Repair of esthetic restorations [autosaved]

Repair of esthetic restorations
10/21/2019
Dr.Sherif sultan,BDS,MSc,PhD,Fixed
prosthodontics
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Indications
1. When the extent of the fracture
does not recommend the
replacement of the restoration.
2. To conserve tooth structure,
cost and time.
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Advantages
• Restores function and esthetic in an easy,
inexpensive and rapid form.
• Removes pain and discomfort associated with
replacement of fractured prosthesis.
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Causes of fracture of porcelain
intraorally.
• Contamination and other errors in fabrication(Improper
design, micro defects within the material.);
• Incorrect treatment planning with inappropriate use of the
material, notably in relation to the occlusion, and failure to
create sufficient space for the restoration.
• Incompatible thermal expansion coefﬁcient between the
porcelain and metal substructure.
• Seating force during insertion.
• Trauma.
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Techniques for repair
1- The direct technique (intra oral).
• It is done by the use of what is commercially known as porcelain
repair kits (e.g- Ultradent R Porcelain Repair Kit , Ceram-Etch kit and
Co jet porcelain repair kit).
• The porcelain repair kit mainly contains a surface treatment
material , coupling agent ,bonding agent and then composite is
applied directly to the fractured restoration.
• Advantages
• Less chair time, lower cost, and ease of application.
• Disadvantages.
• Low strength, poor wear qualities.
• Poor esthetic appearance due to lack of translucency or shade-
matching to the remaining teeth.
• Long-term success especially in load bearing surfaces is
unpredictable.
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2. Indirect technique (extra oral or laboratory).
• Porcelain is applied as a laboratory procedure.
• Advantages.
1.Better esthetics due to match between repair
porcelain and remaining porcelain.
2.High wear resistance.
Disadvantages
cost and time
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prosthodontics
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Repair of PFM restorations
1.Indirect repair.
• 2 techniques:-
• A- PFM overcastting.
• -used to repair fractured pontics.
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prosthodontics
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• Steps:-
• remove porcelain from the pontic using
carbide burs to provide adequate space for
the metal overcastting, opaque material and
porcelain.
• Impression.
• Make overcastting which should be rigid and
thin using non precious alloy.
• Apply porcelain to the over casting, which is
then tried intraorally, stained and glazed.
• Cement the PFM overcastting.
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B. PFM pin retained casting.
- Used in case of fractured porcelain facing
(porcelain on labial surface only).
- All porcelain is removed and a feather edge
margin is created along the entire labial surface of
the metal framework.
- Make parallel tapered pinholes using tapered
fissure bur.
- Make rubber base impression.
- Fabricate pin retained PFM restoration.
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2- Direct repair.
• Traditionally relied on mechanical
roughening of the fractured surface, followed
by application of a silane coupling agent to
enhance the resin -to-porcelain bond.
• Since direct repair of fractured PFM
restoration is made by resin composite, we
should know the nature of bond between
resins and (metals or ceramics.)
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prosthodontics
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Resin to metal bond
• In order to improve the bond between the metal and the resin a number of
different approaches have been explored.
1- Macro mechanical bonding.
• It depends on macroscopic features in the metal framework to give retention
to the resin (e.g:- roughening with a diamond or making undercuts).
2- Micro mechanical bonding (electrolytic etching of metal with hydrofluoric
acid).
This technique is only applicable to Ni- Cr or Co-Cr alloys, which have a
eutectic(multiphase) microstructure
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3- Chemical modification of the alloy surface.
A. Tin plating
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Intraoral tin plating. A, Tin-plating system in which direct current is used to
deposit tin from an amide solution (Micro- Tin Materilas). B, The system in
use intraorally. Note the gray color change. The tin is being deposited from
the solution and carried to the metal in the cotton pledget affixed to one
electrode of the plater; the circuit is completed with the alligator clip, which
is in electrical contact with the prosthesis.
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B. Tribochemical silicoating(Co jet
system)
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C. Metal Primers
• They are usually supplied as single-liquid primers
composed of a polymerisable monomer in a suitable
solvent. (The products are invariably called primers
despite them being in fact coupling agents.)
• The monomer has a bifunctional structure with one
end carrying a methacrylate group for resin bonding
and the other end carrying mercapto or thiol (-SH)
groups for bonding to the precious metal alloy.
