Adhesives

Question 1

two primary methods used to measure bond strength

Answer 1

SBS

MBS

Question 2

primary method of clinical testing for a dentin bonding

Answer 2

clinical evaluation in non-retentive, Class V , non-carious lesions

Question 3

interaction of negatively charged phosphate or carboxylic acid groups is

Answer 3

chemical (ionic) adhesion.

Question 4

Increasing the surface energy

Answer 4

improves adhesion

Question 5

Roughening or etching a surface

Answer 5

• increases the surface’s surface energy

- creates micromechanical bonding

Question 6

Removing surface contamination

Answer 6

improves surface adhesion.

Question 7

Advantages of adhesion to tooth structure

Answer 7

1) conservation of tooth structure;
2) reduction of marginal leakage;
3) improved restoration retention;
4) makes possible esthetic restorations

Question 8

Types of adhesion

Answer 8

1) mechanical;
2) chemical;
3) diffusional;
4) diffusive

Question 9

Nature of enamel bonding

Answer 9

1) more homogeneous, regular structure; 2) high inorganic content; 3) higher surface energy - especially after acid etching; 4) surface rigidity and stability of bond strength over time.

Question 10

Etching of enamel by acids:

Answer 10

Enamel can be etched to varying degrees by various acids (phosphoric acid, maleic acid, polyacrylic acid, etc.) and varying concentrations of those acids.

Question 11

Etching of enamel by phosphoric acid was discovered

Answer 11

by Buonocore-1955.

Question 12

Phosphoric acid gels ranging from____________ have been used to etch enamel.

Answer 12

10 - 50%

Question 13

Preferred concentration of phosphoric acid for enamel etching is

Answer 13

35 - 40 %.

Question 14

Preferred enamel etching time is minimum of

Answer 14

15 seconds if enamel minimum and dentin max

30 - 60 seconds (enamel only - not dentin).

Question 15

Phosphoric acid is provided both in

Answer 15

liquid and gel form

Question 16

Gel form of phosphoric acid is made of

Answer 16

Fumed silica (inorganic) or polymer thickening agents are used for phosphoric acid gels (~37% Phosphoric Acid).

Question 17

Effects of phosphoric acid etching on enamel

Answer 17

1) creates micropores 5 – 50 microns deep; 2) increases surface energy; 3) increases wettability of the enamel surface.

Question 18

Contamination on enamel:

Answer 18

saliva and enamel “pellicle” (surface layer of salivary proteins which forms rapidly).

Question 19

Cleaning of both enamel and dentin involves use of

Answer 19

non-fluoridated pumise and a rubber cup in a low speed handpiece, following by thorough water rising and air drying.

Question 20

Cleaning the surface increases

Answer 20

surface energy and decreases contact angle on the surface

Question 21

Enamel bonding, after acid-etching, rinsing, and drying; involves the application of

Answer 21

unfilled resin bonding agent composed of low viscosity monomers (Bis-GMA. UDMA, TEGDMA,HEMA), and polymerization agents (initiators, accelerators, stabilizers).

Question 22

Etched enamel shear bong strength

Answer 22

20 MPa

Question 23

steps utilized in enamel bonding:

Answer 23

1- Phosphoric acid etch; 2- Rinse to remove acid + precipitate; 3- Apply hydrophobic bis-GMA monomer; 4- Light cure to polymerize; 5- Add composite resin against air-inhibited bonding agent surface and polymerize.

Question 24

LED stands for

Answer 24

Light Emitting Diode.

Question 25

density and morphology of dentinal tubules changes as dentin depth increases

Answer 25

as depth increases - density of tubules increases and tubule diameter increases

Question 26

Dentin smear layer is produced by

Answer 26

Instrumentation

Question 27

Smear layer composition

Answer 27

cut dentin debris & bacteria

Question 28

Smear layer characteristics

Answer 28

• Reduces dentin permeability ~ 86%
• Weak adhesion to underlying dentin (2-3 MPa
• Thickness (0.5 - 5.0 microns);
• Will not wash off;
• very soluble

Question 29

dentin is a hydrated/hydrophilic substrate, which makes it

Answer 29

difficult to bond to dentin.

Question 30

basic components of contemporary dentin/enamel adhesive

Answer 30

1) AN ADHESIVE MONOMER (Carboxylic Acid or Acid Phosphate Methacrylate)
2) STRUCTURAL, CROSS-LINKING DIMETHACRYLATES – the “structural matrix
3) A SOLVENT, “WATER-CHASING” CARRIER – an ethanol or acetone

Question 31

ethanol or acetone solvent characteristics

Answer 31

• solubilizes the adhesive and dimethacrylates of the adhesive
• reduces the viscosity to improve adhesive wetting, and (3) displaces (i.e. “chases”) water in the dentin

Question 32

role and function of dentin primers as they were introduced in the 3rd and 4th generation adhesive

Answer 32

1) Contain Hydrophilic monomers dissolved in acetone, alcohol, and/or water;
2) Primer solvents (acetone/ethanol) serve to displace water in wet dentin;
3) Primer promotes infiltration into exposed collagen (hybrid zone) after etching;
4) Light air drying drive off solvents/ water ;
5) Primed dentin transforms hydrophilic surface to hydrophobic surface to bond more effectively to final hydrophobic resin adhesive component layer.

