DLA 1201, Exam 5

1. Principals of Bonding
CHAPTER 5

2. Basic Principles of Bonding
 In dentistry, the term bond, or bonding, is used to describe
the process of attaching restorative materials to the tooth by
adhesion.
 When describing cosmetic restorations, such as porcelain or
composite veneers, patients often use the term bonding.
 The basic principles of the bonding process involve preparing
the surface of the tooth or restoration.

3. Basic Principles of Bonding
 Preparing the tooth surface includes removing decay, plaque,
and debris.
 The tooth then is etched or conditioned with a 10% to 42%
solution of phosphoric acid.
 This conditioning removes microns of tooth to provide a
rough surface to which bonding can occur.
 https://www.youtube.com/watch?feature=player_detailpage
&v=IHoBkQtVdeo

4. Bonding to an etched surface:
When a resin bonding agent or primer is flowed over
the etched surface, it penetrates into the microscopic
pores.
When a resin bonding agent cures, it forms resin tags
that adhere to the etched surface of the tooth.
The resin bonding agent then will chemically bond to
other resins placed over it, such as composite resin.

5. Primary and secondary bonds:
The primary or chemical bond occurs through
adhesion when the bonding agent and the
composite resin material adhere to each other.
The chemical bond is stronger than a secondary or
physical bond.
An example is adhesion of paint to a metal surface.

6. Surface wetting:
Etching increases the ability of the bonding
material to wet the tooth surface by creating a
high surface energy.
Good wetting increases the contact of the
material and the tooth; poor wetting prevents
complete contact.
For this reason, bonding agents are typically
made of a low-viscosity material.

7. Bond strength:
The strength of the bond is determined by the
amount of force needed to break the two
materials apart.
This is accomplished by pulling the two materials
apart or by applying force until the bond fails.
An enamel bond is typically stronger than a
dentinal bond.

8. Enamel Etching
Removes a small portion of the surface
Removes the smear layer
Etching times
Suggested times for
Permanent teeth
20-30 seconds
Highly mineralized teeth
Up to 60 seconds
Primary
60 seconds or more
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9. Enamel Etching
 The small surface of the enamel that is removed with etching
reduces the enamel rods and opens porosities among the
rods.
 The removal of the smear layer also occurs during etching, and
the smear layer is made up of debris on the enamel or
dentinal surface that results from the cutting of tooth structure
during the cavity preparation.
 The smear layer comprises bacteria, salivary components, and
tooth dust.

10. Enamel Etching
 Clinical trials show good results in some teeth in as short as 10 seconds
of etching.
 For permanent teeth, the etch time is usually 20 to 30 seconds.
 Highly mineralized teeth may be more resistant to etching and may
require up to 60 seconds of etching.
 Primary teeth should be etched for longer periods (60 seconds or
more), because the enamel has a prism pattern that is not well
structured.
 Etching should take approximately 20 to 60 seconds, depending on the
manufacturer’s instructions and the type of procedure to be completed.

11. Enamel Etching
 The etched surface should have a
frosty appearance when dried.
 When a cavity preparation involves the
etching of both enamel and dentin
and the preparation is left slightly
moist for wet denting bonding, the
frosty appearance of the enamel
cannot be determined.

12. Enamel Etching
 The acid etchant comes as a liquid and a gel.
 The application of the etchant depends on the form that is
being used.
 The recommended rinsing times for acid gels is approximately
10 seconds or longer. (we say 20-30 seconds)
 Rinsing times shorter than 5 seconds may not remove residual
silica.
 Rinsing times for liquid etchants can be shorter – 5 to 10
seconds.

13. Dentin Etching
Smear layer
Acidic primers
Phosphoric acid etching
Moist dentin for bonding
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14. Dentin Etching
The dentin has a higher water content because of its
organic makeup.
It also contains collagen and other fluids from the pulp
chamber.
The smear layer, which is made up of debris on the
enamel or dentinal surface resulting from the cutting
of tooth structure during cavity preparation, must be
removed before the bonding procedure is performed.

15. Smear layer
The smear layer contains plaque, bacteria, pellicle,
salivary components, blood, and tooth dust.
The smear layer sticks tenaciously to the surface, plugs
the openings of the dentinal tubules, and cannot be
washed off with use of air-water spray.