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4- chemically adhesive resins.
• In order to improve the adhesive bond of
resins to the metal surface, a variety of dual-
cure composite resins have been developed in
which the resin component has been modified
to provide the ability to bond chemically to
suitably prepared metal surfaces. These resins
are generally referred to as chemically
adhesive resins to differentiate them from the
simple Bis-GMA type resins.
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• Examples
1. C&B Metabond (Parkell, Farmingdale, NY), in which the active
constituent is the carboxylic monomer 4-META (4-methacryloxy-
ethyl trimellitate anhydride), which has been demonstrated to
adhere to all types of metal alloys as well.
2. Panavia 21 resin cement (Kuraray Co, Osaka, Japan). In which
the active ingredient is a phosphorylated methacrylate monomer
such as MDP (methacryloxyethyl-phenyl phosphate).
Resin bonding is facilitated by the high affinity of
carboxylic acid or phosphoric acid derivative
containing resins for the metal oxide on the base
metal alloy.
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Resin-to-ceramic bond
• The resin-to-ceramic bond is based on an acid
etchant creating a micromechanically retentive
surface and a coupling agent providing the
chemical bond to the ceramic.
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-Hydrofluoric-Acid Etching.
• -concentrations :- 2.5-10%,liquid or gel form.
• -etching time :- 1-4 minutes.
• -Mechanism of action:- attacks the glass phase of
ceramic leaving a honeycomb – like surface.( This
process is generated by the preferential chemical
reaction between hydrofluoric acid and the silica phase
of feldspathic ceramics forming a salt named
hexafluorosilicate, which is removed by water spray.)
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-Silane coupling agents.
• Organo-silanes, generally referred to simply as
“silanes” in dentistry, are compounds that contain
a silicon (Si) atom or atoms, and display dual
reactivity. One end of a silane molecule is
organically functional (e.g.,vinyl–CH CH2,amino–
NH2),and can polymerize with an organic matrix
(e.g.,a methacrylate) in the composite.The other
end is generally comprised of alkoxy groups
(e.g.,methoxy–OCH3,ethoxy OCH2CH3), which
can react with a hydroxylated surface, like
porcelain.
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CONCLUSION
• N.B:-In general direct repair of PFM
restorations includes:-
• When metal infrastructure exposed,
sandblasting with alumina or alumina
modified with silicic acid+ silane+ adhesive
resin+ composite.
• When fracture is adhesive in porcelain only,
etching with hydrofluoric acid+ silane+
adhesive resin+ composite.
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Direct repair of all ceramic
restorations.
1- Repair of silica based ceramics
• In general it involves:- etching with hydrofluoric acid+
silane+ adhesive resin+ composite.
2- Repair of zirconia ceramics (non silica based ceramics).
• All-ceramic systems, in particular when used for bridges,
have mostly a two-layer structure consisting of a high
strength ceramic substructure core and a weaker
veneering ceramic layer.
• -Core fracture
It is rare because of high strength, if occur replace the
restoration.
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-Veneer fracture.
• If the fracture is in the veneer only make etching
then silane then bonding agent then composite.
• If the core is exposed it may be etachable (contains
silica) then make the same steps
• If the core is not etchable as zirconia , it will be a
problem. As most of zirconia is not etchable
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-Problems in repair of zirconia.
• 1- Zirconia is not readily etched by HF, and
requires very aggressive mechanical abrasion
methods to increase surface roughness, possibly
creating strength reducing surface ﬂaws,
Therefore, alternate surface treatment methods
are required for zirconia ceramics.
• 2-The lack of silica also removes the chemical
bonding between silica–silane necessary for
silanization. But this problem was solved by
tribochemical silica coating mentioned previously
which can be applied also to zirconia.
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Novel surface treatment methods of
zirconia.
1. Glass micro pearls.
2. Selective infiltration etching (SIE).
3. Laser irradiation.
4. Nanostructured alumina coating.
5. Internal coating with porcelain.
6. Pyrosil pen technology (SurA Instruments,Jena,
Germany).e.g:- Silano pen.
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The most important thing before doing
repair
• is TO REMOVE THE CAUSE OF
FRACTURE AND TO TELL THE
PATIENT THAT REPLACEMENT
IS BETTER THAN REPAIR.
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prosthodontics
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Repair of esthetic restorations [autosaved]

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