Modified Heat-cured Acrylics

1. Microwavable acrylic2. Rapid-cured acrylic3. High impact strength acrylic4. Fiber-reinforced acrylic

Rapid-cured acrylic

An altered initiator that allows denture base processing in boiling water for only 20 min.

Advantages Rapid curing with minimal porosity

Disadvantages High % of residual monomer (3-7 times > Conv. HCA)

Lower mechanical properties Porosity of bases 6mm thick

High impact acrylic

Powder is a graft copolymer of PMMA - butadiene rubber

2 formats of polymer beads are exist

No cross-linking is added to the composition

Is better than

Because it produces better dough characteristics

Rubber

Acrylic

Rubber

Acrylic

Advantages High impact strength Low crazing rates Low residual monomer contents Good attachment to art. Teeth and good fit

Disadvantages Expensive Reduced stiffness

High impact acrylic

Fiber and metal- reinforced acrylic

Certain fibers (Carbon, glass, Kevlar, Polyethylene) and metal fillers (Zerconia and alumina) are incorporated in acrylic powder

Drawbacks Carbon fibers cause black discoloration Glass fibers are irritating and could injure soft tissues Kevlar fibers complicate the packing process and gives

straw color Polyethylene fibers is promising Adding metal fillers poly. Shrinkage but deteriorates

the properties

Chemically-cured Acrylics

A chemical compound ( 3ry amine Activator) is added to the monomer

composition to activate the initiator

An activator paste (P-toluine sulphonic acid) could be added to the regular acrylic

to activate the polymerization at room temperature

Characters of the chemically-cured acrylic

Polymer beads have lower mol. wt. Liquid contains chemical activator (3ry amine) to start

the polymerization at room temp.

The material provides; 1. lower degree of polymerization

2. Lower mechanical properties

3. Higher % of residual monomer

4. Higher rate of porosity

5. Higher rate of water sorption

6. Lower color stability

7. No thermal shrinkage

8. Oversized dentures (+ 0.3-0.4%)

Characters of the chemically-cured acrylic

Practicability

1. Short processing time (10-15 min)

2. Complete polymerization occurs at room temp in 3 hrs

3. Both compression molding or fluid resin techniques could be used to fabricate denture bases

Applications:- Denture base (temp &permanent)- Repair of broken dentures- Special trays

Fluid resin technique

Light- cured Acrylics

The BVL is used to activate the photo-sensitive initiator named

Comphroquinon

The material is a composite structure

Usually present as sheets or robs in light-proof pouches

Characters of the light-cured acrylic

Composition: Composite Paste made of Matrix of UDMA and PMMA Microfine silica fillers Organic fillers (Prepolymerized polymer beads) Photoinitiator

The material provides;

1. No MMA monomer is present (no allergy)

2. Lower physical and mechanical properties

3. Lower rate of polymerization shrinkage

4. Better fit

Applications Denture base Repair of broken prostheses Special trays

Denture construction No flasking is required Adaptation of sheet material over the cast to

form the denture base light curing for 5 min Artificial teeth are then seat over the rob material

light curing for another 5 min

Characters of the light-cured acrylic