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
Direct Esthetic Tooth-Colored
Restorations -3-
Dr. Hazem El Ajrami

3. 4. Application of liner/base:
Resin composite restorations do not need
pulpal protection except in very deep cavities
where the deepest part is lined with calcium
hydroxide. In moderately deep cavities, the
sandwich technique may be used, where glass
ionomer or resin modified glass ionomer
liner/base is placed under composite. Also a
layer of flowable composite might be used
under packable or highly filled composites to
increase the adaptation and sealing of the first
increment and to act as an elastic layer to
absorb stresses.

5. 5. Matricing and wedging:
The use of well-adapted and well-
contoured smooth matrix strips is essential,
especially with chemically cured composites,
in order to increase its density and obtain
proper contour and marginal adaptation. A
variety of matrices may be used according to
every individual situation. Mylar matrix strip
is commonly used for Class III and IV
restorations.

7. • Wedging is important to stabilize the matrix
and allow for some separation that ensures a
tight contact. The matrix should be placed
before etching and application of adhesive to
prevent them to get in contact with adjacent
tooth. A suitable-sized celluloid crown
former may also be used for Class IV
restorations.

8. Use of Mylar matrix during application of
adhesive system (A) and during packing of
composite (B) in Class IV

10. • For cervical restorations, a Class V clear
matrix may be used. While for posterior
proximal restorations, the choice is either to
use a pre-contoured Mylar matrix with
transparent wedges, or a metallic matrix in a
Tofflemire retainer or in a Sectional matrix
and wooden wedges.

13. • Metallic matrices are better for establishing
proper contact area and fewer overhangs
because resin composites are not as condensable
as amalgam. The Sectional matrix is preferred
over the Tofflemire matrix because its wings
provide proper separation. In addition, wooden
wedges provide better separation than
transparent plastic ones. On the other hand, the
use of transparent matrix and wedges is
advantageous in that composite can be cured
through them, but they might result in flat
contacts and gingival overhangs.

14. 6. Application of adhesive system:
The adhesive system is selected. The
manufacturer's instructions for application of
each adhesive system should be strictly
followed. Usually a longer etching time for
enamel is recommended. To achieve this
clinically, the etchant gel is applied on
enamel first then the cavity is filled with
etchant, which is then thoroughly rinsed in
one step.

16. • If dry bonding technique is followed, the
cavity preparation is dried with short blasts of
intermittent oil-free air until the chalky white
appearance of enamel is observed. In the wet
bonding technique, excess moisture following
rinsing is blotted with a cotton pellet or a
micro sponge until no moisture can be blotted
anymore; dentin should appear shiny and
hydrated.

18. • Primer application time of 15 seconds, as
recommended for most manufacturers, should be
followed to allow monomers to inter-diffuse to
the complete depth of surface demineralization.
With dry bonding technique, this application
time allow for air-dried dentin and collapsed
collagen to re-expand using water-based primer.
While with wet bonding technique, this time
allow for displacement of all surface moisture by
solvent-based primer. Gentle air drying is then
done to evaporate the solvent. If the primer is
placed as a separate step, it is not light-cured.

19. • On the other hand, spreading of the adhesive
layer should be done with brush-thinning
rather than air-thinning to provide sufficiently
thick layer of adhesive to act as an elastic
intermediary joint. This elastic bonding
concept not only counteracts polymerization
shrinkage stresses of resin composite but also
aids in absorbing masticatory forces, tooth
flexure and thermal changes, thus minimizing
the possibility of failure of the bond.

20. • If viscosity of the adhesive is low,
manufacturers often recommend application of
a double layer of adhesive. Filled adhesives
also act shock absorbers and increase the bond
strength of the adhesive. As discussed before
an intermediary layer of flowable composite,
glass ionomer or resin modified glass ionomer
serves the same concept.

21. • In addition, the adhesive layer should always
be cured before application of resin composite.
In this way, the adhesive will not be displaced
when composite is applied and adequate light
intensity is provided to sufficiently cure the
adhesive resin layer.

22. • Because oxygen inhibits polymerization, the
top 15 microns of the adhesive resin will not
polymerize, thus providing sufficient chemical
copolymerization with the resin composite.
This oxygen-inhibited layer is also important
in chemical bonding of successive increments
of light-cured composite to each other.

23. 7. Packing and curing of resin composite:
Chemical-cured composites are supplied as
two paste system, while light-cured ones are
supplied as one paste packaged in tubes or in
pre-loaded compules or dispensing tips.
These dispensing tips are supplied with
syringe applicator to inject composite into
the cavity. Light-cured composites are
mainly polymerized by either Halogen light
curing unit or Light Emitting Diodes (LED).

26. • It has to be put in mind that the handling of
composite material is totally different than that of
amalgam, as composites are not condensable
because of their putty consistency tending to
stick to applicators and condensing instruments.
Hence, Teflon or Gold-plated packing
instruments have to be used. Dragging and
flushing of the composites towards the walls and
margins of the cavity during shaping of the
restoration, prior to curing, is mandatory to
increase its adaptation. This can also be done
with fine brushes that also smoothens the
composite increment surface.

28. Thank You