Enamel and resin

Question 1

What does acid etching do

Answer 1

It converts a low enamel smooth surface into a high energy irregular surface. Due to the enamel grooves, the material can be interlocked when polymerisation occurs.

It removes surface contaminants and increases wetting- which allows the adhesive to flow into the irregularities.

It removes the smear layer ( in a cavity prep/trauma, dentinal tubules usually release dentinal fluid and this forms a smear layer. Acid etch removes this

Etched dentine exposes the layers of collagen and widens the dentinal tubules

Question 2

Why is it difficult to bond to dentine

Answer 2

1) more organic matrix than enamel
2) enamel rods are parallel whereas collagen is mixed
3) smear layer decreases pentratibility

Question 3

What are primers

Answer 3

These are like dentine conditioners- they alter the surface appearance and characteristics of dentine- it forms an acid- base reaction with hydroxyapatite and opens dentinal tubules

MRX- M is a methylcrylate group that bonds to resin
R- spacer molecule that waggles
X- bonds to dentine

Question 4

What is the difference between primers and etch

Answer 4

Primer- open dentinal tubules

Etch- infiltrates the tooth surface

Question 5

What is the most popular primer

Answer 5

HEMA- binds to hydroxyl of apatite and amino groups of collagen

Question 6

What are the sealers

Answer 6

They bind the primers to the overlying composite resin. They are a mix of bis GMA and HEMA

Question 7

3 stage presentation

Answer 7

1) application of etchant, washed off creating demineralised dentine layer.
2) application of primer
3) application of sealer

Question 8

2 stage presentation

Answer 8

1) Application of etchant, washed off creating demineralised dentine layer
2) application of primer and sealer in a single solution

OR

1) application of a self etching primer
2) application of a sealer

Question 9

one stage presentation

Answer 9

Application of a self etching primer and sealer