 2 mm)
- bulk fills are not ok to light cure really but theres usually a dual cure component so technically it could…..
what are the 3 modes of valo and what do we use
why dont we cure for too long?
we just use standard
standard ; 1,000 mw/cm^2
High: 1400 mW/cm^2
plasma: 3200 mW/cm^2
- over curing will not damage the composite
- heat can cause pulpitis! 5.5 degrees celsius for more than 10 seconds is bad
whats the 3 tasks for bonding materials
- ETCH; selectively removing “smear layer” and mineral from surface
- PRIME: infiltrate exposed collagen
- BOND: link infiltrated collagen to active resin surface. each ‘generation’ of adhesive achieves tasks in a unique combo
what are the features of enamel bonds/uses?
- consistent/strong and durable
- etch (phosphoric acid) creates enamel tags, removes mineral between rods and removes mineral from ends of crystallites (v good for bonding)
- adhesive resin flows into porosites in enamel surface
- hydrophilic primer not needed
- known as a micromechanical retention
- uses: sealants, diastema closure, orthodontic appliances..
what are the features of dentin bonding
- ionic bonding with resin NOT effective . composite is hydrophobic. hydrophilic ones break down by hydrolysis over time…
- hydrophilic substrate
- no opportunity for covalent bonding
- fires 3 generations: were unsucessful
- unable to overcome stresses of polymerization shrinkage. about 17 mPa
whats total etch; 4th vs 5th gen
both use total etching; etching for enamel AND dentin. then rinse
- 4th: phosphoric acid gel etchant. separate primer used. separate adhesive (bonding agent) used as well
- 5th; phosphoric acid gel etchant. combined primer and adhesive.
what does etching do to dentinal tubules
dentin, collagen, mineral matrix, smear layer
-phosphoric etch removes smear layer completely. collagen is exposed, dentin tubules opened and release some dentinal fluids. rinsed away, left somewhat moist. keeps hydrophilic collagen permeable. resin primer has hydrophilic monomers and solvents, placed on wet surface, solvents wick resin into collagen mesh. surfaces air thinned, dries off remaining water and solvent, ethanol and acetone. this leaves just monomers permeating the mesh.
primer can be light cured at this stage (depends on manufacturer) adhesive is placed on primed surface, resin mingles w primed monomers to form resin mass anchored into collagen , locked in.
-light cure adhesive layer, oxygen inhibited resin layer which will bond well with composite after. composite is placed/light cured. layer of bonded tooth w tooth structure + resin is hybrid layer.
what factors hurt bonding ? which more?
dentin especially but both. enamel isnt as sensitive
contamination: saliva , blood, crevicular fluid, dentinal fluid, humidity
- etching variability: time, location
- moisture; too little= collagen collapse. too much= incomplete placement
whats the effect of OVER etching/drying?
when not enough moisture, collagen collapses. hard to permeate. trapped air.. sensitivity not good
what problems occur with composite/if things are not done right
-biting sensitivity is the most common (immediately after placement. failure of bond on pulpal floor)
-secondary caries; gingival margins on dentin or cementum
-breakdown of bond over time. gingival margins on dentin, spread of caries on pulpal floor.
(class II especially?)
whats self etch 6th/7th gen?
6th generation!!!!!
-acidic primer; replaces phosphoric acid gel, effective on DENTIN but less effective on enamel…. adhesive; equivalent of adhesive in 4th generation , mostly hydrophobic
-7th generation; acidic primer and adhesive in one containe!!!!! May need to be mixed before applying. many have failed miserably!!!!!
describe what the acidic primer does to the dentin
smear layer ‘dissolves’ into the se primer. not washed away but air thinning gets most liquid away.
- place adhesive, flows into remaining resin primer and dentin, light cure/ little or no demineralized collagen should remain without a resin coating.
- composite bonds to adhesive, adhesive should be thicker than primer layer.
whast the rationalconcerns
-rationale; simpler! dont worry about how long you etch or how long its there. less post op sensitivty. elimination of incomplete hybrid layer problem
concern; inferior enamel bond - not as strong of an acid so bonding fails at enamel. water sorption issues; combined ingredients mixed that break down over time into hydrophilic/hydrophobic components, allowing for hydrolysis to occur???
whats selective etch? how is it used/ features
best of both worlds
- acid etch enamel (15 seconds) acid CANT touch dentin.
- some un-etched enamel is better than some etched dentin!!
- etch on dentin will expose collagen that may not be completely perfused//
- rinse for 5 seconds and dry the tooth. amount of moisture is NOT critical
- apply self etching primer (for dentin)
- scrub (10 seconds) and air thin. scrubbing breaks up smear layer and encourages demineralization. air thinning allows maximum amount of clean strong adhesive.
- apply adhesive! unadulterated resin provides strong enamel bond and link to primer in dentin. ?
-light cure for 20 seconds!
what are the 3 etch adhesives good for ?
universal adhesives? except they arent really…..
7th and 8th generations
- self etch; good bond to dentin, mediocre to enamel
- selective etch; preferred method. claims etch on dentin not a problem
- total etch; good enamel bond, claims etched dentin can be perfused whether dentin is left moist or dried. currently recommended for NON CARIOUS CERVICAL LESIONS (NCCLs)
