Materials Quiz 6

Requirements of Dental Cements

film thickness, long working time, good aqueous and acid resistance, high compression and tensile strength, cariostatic effect, translucency and radiopacity

two liners used for direct and indirect pulp caps

Indirect- Ca(OH)2
Direct - MTA (Mineral trioxide aggregate)

Purpose of cement/luting agent

Fill space or bind adjacent objects

Zinc phosphate powder consists of

90 % zinc oxide (primary reacting)
8.2 % magnesium oxide (improves working characteristics)

Zinc phosphate liquid consists of

38.2 % Orthophosphoric acid (free) - primary reacting agent
36 % water - dilutes controls setting time

Reacting to create zinc phosphate (gold standard for luting agents)

Zinc oxide + phosphoric acid

Factors controlling the rate of set

Powder composition - powder/liquid ratio
Degree of powder calcination - Incorporation rate
Particle size of powder - Mixing temperature
Buffering of liquid - manner of spatulation
Water content of liquid - water contamination or loss from liquid

mixing time for zinc phosphate, what happens to pH when setting

2 min (15s + 15 + 15 + 20 +20 +35s) / increases

Advantages and disadvantages of zinc phosphate

Adv: Mixed easily w/ slow addition of powder, set sharply due to moisture, adequate strength
Dis: Pulp irritation, lack of antibacterial action, brittleness, lack of adhesion

ZOE powder composition

ZnO + polymeric resin
Zinc oxide - 69% (primary)
White rosin - 29.3 % (decreases brittleness)

ZOE liquid composition

Eugenol - 85% (obtunds pain)

olive oil - 15% (plasticizer)

ZOE properties

Antiseptic, good marginal seal, low compressive strength, adheres to metallic instruments

ZOE adv and disadv

Adv: ease of use, antibacterial, anodyne effect on pulp, good sealing
Dis: Low strength/abrasion resistance, high solubility, little anticariogenic action, odor

What is glass ionomer

Glass powder (Fluoroalumino Silicate Glass)
Ionomer (Ionic Polymer) )polycarboxylate acid)
Water

Glass ionomer properties

Compatible with pulp, easy to manipulate, low solubility when set, no metal instruments

Glass ionomer biological advantages

Favorable pulp response

Leaching of fluoride with cariostatic effects

Antibacterial action to low initial pH and ion leaching

Adhesive characteristics

Glass ionomer disadvantages

Slow setting, moisture sensitive, variable adhesion characteristics, radiolucency

Luting vs bonding

Luting - zirconia, cement, tooth
Bonding - Ceramic, primer, cement, adhesive, tooth

Resin based cements

cementation of inlays, crowns and appliances
Direct bonding of orthodontic bands

Resin based cements properties

Short working time, high film thickness, difficult to remove excess, pulp irritation, high comp/tensile strength, insoluble

Type of cements for their respective restorations

Relyx Luting plus = metal-based restorations

Relyx Ultimate = silica-based or glass-ceramic restorations

Relyx Unicem 2 = non-silica-based or zirconia restorations

difference between the two liquid components

Phosphoric acid is inorganic, polyacrylic acid is organic