Finals

• 4 temporary cements

  calcium hydroxide

  glass ionomer

  zinc oxide eugenol

  zinc polycarboxylate
• pros and cons of calcium hydroxide

  - stimulates odontoblast promoting secondary dentine

  - bactericidal

  - promotes remineralisation

  - radio-opaque

  - hard-setting

  
  

  - weak

  - cant dress cavity alone

  - non-adhesive
• reaction of calcium hydroxide

  chelating reaction zinc oxide + butylene glycol salicylate
• names of calcium hydroxide

  dycal

  dropsin

  life

  
  

  1:1 mix`
• pros and cons of zinc oxide eugenol

  - sedative

  - 1st choice in retentive cavities (i.e. lost amalgams)

  - bactericidal

  
  

  - non-adhesive

  - can't use in composite (eugenol effects polymerisation)

  - highly soluble

  - relatively weak
• setting reaction of ZOE

  2x eugenol groups chelate with zinc ions
• examples of ZOE


  kalzinol

  sedanol
• pros and cons of GI

  - strong

  - bonds to enamel and dentine

  - can use in non-retentive cavities

  - aesthetics

  - tight seal

  - no undercuts needed (unless heavy load)

  
  

  - hard to remove

  - deep cavities may need calcium hydroxide

  - good moisture control needed on insert
• composition of GI


  alumino silicate glass and polyacrylic acid
• pros and cons of zinc polycarboxylate

  - permanently cements crowns/bridges

  - bonds to dentine

  - good for non-retentive cavities

  
  

  - very white (poor aesthetics)

  - very acidic

  - irritant to pulp
• name of zinc polycarboxylate

  poly F
• temporary crown cement


  tempbond
• law for temporary cementing and what it says

  dental auxiliaries regulations 1986

  
  

  in 1999- DHT can under direction of the dentist when fallen out during DHT tx

  
  

  in 2000- temp crowns allowed under same provisions as above

  
  

  dental hygienist- must advise to see dentist ASAP as inform dentist

  
  

  dental therapist can restore permanently if px to do so- no need to liaise
• 12 steps for placing temporary cement

  1) locate tooth and lost fill

  2) tell patient of incident + procedure

  3) isolate and dry

  4) remove loose material, LEAVE CARIES (unless px)

  5) wash, dry, inspect

  6) pulp exposure? inform dentist +/- CaOH if emg

  7) select material

  8) mix and place

  9) check occlusion +/- adjust

  10) clear gingival margins

  11) advise pt to contact dentist/ arrange follow up

  12) write up notes
• ready mixed cements


  cavit

  coltosol
• why do we replacing crowns and whats the procedure (13)

  why? maintain position, pulpal health, and aesthetics

  
  

  1) assess but DO NOT alter crown or tooth

  2) identify if can be replaced

  3) remove cement from tooth (hand)

  4) remove cement from crown (hand/slow rotary)

  5) confirm orientation and seating

  6) protect airway

  7) isolate and dry

  8) mix

  9) load and seat

  10) bite on CWR

  11) clear gingival margins and excess

  12) advise pt to contact dentist/ arrange follow up

  13) write up notes
• 5 R's


  review

  refurbish

  reseal

  repair

  replace
• cavity prep for an amalgam features (12)

  - 90 degree cavo-surface angle

  - retention form

  - resistance form

  - flat floors

  - straight walls

  - undercuts, locks, grooves, dovetails (macromechanical)

  - smooth internal and external line angles

  - smooth outline form

  - cleansable margins

  - smooth outline form

  - 1.5mm deep

  - wide enough for plugger
• why is cavo-surface angle important

  obtuse= weak in thin sections will fracture

  
  

  acute= undermined enamel
• why are slots, grooves, undercuts and locks needed?

  amalgam is micromechanical
• resistance form vs retention form

  resistance form= prevents apical or oblique dislodgement by forces

  
  

  retention form = prevents displacement along path of insertion
• 8 steps of cavity preparation

  1) access the cavity

  2) clear peripheral caries at ADJ- consider material

  3) remove undermined enamel

  4) retention and resistance

  5) finish cavity margins (cavo-surface)

  6) treat caries over pulp

  7) cavity toilet

  8) line/restore
• enamel structure


  95% inorganic hydroxyapatite crystals (calcium, phosphate, carbonate, magnesium, sodium)

  4% organic material (soluble and insoluble proteins, peptide, citric acid)

  1% water
• dentine structure


  70% inorganic hydroxyapatite crystals

  20% organic material

  10% water
• what is composite


  organic resin material + inorganic glass filler + coupling agent

  (polymer + ceramic)
• organic resin example and use

  BisGMA

  base monomer, provides structure and viscosity
• example of inorganic filler

  silica, quartz, barium, strontium glass derivatives
• coupling agent example and use

  TEGDMA

  cross-linking resin, allows higher filler content and controls viscosity
• larger denser irregular fillers vs smaller spherical fillers

  larger= more wear resistant

  smaller= more polishable but less wear resistant
• setting reaction of composite

  polymerisation

  
  

  monomers to polymers via LED light
• risk of polymerisation


  shrinkage

  
  

  shorter monomer chains = more need to join = + reduction in space = +shrink
• how does composite bond to enamel

  micromechanically using etch and bond
• use of etch in enamel and dentine

  removes contaminants + smear layer ( layer of in/organic cutting debris)

  
  

  enamel= increases surface bonding area providing micro-irregularities

  
  

  dentine= unblocks/widens tubules, demineralised dentine exposing collagen network in dentine matrix
• risk over over etching and incomplete collagen rehydration, and what is the hybrid zone

  unfilled porosities in hybrid zone causing fluid movement = post of sensitivity and bond degradation

  
  

  hybrid zone= penetration of prime/bond into microspaces providing seal and bond between comp and dentine
• how does composite bond to dentine

  via bonding agent due to the hydrophilic dentine and hydrophobic composite
• use of primer


  enters collagen network

  solvent displaces water then primer enters microspaces around fibrils and rehydrates collagen

  
  

  has a hydrophilic group and resin-linking group
• use of bond


  goes into primer space then comp chemically cross-links to monomers in air-inhibited layer
• resin modified GIC vs polyacid modified composites and their benefits

  RM-GIC = most GIC with added resin

  pros= fluoride release, chemical bonding, +strength and wear, improved handling

  
  

  polyacid modified composites= mainly resin with some GIC, but not enough for acid-base reaction

  pros= some fluoride release, +aesthetics, strength, mechanical performance
• what is a GIC

  alumino-sillicate glass + polyacrylic acid
• composition of GIC


  fluoro-allumino- silicate glass, vacuum dried polyacrylic acid, pigments + distilled water

  
  

  or

  
  

  fluoro-allumino- silicate glass, pigments + polyacrylic acid