16. Dentin Etching
Bonding agents that use acidic primers to etch
the enamel and dentin penetrate the smear layer
and incorporate it into the bonding agent, since
there is no rinsing used with these systems.
https://www.youtube.com/watch?feature=player_
detailpage&v=TMiN029CWLU

17. Dentin Etching
Etching dentin with phosphoric acid dissolves the
smear layer first, and then portions of the
hydroxyapatite crystals from the surface of the dentin,
creating a porous surface and exposing the meshwork
of collagen fibrils that are part of the dentin matrix.
This opens the dentinal tubules, which leaves a rough,
porous surface.

18. Dentin Etching
Dentin has a lower mineral
content and needs to be etched for
only about 10 seconds.
Over-etching leaves a weaker
bond.

19. Dentin Etching
Wet dentin for bonding is where the acid is removed
by rinsing for at least 10 seconds.
The excess water is removed by a gentle stream of air,
but the dentin surface must be moist to keep the
collagen fibrils fluffed up.
https://www.youtube.com/watch?feature=player_detai
lpage&v=EZr8Tpy3GtM

20. Enamel Bonding
Enamel bonding
resins
Single component
Resin tags
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21. Enamel Bonding
Bonding agents are low-viscosity
resins dissolved in solvents, typically
acetone or ethyl alcohol, that
penetrate porosities in the tooth
surface created by etching.

22. Enamel Bonding
Bonding agents for enamel
requires only a single
component – low-viscosity
liquid.

23. Enamel Bonding
 When the resin is cured by a chemical process or by light-
activation, it locks into the microscopic spaces and
irregularities, producing resin tags.
 The resin tags secure the resin to the enamel and create a very
strong bond.
 Contaminates on the surface, such as saliva or blood, can
dramatically lower the strength of the bond to the enamel.
 This is the major reason why good isolation is so important.

24. Dentin Bonding
Dentin bonding resins
Resin primer
Solvents
Adhesive resin
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25. Dentin Bonding
Bonding agents for dentin are viewed as two
types:
(1) the resin primer that penetrates etched dentin
and enamel and lays down a resin layer and
(2) adhesive resin (bond) that is applied over the
primer.
The two resins chemically bond to each other.

26. Dentin Bonding
The initial resin prepares or "primes" the
tooth surface (hence why we call it
“prime/primer”), and the second resin
chemically bonds to the primer.
The primer is placed first and is dried, to
remove the solvent and the remaining water.

27. Dentin Bonding
The first step of bonding to dentin requires
the primer to penetrate water on the surface
of the tooth.
In order for the resin to penetrate through
the water, it must be dissolved in a solvent
that can penetrate water and carry the resin
with it.

28. Dentin Bonding Resins
 The primer is composed of hydrophilic (water-tolerating) monomers
and molecules that allow it to penetrate water.
 Usually HEMA (2-Hydroxyethyl methylacrylate)
 The bonding agent is applied over the primer.
 This is usually bis-GMA, TEGDMA, and urethane dimethacrylate
 The initial resin prepares (or primes) the tooth, and the second
chemically bonds to the primer.
 Some manufacturers have combined the primer and bonding resin into one
bottle to eliminate one step in the process.

29. Wet Dentin Bonding
 Bonding to moist dentin was the first technique to achieve
good bond strengths in dentin.
 The dentin is kept moist to keep the collagen fibrils from
collapsing into a thick mat that blocks penetration of the
bonding agents.
 A primer is more important to dentin bonding than enamel
because the primer contains hydrophilic groups that penetrate
wet, etched dentin and keep the meshwork of collagen fibrils
expanded, so that the adhesive resin can penetrate

30. Solvents
For the resin to penetrate through the water, it must be
dissolved in a solvent that can penetrate water and
carry resin with it
The solvents allow the resin to penetrate water on the
dentin an din dentin tubules, and to penetrate around
collagen fibrils and into porosities in the tooth surfaces
created by etching

31. Solvents
 Solvents are usually acetone, ethanol (ethyl alcohol), or a combination of
ethanol and water
 In general, the solvent is the largest portion of the bonding agent, making up
60% or more of the material
 Acetone is a highly volatile solvent
 Its rapid evaporation may require that two or more coats of the bonding resin be applied to
ensure adequate sealing of the dentin.
 Ethanol evaporates more slowly, so it may need a longer drying time.
 All bottles must be recapped immediately after dispensing, to prevent
evaporation of the solvent, which leads to gradual thickening of the resin with
less ability to penetrate etched dentin.