Restorative Dentistry Fifth Year

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FAILURE OF RESTORATIONS
5 T H YEA R
2 012
Topic outline
 Criteria of successful restoration
 Factors affect the success and failure of restorations
 The success and failure of restoration attribution
 Failure of amalgam restoration
 Failure of cast restoration
 Failure of glass ionomer restoration
 Failure of composite restoration
 Failure versus repair
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 The restorative dentistry is provided with a wide
range of materials to restore any derangement of
lesion in hard tooth substances. These lesion
includes caries, erosion, attrition, traumatic fracture,
discoloration as well as minor abnormalities in form,
size alignment or occlusion of teeth .
Criteria of successful restorations
Objectives of operative dentistry:
1- stop of the original insult and prevention of its
recurrence.
2-restoration of function
3-restoration of esthetics
4-while maintaining the physiological integrity of the
teeth in good relationship with the adjacent hard and
soft tissues.
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Criteria of successful restoration:
 Regard to the objectives of the operative dentistry.
The successful restoration should fulfill
the objective beside to be durable, less
costly and easy to do.
Success and failure of restorations depend on many factors:
1- the degree of involvement
2-The skill of the operator
3- the properties and the limitations of the existing
restorative material and techniques.
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The success and failure of the restoration is attributed to:
 I- misjudgment in selection of the restorative material:
A. this selection should be based on logical and through
analysis of all variables including properties of available
restoratives, the demands and the limitations of the oral
environment and the past experience of the operator.
Ex. Both amalgam and gold serve satisfactorily as
individual restorations but if used in the same mouth ,
excessive tarnish, corrosion due to galvanic activities and
patient discomfort and pain maybe inevitable.
 II-Cavity preparation:
More than 60% of failure may be due to improper
cavity preparation. The design of the preparation
affect the mechanical integrity of both the tooth and
the restoration, the biological influences of the
restoration on the dentino-pulpal organ and also has
an important effect on the esthetic of the restoration.
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III-Material manipulation:
Incorrect material manipulation is responsible for
about40% of failure of the restorations.
IV-The nature of the oral environment:
1-Accessibility
2-The patient demands
3-The corrosive potentials
4-The aqueous nature
5-The thermal changes
6-The oral microbes
7-Forces in the mouth
Failure of amalgam restorations
I- Marginal degradation (ditching ):
Def: marginal degradation ,ditching, fracture or
crevicing refers to breakage of a thin edge of a
restoration creating an irregular V shaped crevice.
Causes :
1-Depletion of support at margins
2- Voids entrapment
3- Excess mercury
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1-depletion of support at margins:
Amalgam is a brittle material with low tensile and
shear strength so; it must be supported by tooth
structure.
 Depletion of support may be due to
Lack of support or insufficient bulk of material at
margins
 Lack of support may be due to:
excessive expansion caused by
----under trituration
----excess mercury
----moisture contamination
----age dependant changes in the
microstructure as creep.
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 Creep: Time dependant changes in the form of
amalgam under constant loads and temperature.
 Insufficient bulk at margins:
Strength of amalgam is essentially thickness
dependent .why?
Insufficient bulk may be due to:
---Beveling preparation
---Over carving
---Leaving thin marginal flashes.
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 2- Voids:
The presence of voids in amalgam decrease the density
and strength of the amalgam
Voids may be due to:
---corrosion
---to dry mix
---inadequate condensation
----moisture contamination of amalgam
 3-Excess mercury:
Excess mercury tends to decrease the strength of
amalgam.
Excess mercury may be due to:
---wrong proportioning of alloy/mercury ratio.
---under trituration .
---inadequate condensation force
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 Clinical picture:
All cavity margins are prone to ditching especially
buccal end of proximal marginal ridge appear like
irregular V shape crevice:
this wall should be prepared in the form of reverse
curve to provide CSA 90
How to prevent
1- follow the principle of cavity preparation
2-proper selection of the alloy
3-proper manipulation of the material
Treatment:
The actual treatment depend on the extent of ditching:
Very small
finishing of the margin
Moderate size
repair with cermet or bonded
amalgam
Gross ditching
total replacement of the restoration
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 II.Isthmus fracture:
 Def: Isthmus: it is the narrowest junction between
the occlusal and the auxiliary portion of the
cavity(buccal, lingual or proximal)
 Factors that attributed to isthmus fracture:
A .factors increase flexural stresses
---inadequate resistance form
---inadequate retention
---sharp angles or irregular surface
 B .factors decrease flexural strength:
---insufficient bulk of amalgam
---excess mercury
---structural discontinuities(corrosion, dry mix,
moisture contamination, improper condensation)
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 Clinical picture:
It start as crack line may be propagate and widened
with masticatory force
Hypersensitivity with eating and drinking
Food impaction
Recurrent caries
Periodontal irritation
 Treatment:
1- proper examination to understand the cause of
isthmus fracture
2-improve the resistance and the retention form
3-removal of any surface discontinuity.
