Clinical aspects of adhesion

Question 1

How do we know how much tooth tissue to remove?

Answer 1

• Caries risk of patient
• Quality of tissues remaining (infected or affected)
• The restorative material we are going to use (amalgam needs a bigger cavity)

Question 2

What material options do we have to restore with?

Answer 2

• Composites
• GIC
• Biodentine
• Amalgam

Question 3

Why do we use acid etch?

Answer 3

• Create micro-porosities for resin to infiltrate into
• Removal of smear layer
• To give a high energy surface

Question 4

Why do we want a material that is not putting lateral stress on enamel?

Answer 4

When we cut enamel, the prisms tend to be parallel to the cavity wall.

Therefore, lateral pressure can cause the enamel prisms to be separated easily.

Question 5

How can composites cause tooth cracking?

Answer 5

• They shrink by up to 3%
• This puts pressure on the enamel-composite interface
• Can lead to fracture of enamel

Question 6

What bur can reduce the risk of fracture at the interface?

Answer 6

541 diamond bur

Question 7

What are the 4 types of dba?

Answer 7

Type 1 = 3 bottle adhesive, etch prime and bond separately

Type 2 = etching and then primer&bond together as a solvent

Type 3 = etch&primer and then bond (bond seals surface)

Type 4 = all 3 mixed together e.g. Scotchbond

Question 8

Why do we not want to excessively dry the collagen after adding etching?

Answer 8

This leads to the collapse of the collagen network to form an impenetrable mass.
This means the primer will not penetrate into the dentine.

Question 9

Why do we use a rubber dam?

Answer 9

To prevent contamination, prevent inhalation of any equipment, moisture control.

Question 10

How long do we etch, wash and dry for?

Answer 10

Etch: 20s enamel, 10s dentine
Wash: 10s
Dry: 10s

Question 11

Why should we not touch resins when placing them?

Answer 11

• Gloves dont protect operator
• Less contamination of the resin
• Better cross infection control

Question 12

What is the difference that occurs in the smear layer with type 1&2 DBA compared to type 3&4 DBA?

Answer 12

1&2 = removes smear layer

3&4 = dissolves smear layer

Question 13

What does the hybrid layer form between?

Answer 13

Between the dentine collagen tubules and the primer.

Question 14

Type 4 systems are more simple.

What is the main problem?

Answer 14

Breakdown in the bond showing blistering due to water in the adhesive interface.

Question 15

What bifunctional monomer is found in Scothbond?

Answer 15

MDP monomer

Question 16

Where are resin tags forming?

Answer 16

Between dentinal tubules and bond

Question 17

Where does the oxygen inhibition layer form?

Answer 17

Between the bond and the overlying composite.

Question 18

Why does the adhesive layer degrade over time?

Answer 18

• The MMPs are secreted by bacteria which break down the collagen interface and hence the hybrid layer

Question 19

How can we measure the bond strength in the hybrid layer?

Answer 19

Take a tooth, sectioning it and removing the crown.
Flat surface of the tooth is conditioned, etched and primed.

Composite crown is built up on the tooth surface.

Surface is then left 24h in distilled water and a slow speed diamond saw is used to section the tooth into slabs.

The tooth is sectioned again at 90 degrees to make matchstick shapes.

The matchsticks are attached a device and pulled apart to measure the bond strength in the small area.

Question 20

How do we perform atraumatic restorative treatment?

Answer 20

• Remove the reservoir of bacteria to provide a cleansable tooth surface
• Transitional restorations

Question 21

What type of bonding does GIC have?

Answer 21

Chemical bonding between carboxyl ions in GIC and calcium phosphate in enamel and dentine.

Question 22

What is the reaction with biodentine?

What does the water contain and why?

Answer 22

Tricalcium silicate + water to make calcium silicate hydrate and calcium hydroxide.

Water contains calcium chloride which accelerates the reaction.

Question 23

Why is high pH stimulate in biodentine?

Answer 23

Stimulates the laying down of reparative dentine (formed by pre-odontoblast cells after lots of trauma).