Principles of Adhesion, Acid Etch and Dentine Bonding Agents including self etch

Question 1

what does adhesive materials offer potential to?

Answer 1

• Seal vulnerable pits and fissures
• Conserve tooth tissue
• Reduce/eliminate microleakage

Question 2

what are the 3 approaches to achieving adhesion?

Answer 2

-Micromechanical attachments
E.g. acid etch and application of resins

-Chemical adhesion to enamel/dentine
E.g. coupling agents/cements containing polyacids (not considered further in this lecture)

-Complex – involving wetting, penetration and formation of bound material of restorative substrate interface
E.g. modern dentine bonding agents

Question 3

what helps achieving adhesion?

Answer 3

if the agents concerned demonstrate wetting (contact angle)

- lower the angle, the better wetting

Question 4

why does good wetting help adhesion?

Answer 4

Attraction between adhesive and adherend lowers surface tension of adhesive so will flow into irregularities

Question 5

what is the purpose of acid etch? (enamel)

Answer 5

Increases surface roughness microscopically

Increases enamel surface energy:

• removes surface contaminants
• increases wetting
• facilitates micromechanical retention

Question 6

what factors affect adhesion?

Answer 6

• Etching time
• Washing
• Drying

Question 7

Describe how etching time affects.

Answer 7

• Enough for effect
• Not to long as allows re precipitation of Calcium and Phosphate
• Typically 10-60 seconds

Question 8

Describe how washing affects.

Answer 8

Approx 60s to remove debris

Question 9

Describe how drying affects.

Answer 9

To enable hydrophobic resin to penetrate and attach

Question 10

With adhesion to dentine , why is it important to stick to same manufacturer?

Answer 10

• to avoid potential chemical compatibility problems (composite and DBA)
• to avoid light curing problems especially if using LED (composite, DBA and curing unit)

Question 11

What are the properties of an ideal dental adhesive?

Answer 11

• a high bond strength to enamel & dentine
• an immediate and durable bond
• a reliable bond
• prevent bacterial ingress
• be safe to use
• be simple to use

Question 12

What are properties of dentine?

Answer 12

• hydrophilic (adhesives are hydrophobic)
• a vital tissue
• consists of inorganic & organic material
• is covered by a smear layer

Question 13

What are problems with dentine bonding?

Answer 13

• Cavity preparation results in a smear layer that occludes tubules
• Dentinal tubules following removal of smear layer but no air drying

Question 14

what is the manufacturer term for primer?

Answer 14

dentine conditioner

Question 15

what is the manufacturer term for coupling agents?

Answer 15

Primers

Question 16

what is the manufacturer name for sealer?

Answer 16

sealers

Question 17

Describe primers.

Answer 17

• acids

- alter surface appearance and characteristics of dentine

Question 18

Describe coupling agents.

Answer 18

components that do the sticking

Question 19

Describe sealer.

Answer 19

• flows into dentinal tubules
• seals dentine with surface layer rich in methacrylates
• ensures bonding to the resin in the composite

Question 20

Give example of dentine conditioners and describe how they work.

Answer 20

• Eg. Maleic, oxalic, phosphoric, nitric acids
• Acid base reaction with hydroxyapatite
• open dentinal tubules
• demineralize surface dentine to a depth of 4 microns

Question 21

Describe how coupling agents (primers) work.

Answer 21

• Act as adhesives
• Bond hydrophobic composites to hydrophilic dentine
• General formula M-R-X dissolved in volatile solvent

Question 22

what is the most popular coupling agent (primer)?

Answer 22

HEMA

Question 23

Describe the effects of HEMA.

Answer 23

• Dermatological effects and rubber gloves
• Bonds to hydroxyl of the apatite and amino groups of the collagen
• Solvent (e.g. ethanol/acetone) enhances penetration by seeking and displacing water carrying the coupling agent with it

Question 24

Describe sealers.

Answer 24

• Resins

- mix of BIS-GMA & HEMA

Question 25

Discuss the time depended degeneration.

Answer 25

• Acid opening of tubules risks nano leakage
• Dentine etch greater than resin can penetrate
• Dentine microstructure disruption and failure

Question 26

what are the main 3 stages?

Answer 26

1. Application of etchant, washed off creating demineralised dentine layer
2. Application of the primer
3. Application of the sealer

Question 27

what are the two stages of approach one?

Answer 27

1. Application of etchant, washed off creating demineralised dentine layer
2. Application of the primer and sealer in single solution

Question 28

what are the two stages of approach two?

Answer 28

1. Application of self etching primer

2. Application of the sealer in single solution

Question 29

what is the single stage?

Answer 29

1. Self etching primer and sealer applied as a single solution
   (Components supplied in two pouches that are mixed before application
   Number of clinical steps are now 4:
   1 -dispensing and/or mixing the two components
   2- application to the enamel and dentine surface
   3- drying
   4- light curing)