Week 6 - Dental Adhesives

Question 1

What are reasons for adhesion

Answer 1

• many restorations only possible with adhesion (orthodontic brackets)
• conservation of tooth structure (non adhesive needs mechanical retention)
• reinforcement of weakened tooth structure
• Reduced incidence of post operative sensitivity
• Reduced marginal leakage (marginal seal prevents bacterial invasion)

Question 2

What is the procedure of application of dental adhesives

Answer 2

1. Surface preparation (etching/conditioning)
2. Application of adhesive

Question 3

What is the point of surface preparation (etching/conditioning)

Answer 3

• to remove/modify the smear layer
• to create microporosity on tooth structure which allows resin to seep in and gain retention

Question 4

What is total etch

Answer 4

strong acid which is washed off and removes the smear layer

Question 5

What is conditioning

Answer 5

weak acid which modifies the smear layer and is not washed away

Question 6

What is the function of acid etch for enamel bonding

Answer 6

1. Increase the micro retention by creating an uneven solution of enamel prism
2. Increase the surface tension of enamel by removing surface contamination (e.g. pellicle and smear layer)

Question 7

What are the different types of surfaces which acid etches create

Answer 7

Type 1 core (honeycomb appearance) - prismatic etching
Type 2 periphery (cobblestone like) - prismatic etching
Type 3 is mixed

Question 8

What is the mechanism of bonding for resin/bond

Answer 8

micromechanical

Question 9

is type 1(prismatic) or type 2 (interprismatic) surfaces stronger for bonding

Answer 9

type 1 prismatic

Question 10

Why shouldn’t you over etch enamel

Answer 10

will dissolve the enamel prisms resulting in a smooth surface which make it hard for the resin to adhere to

Question 11

What should you do if there is unsupported surface for incisors

Answer 11

eliminate unsupported enamel and increase the bonding surface by beveling the margins except on the occlusal area

Question 12

What are causes for white lines in composite

Answer 12

1. unsupported enamel cracked due to shrinkage of the composite
2. a thin section of composite cracked under the occlusal force - causing enamel chipping
3. overheating composite when polishing composite without water - composite expands

Question 13

What is the order that products are put on for dentine bonding

Answer 13

1. etch/conditioner
2. coupling agent/primer
3. bond
4. composite

Question 14

what are primers

Answer 14

bifunctional monomers having a hydrophilic end group (OH, COOH, phosphate) a spacer and then a hydrophobic methacrylate end group.

These primers are normally photo initiator/chemically cured.

They also contain a solvent (ethanol, acetone, water) to aid with viscosity and flowability.

Question 15

What are 4th generation bonding systems

Answer 15

Etch and rinse (total etch) + prime + bond

3 bottles

Question 16

what are 5th generation bonding systems

Answer 16

Etch and rinse (total etch) + prime-bond
2 bottles

Question 17

What is 6th generation bonding systems

Answer 17

Self-etching primer (self-etching, no rinse) + bond
2 bottles

Question 18

What are 7th generation bonding systems

Answer 18

Etch-prime-seal (self etching no rinse). One bottle without mixing (MDP-based)

Question 19

what is 8th generation bonding systems

Answer 19

Etch-prime-seal (self etching no rinse). One bottle without mixing, multi modal (MDP + silane + nano fillers)

Question 20

What is MDP

Answer 20

10-Methacryloxydecyl dihydrogen phosphate (MDP)
- phosphoric acid ester monomer
- used in adhesives
- preserves the collagen in dentine by increasing resistance enzymes and inhibiting MMP - increasing longevity of dentine-resin bonding

Question 21

what is MMPs

Answer 21

matrix metalloproteinase
-enzymes naturally present in dentin
- they degrade the collagen fibers in the dentine, disrupting the collagen scaffold which supports the resin adhesive layer
- reduces durability of dentine-resin bonding

Question 22

What type of dentine is the hardest to bond to

Answer 22

carious dentine

Superficial>deep>sclerotic>carious

Question 23

What can cause the break down of dentin bonding

Answer 23

• polymerization shrinkage
• void or porosity due to poor handling
• Different coefficient of thermal expansion
• Internal stress from occlusal load
• Chemical attack, such as hydrolysis

Question 24

what is C factor

Answer 24

he ratio of the bonded to the unbonded surfaces in a dental prep.

Question 25

How is the C-factor related to causing the breakdown of dentin bonding

Answer 25

Shrinkage creates internal stress within the composite which is transmitted tot he tooth structure. The higher the C-factor the greater the stress because there are more bonded surfaces resisting the shrinkage.

This stress can cause debonding, marginal leakage, post operative sensitivity or even fractures in the tooth restoration.

Question 26

What technique do you use to compensate for preparations with high C-factors

Answer 26

incremental layering

Question 27

What is a method of improving the longevity of dentine bonding

Answer 27

Application of chlorhexidine 2% after acid etch and before bond
- it inhibits matrix metalloproteinases (MMPs) preventing degradation of collagen fibres
- apply for 60 sec and then gently air dry