Bonding to Enamel and Dentine

Question 1

What are the 4 main challenges in the oral environment?
What must the materials used in the oral environment be ultimately?

Answer 1

pH
Temperature
Saliva- moisture control
Force- fracture, fatigue, chip

Must be biocompatible- do no harm

Question 2

Label:

Answer 2

Question 3

What are the different types of direct restorations? i.e. inlay

Answer 3

Question 4

Why is it easier to bond to enamel vs dentine?

Answer 4

Because enamel is more homogeneous- 98% inorganic
Whereas dentine has more organic components, and changes composition depending on depth.

Question 5

What are the main direct restorative materials?

Answer 5

Dental Amalgam

Adhesives:
Composite resins
Glass ionomers
Combination adhesives

Question 6

What improves GIC-I adhesion?

Answer 6

Dental conditioner bonding agent, a weak acid (poly acrylic) that removes dentine smear layer

Question 7

What is dentine conditioner used for?

Answer 7

Acid etching=

A weak acid (poly acrylic) that remove the dentine smear layer and condition dentine/enamel before layer of glass ionomer is placed.

What remains is a structure consisting of collagen fibres, the main organic component of dentine

Question 8

Adhesion is defined as?

What characteristics affect adhesion?

Answer 8

The strength that causes unlike materials to adhere (stick) together

Surface tension, Wetting, viscosity, film thickness

Question 9

Why is biomaterial surface important in restorations?

What are the components in biomaterial surface interphase?

Answer 9

These are critical for controlling cell-to-material interactions/adhesion. Biomaterial surface characteristics include: roughness, wettability, surface tension, chemical and electrical composition, and homogeneousness

To maintain:

• Dentine-pulp complex protection- maintain pulp vitality
• Bonding steps: dentine to enamel, biomaterial surface- aim to adhere to different materials
• Restoration- re-establish function and aesthetic

Question 10

What are these products used for?

Answer 10

Question 11

What factors affect the success of composite restorations?

The tooth substrate being adhered to:

Answer 11

• Composition of enamel, dentine, cementum: organic, tubules, permeability, ability to be roughened
• Age changes in enamel: permeability decrease in water content, wear, fluoridation
• Polymerisation shrinkage/c-factor: ratio of bonded: unbound surfaces.
• Over-drying: avoid collagen collapse.
• Depth of cure

Question 12

What are two factors affecting composite cure?

Answer 12

Overdrying

Depth of cure

Question 13

Why do you not over dry?

Answer 13

Collagen fibres can collapse

Question 14

What affects dentine bonding?

How long do you etch dentine compared to enamel?

Answer 14

• Living tissue! (odontoblastic extensions): Etching differs: 15 secs dentine, 30 seconds enamel
• Stresses at resin-dentine interface: polymerisation shrinkage, coefficient of thermal expansion issues

Question 15

What are the three steps in the etch technique of dentine?

Answer 15

1. Etch (15 secs) conditioning - cleans surfaces and dissolves apatite crystals
2. Prime using hydrophilic monomers (acetone)- penetrates collagen network, makes surface hydrophobic
3. Bond (adhesive agent)- low viscous Bis-GMS (forms an interface to the filling composite)

Question 16

Define the smear layer

Answer 16

After preparation with rotating instruments, a smear layer is formed at the dentine surface containing collagen pieces and grinding mud. The thick ness is 1-2um.

Question 17

Describe the hybrid layer

Answer 17

Key to all dentine adhesive materials

Demineralised dentine and exposed collagen network (by etching) infiltrated by polymerised adhesive resin (resin monomers/bonding)

Question 18

What is conditioning?

Answer 18

• Conditioning- removes the smear layer with poly acrylic weak acid, opening the dentine tubules and exposes the collagen

Question 19

What are the basic ingredients of composite resin materials?

Answer 19

• Matrix (continuous phase) 2-4 monomers
• Filler (dispersed phase) (filler particles different shape and size)
• Coupling agent- (internal interface coupling agent)

Question 20

What is a hybrid composite?

Answer 20

Contains micro and macro fillers

Combining two or more types of fibres

Question 21

What are the three types of adhesion?

Answer 21

• Mechanical: needs interlocking
• Specific: through ionic or covalent bonds- GICs, silicates, dental cements
• Effective: combination of both (resin based GICs)

Question 22

What is primer?

Answer 22

Hydrophilic molecule that wets adherents and promotes bonding

Question 23

What are the critical reflection steps needed for success of a restoration?

Answer 23

• Cavity preparation
• Restorative material selection
• Etching vs dentine/pulpal protection

Question 24

Differentiate the etch and rinse adhesive bond GENERATIONS to the self-etch adhesives:

Answer 24

• Etch and rinse adhesives: 4th (3 step), 5th (2 step)
• Self-etch adhesives: 6th (2 step) and 7th (2 step)

Question 25

What is acid etching?

Answer 25

process of cleaning or roughening the tooth surface with 35% phosphoric acid to increase surface energy

Question 26

What is the dentin smear layer? How is it removed? and Why?

Answer 26

Debris of dentine remaining on the dentine after cavity prep using a rotary instrument It is removed with acid etch to expose collagen matrix and dentine tubules- to create mechanical retention and tags.

Question 27

How does the **etch-rinse approach** vs **self-etch approach** differ in regards to the smear layer AND hybrid layer?

Answer 27

**Etch-rinse approach:** applying phosphoric acid (etch) demineralises and totally removes the smear layer and exposes the collagen matrix and dentine tubules for mechanical retention- therefore hybrid layer consists of the exposed layers and adhesive monomer. **Self-etch approach:** when no etch is applied, rather an acidic primer, it doesn't demineralise the smear layer, which means it partially is incorporated into the hybrid layer.

Question 28

Role of acid-etch and rotary instruments in cavity prep:

Answer 28

Rotary instrumentation creates the smear layer that is a layer of grinding dentin debris. Acid-etching removes this layer and roughens the tooth surface (exposing dentinal tubules) to allow **inter mechanical interlocking with resin.**

Question 29

What are the 5 types of pulp protection?

Answer 29

Chemical, Electrical, thermal, mechanical, pulp medication

Question 30

On dentine “the deeper you go the more permeable the pulp becomes”. What is used to recover injured pulp?

Answer 30

Bases: layer of cement placed beneath the permanent restoration to encourage recovery and protect the pulp.

Question 31

What are the clinical differences between shallow cavities and deeper cavities?

Answer 31

Shallow: just enamel - the highest rate of bonding is around enamel because of the high inorganic content, making it more predictable how it will bond. Deeper: dentine has more changing conditions the deeper the cavity in inorganic/organic content.

Question 32

What does acid etching achieve?

Answer 32

* increases surface energy * Cleans and removes smear layer- Dissolves rods * Creates space for resin tags * Allows a hybrid layer to form between collagen matrix and resin polymer

Question 33

How does the **configuration factor** affect the success of the composite restoration?

Answer 33

The ratio of bonded to unbonded surfaces. Higher the C-factor, higher chance of polymerisation shrinkage, more post-op sensitivity

Question 34

Compare infected to affected dentine:

Answer 34

Infected: superficial, wet, soft mushy, Affected: deeper, dryer, demineralised but not invaded by bacteria