Dr. lama khaled El Banna Faculty of Oral and Dental Medicine Al – Azhar University operative dentistry part two

2. College of Dentistry
Operative Dentistry II
Introduction to Adhesive Dentistry -3-
Dr. Hazem El Ajrami

3. 2. Self-etch adhesives (Smear layer dissolving
adhesives):
Self-etch adhesives do not comprise a
separate etching or rinsing step. They use
acidic primers, called self-etching primers,
which simultaneously condition and prime
the tooth substrate. As a result, the dissolved
smear layer and the demineralization
products are not rinsed away but
incorporated in the adhesive resin and into
the hybrid layer.

6. • The morphological feature of the hybrid layer
produced by self-etch adhesives depends on
their aggressiveness or acidity. The more
aggressive the adhesive, the deeper is the
hybridization. Mild self-etch adhesives perform
shallow demineralization of dentin producing
shallow or thin hybrid layer and the smear plugs
are not completely removed. In addition,
hydroxyapatite crystals are available around the
collagen fibrils as a result of mild
demineralization.

7. Interaction of different self-etch adhesives with
dentin

8. • Strong or aggressive self-etch adhesives
produce a thick hybrid layer with long resin
tags resembling etch-and-rinse adhesives.
Intermediary strong self-etch adhesives lie
between mild and strong adhesives.

9. • Two-step self-etch adhesives consist of a
hydrophilic aqueous acidic primer solution and a
separate hydrophobic adhesive resin. A
commercial example for mild two-step self-etch
adhesive is Clearfil SE (Kurary). Despite the
shallow hybridization of mild self-etch
adhesives, they can reach satisfactory bond
strength values. Some mild self-etch adhesives
comprise monomers that are capable of chemical
interaction with hydroxyapatite crystals, e.g. 10-
MDP monomer in Clearfil SE.

11. • A commercial example for two-step
intermediary strong self-etch adhesive is
AdheSE (Ivoclar Vivadent).
• One-step self-etch adhesives are complex
mixtures of both hydrophillic and hydrophobic
monomers. An example for strong one-step
self-etch adhesive is the single-packaged unit
dose Prompt L-pop (3M ESPE).

14. • Advantages of self-etch adhesives:
1. Simplification of the clinical application
procedure by reducing application steps and
omission of post-etching rinsing phase. It has
a time-saving application procedure.
2. Simultaneous demineralization and resin
infiltration, overcoming the problem of over-
etching or incomplete resin impregnation.

15. 3. Does not increase permeability of dentin, thus
reducing the potential post-operative
sensitivity.
4. Technique sensitivity resulting from dentin
wetness is prevented. Thus, the problem of
dryness (collapse of collagen) and over-
wetting is eliminated.
5. Possibility for particle-filled (shock-absorber)
adhesive.

16. • Disadvantages of self-etch adhesives:
1. Insufficient long-term clinical results. The
incorporation of the smear layer into the
hybrid layer could complicate the bond
durability.
2. One-step self-etch adhesives have relatively
low bond strength.
3. Adhesion potential of mild self-etch adhesives
to enamel is weak, because of their mild
aggressiveness which results in improper
enamel etching. Thus, separate pre-etching of
enamel with phosphoric acid might be
recommended before application of the mild
self-etch to enamel and dentin.

17. 3. Glass ionomer adhesives (smear layer
modifying adhesives):
The third adhesive approach is based on the
technology of glass ionomer and its self-
adhesive capacity. These adhesives are resin-
diluted versions of resin-modified glass
ionomer. Example for glass ionomer adhesive
is Fuji Bond LC (GC Corporation).

19. • Conditioning dentin with weak concentration
(10-20%) polyalkenoic (polyacrylic) acid for
about 10 seconds removes the smear layer but
not the smear plugs. It thus provides a clean
dentin surface with shallow demineralization for
hybridization and sufficient residual
hydroxyapatite for chemical bonding. The acid
is then rinsed with water and the resin-modified
glass ionomer bond is placed.

20. • Thus, their bonding mechanism is twofold;
chemical adhesion between calcium in
hydroxyapatite and carboxylic group of
polyalkenoic acid and limited demineralization
of enamel and dentin with subsequent
infiltration and micromechanical interlocking
(shallow hybridization).

21. • Advantages of glass ionomer adhesives:
1) Fast and simple application procedure.
2) Twofold bonding mechanism.
3) Cariostatic potential by release of
fluorides.
4) Viscous particle-filled adhesive that act as
a shock absorber.

22. • Disadvantages of glass ionomer adhesives:
1. No long term clinical data.
2. Adequate adhesion to enamel requires total
smear layer removal.

23. Thank You