Question 33

basic composition of the primer component in two bottle, 4th generation adhesive system

Answer 33

1) Contains a bifunctional monomer that links hydrophilic collagen to hydrophobic resin; 2) Chemical Structure contains: HEMA/Could also contain either: Phophate/Phosphoric acid ester-based monomer and/or Carboxylic Acid -based monomer.

Question 34

Composition of adhesive components

Answer 34

Unfilled or lightly-filled monomers equivalent to enamel bonding Bis-GMA, UDMA, TEGDMA;

Question 35

Function of adhesive components

Answer 35

• Stabilizes the hybrid layer by filling up remaining pores/gaps and creating resin tags in tubules/intertubular dentin
• Links primer to composite resin.

Question 36

What is the hybrid layer

Answer 36

Conditioner (37% Phosphoric Acid/15 seconds max.) demineralizes dentin, removing mineral component and leaving hydrated collagen “sponge” layer;

Question 37

Effect of primer and solvent on hybrid layer

Answer 37

• displaces water in the collagen “hybrid” zone with bifunctional monomers;
• interdiffuse this collagen-rich layer with low-viscosity monomers and resin component

Question 38

Hybrid layer forms from

Answer 38

Polymerization which causes resin component mechanically to interlock with collagen

Question 39

Why keep moisten dentin before bonding

Answer 39

Overdrying collapses the hybrid layer of collagen, preventing penetration of the open collagen matrix to create an adequate hybrid layer.

Question 40

role of solvents

Answer 40

• displace remaining water in collagen (hyrbid zone) and dentin
• carry monomers into collagen
• upon gentle but prolonged air-drying, solvents are removed, leaving monomers behind to polymerized into cured adhesive.

Question 41

Self-etch adhesives, composition:

Answer 41

1) Acidic monomers
2) Structural, crosslinking monomers - both hydrohphilic and hydrophobic;
3) Solvents which include water to lower the pH sufficiently to achieve etching of enamel.

Question 42

Self etch function

Answer 42

1) Simultaneously etch enamel and dentin; 2) Bond to dentin is usually stronger than enamel. 3) Can be used with separate enamel etch of phosphoric acid as first step - but avoid separate dentin etch. 4) Dissolve the smear layer and create a thinner hybrid zone than total etch adhesive systems

Question 43

Clinical efficacy for self etch

Answer 43

• increased staining of enamel margins over time compared to total etch.
• best clinical performance

Question 44

Seventh Generation Self-etch adhesives

Answer 44

• All-in-one” adhesive

- combine conditioner, primer and adhesive in one bottle; one-step - no mixing

Question 45

All in one adhesive characteristics

Answer 45

Low bond strengths; clinical performance thus far is not encouraging.

Question 46

components of a contemporary dentin-enamel adhesiv

Answer 46

1) AN ADHESIVE MONOMER
2) STRUCTURAL, CROSS-LINKING DIMETHACRYLATES
3) A SOLVENT, “WATER-CHASING” CARRIER

Question 47

Light curing initiator: Camphorquinone (CQ) is the

Answer 47

primary viable light initiator also used in dental composite resin restoratives and dental cements.
470nm is peak absorption

Question 48

Light curing accelerator

Answer 48

tertiary amines that transfer free electrons to methacrylate groups and initiate free radical polymerization.

Question 49

Self-cure initiator:

Answer 49

Benzoyl Peroxide (BPO) is the most commonly used chemical-cure initiator.

Question 50

Self-cure co-initiator/accelerator

Answer 50

BPO reacts with certain tertiary amine compounds to form free radicals that cause the polymerization reaction to occur.

Question 51

How do you convert light cured to light and chemical cured

Answer 51

by adding a drop of a second bottle (self-cure activator), which provides a chemical initiator to the first bottle.

Question 52

Issues in dentin bonding:

Answer 52

1) Metalloproteases in dentin (collagen degradation in the hydrid zone); 2) Hydrolysis of the adhesive (water trees); 3) Degradation of the adhesive resin by natural and bacteria esterases; 4) Colonization by bacteria and biofilm formation in marginal gap areas.

Question 53

Methods to avoid issues in dentin bonding

Answer 53

1) Chlorhexidine to inactivate metalloproteases; 2) Gluma (5% glutaraldehyde/35% HEMA/60% Water) to also inactivate metalloproteases and crosslink collagen - prevent degradation.