Material Constituents

Question 0

What are the constituents of alginate and their functions?

Answer 0

Salt of alginic acid (e.g. Na Alg) - 12% - reacts with Ca ions
Calcium sulphate - 12% - provides Ca ions
Tri sodium phosphate - 2% - delays gel formation (controls working time)
Filler - 70% - cohesion, strength
Modifiers, flavourings, chemical indicators - small percentage - improves surface, taste, pH colour change

Question 1

What are the constituents of impression compound and their function?

Answer 1

Resins - 40% - hard when cold
Wax - 6.6% - thermoplastic
Stearic acid - 3.3% - plasticiser
Filler - 50% - reduces stickiness and shrinkage
Pigments - provide colour

Question 2

What are the constituents of ZOE?

Answer 2

Two pastes: ZnO powder + oil (paste, plasticiser)
Eugenol + inert filler (talc, kaolin)
+ accelerator (zinc acetate)
+ hydrogenised rosin (paste, cohesion, accelerator)

Question 3

What are the components of a dental bonding agent? Give an example of each.

Answer 3

conditioner (usually phosphoric acid 30-50%)
primer (bifunctional molecule, hydrophilic to hydrophobic molecule, wetting agent - HEMA, 4-META, MDP)
adhesive (Bis-GMA and HEMA - penetrates hydrophobic surface of primed dentine to form hybrid layer in tubules)

Question 4

What are the components of RMGIC?

Answer 4

liquid = HEMA resin, polyacrylic acid, tartaric acid, water, photo-initiators
powder = fluoroaluminosilicate glass, barium glass, vacuum dried polyacrylic acid potassium persulphate, ascorbic acid, pigments

Question 5

What is the composition of traditional amalgam powder?

Answer 5

70% silver Ag
25% tin Sn
3% copper Cu
1% zinc Zn
1% mercury Hg

Question 6

What are the constituents of heat cured acrylic liquid and their function?

Answer 6

Methacrylate monomer - dissolves PMMA particles - polymerises
Inhibitor (hydroquinone 0.0006%) - prolongs shelf life as it reacts with any free radicals produced by heat/UV light
Co-polymer - improve mechanical properties

Question 7

What are the constituents of heat cured acrylic powder and their function?

Answer 7

Initiator (benzoyl peroxide 0.2-0.5%)
PMMA particles - pre polymerised beads
Plasticiser - allows quicker dissolving of monomer liquid (eg dibutyl phthalate)
Co-polymer - improves mechanical properties

Question 8

What are the constituents of glass ionomer?

Answer 8

acid: polyacrylic acid, tartaric acid
powder: silica 30-40%
alumina 15-30%
calcium fluoride 15-35%
aluminium fluoride 4-20%
sodium fluoride 4-10%
*more silica, more translucent

Question 9

What are the constituents of CaOH?

Answer 9

base: calcium hydroxide 50%, zinc oxide (filler) 10%, zinc stearate (filler) less than 1%, n-ethyl toluene sulphonamide (plasticiser) 40%
catalyst: butylene glycol disalicylate (reactive element) 40%, titanium dioxide 13-14%, calcium sulphate (filler) 30%, calcium tungstate (filler and radiopaquer) 15%