Resin based restorations - Composite

Question 1

Resin based restorative materials and fissure sealants

Answer 1

Dental composites, Glass polyalkenoate cements (GIC) & Fissure sealant

Question 2

What is a Filling material?

Answer 2

Material that replaces missing tooth, generally an undercut cavity cut in the removal of caries.

Initially fluid (paste) then sets solid.

Prevents further caries.

Restores tooth function

Question 3

What do we want a filling material to be?

Answer 3

Match properties of natural tooth
- hardness
- modulus (stiffness)
- expansion (cold liquid may cause shrinkage, filling may fall out)
- tooth coloured
- non toxic

Sufficient working time

Setting time

Question 4

What is a composite?

Answer 4

Material with two or more distinct phases

• matrix
• interface
• filler

Question 5

What is dental composite?

Answer 5

• Resin
• Silane coupling agent (helps glass stick to resin)
• Glass

Question 6

Dental composite

Answer 6

Resin
Combination of monomers, which form the matrix via addition polymerisation.
– BIS-GMA (bisphenol glycidyl methacrylate)
– Others such as UDMA (urethane dimethacrylate)

Filler
– Glass
– Other materials

Question 7

Filler in dental composite

Answer 7

Chemical (bonding agent)

Mechanical
- (glass - stiff, hard, strong) unlike resin so this makes it better suited for oral environment
- Abrasion resistance

Optical
- Absorption of water, coffee, tea etc causing staining

Handling
- Changed by changing filler / amount of filler (conventional, micro filled or hybrid filler)
- change in size of filler particles - affect translucency, colour etc

Question 8

Other requirements when using dental composite?

Answer 8

Bonding agent
- hydrophobic composite does not bond to wet surface
- bonding agent

Removes smear layer so tubules are no longer blocked

Question 9

Glass polyalkenoatecements or glass ionomer cements (GIC)

Components?

Answer 9

• Polymer
• Silica gel (coating around the glass occurs during setting process)
• Ionomer glass filler

Question 10

GPAC or GIC

Answer 10

Resin–
Polyacid
- Polyacrylic acid
- Polymaleic acid

Filler
- Fluoro-alumino-phospho-silicate glass
- reactive glass unlike inert glass in dental composite

Question 11

Setting reaction

Answer 11

acid + base —> salt + water

poly acid + base —> poly salt + water

Ions from glass - Ca, Al, F-
O2 and H20

Question 12

How does GIC bond?

Answer 12

GIC bonds directly to the tooth structure

Don’t have to worry about moisture control
GIC can bond to a damp tooth

Question 13

GPAC / GIC

Answer 13

Chemical - filler reacts and allows reaction to occur

Mechanical - glass affecting properties

Optical - similar coloured tooth but translucency not good (good for posterior not anterior)

Handling - sticky material

Question 14

Evaluate

• composite
• glass polyalkenoate
• polyacid modified resins
• resin modified GPA

Answer 14

Question 15

Polyacid Modified Composites

Answer 15

UDMA (urethane dimethacrylate).

Fluorosilicate glass.

Modified resin has acid groups which slowly react with theglass when in contact with water.
– Low Fluoride release.
– Needs bonding agent

Question 16

Resin Modified GPAC / GIC

Answer 16

HEMA (Hydroxy ethyl methacrylate), which can be light activated, is added to the polyacid.
– HEMA can cause and allergic reaction handle with care

GIC Modified with HEMA (allergy caution)
Sets with blue light
- acid base reaction occurs over few weeks

Question 17

Fissure sealants

Answer 17

Unfilled resins
Paint onto fissures to seal them
Prevents caries
Lasts a few years