4-selective grinding of opposing plunger cusp.
5-increase bulk of amalgam at this isthmus area by
rounding the axio-pulpal line angle .
6- proper handling and manipulation of the amalgam
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 III- Tooth fracture:
Def: fractured cusp or ridge under functional forces
Causes :
Amalgam lacks sufficient tensile strength to support remaining
tooth substance and much less able to reinforce weak cusps
and ridges
 Treatment :
1- eliminate all undermined enamel.
2-conserve the integrity of the remaining tooth structure
3-restore the very weakened tooth structural with inlay, onlay,
or even full coverage
 IV-Recurrent caries:
Def: Caries developed in previously restored tooth
Causes:
1- incomplete elimination of the lesion
2-improper outline form
3-improper restoration of the anatomy
4-rough surface retention of bacterial plaque
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 Clinical picture:
Carious lesion at the margin of the restoration or extend
deeper underneath the restoration.
 Treatment :
Prevention
adequate cavity preparation
conservative treatment of non carious pit
and fissures by enameloplasty, application of fissure
sealant.
Management
replacement of the restoration
repair of the marginal defects with
glass ionomer (cermet) or bonded amalgam
 V-Excessive discoloration:
 Clinical picture:
Tarnish
loss of surface luster
Corrosion
rough pitted amalgam surface
Amalgam blues
dark bluish discoloration
Tarnish :surface discoloration of amalgam with loss of its luster
Formation of a surface film of discoloring oxides and sulfides
 Causes:
excess Hg
under trituration
improper condensation
improper finishing
moisture contamination
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Corrosion :actual disintegration of the bulk of amalgam.
Chemical corrosion: due to lack of polishing and food
stagnation
Electric corrosion: setting of electromotive force between two
different electrodes (two dissimilar metallic restoration) likes
-old and new similar metallic restoration
-polished and unpolished areas of the same
restoration.
-the same restoration but heterogonous in structure
-accumulation of certain types of food on a site of
restoration making it different in its electric potential from
other sites of amalgam.
 Amalgam blues: the amalgam hues appear through the
enamel surface due to:
thin or undermind enamel.
penetration of metallic ions and corrosive products of
amalgam through the dentinal tubules.
 Treatment:
1- Tarnish requires repolishing
2- Corrosion may require replacement of old restoration
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 VI-Post restoration hypersensitivity:
 Hypersensitivity in a recently amalgam restored tooth may
be due to stimulation of freshly exposed dentine by:
Galvanic , thermal , chemical or premature contact.
 Clinical picture:
Pain occur in recent restoration
 Treatment :
Elimination of the cause
Application of desensitizing agent
Elimination of premature contact
 VII- Gingival and periodontal affections:
 Causes :
1- gingival overhangs
2-thick sub gingival margin
3-ragged cavity margins
4-rough margin restoration
5-open contact lead to food impaction
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 Clinical picture:
Gingival and periodontal inflammation with
increased tendency to bleeding
Discomfort
Tooth mobility
 Treatment:
Defining and removal of the cause
 VIII-Dislodgment of the restoration:
 Causes:
1- inadequate retention form
2- fracture of the restoration
3-fracture of the tooth
4- recurrent caries
Treatment :
Evaluation of the retention followed by replacing the
restoration
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Failure of cast restoration:
I-Recurrent caries:
 Causes :
1- fitting discrepancies
a. distortion of impression, dies, or wax
pattern.
b. incorrect compensation of casting shrinkage
leading to under or over sized restoration
c. roughness of the fitting surface
d. modification by grinding
2- Improper cementation:
a. high solubility
b. low strength
c. thick consistency
d. moisture contamination
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3- Under extension of cavity outline:
a. not include all defective pits and fissures
b. improper placement of the cavity margins in
self cleansable area.
4- Stagnation
of bacterial plaque:
a. due to lack of polish
b. presence of marginal overhangs
c. poor oral hygiene
Treatment :
evaluation of the cause followed by remake of the
restoration.
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II- Dislodgment of restoration:
Causes :
1-Inadequate mechanical retention due to over
divergence of the cavity walls
2- Recurrent caries
3- Improper cementation
4- Excessive torque by occlusal interference
5- Premature loading of the restoration
Treatment:
Evaluation of the cause and remake of the
restoration if needed.
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Failure of glass ionomer restoration:
I- Increased opacity:
Causes :
1- dehydration and biodegradation by oral fluids
2- inadequate powder /liquids ratio
3- injudicious finishing
4- incorporation of air voids
II- Loss or dislodgment of the restoration:
Causes :
1- moisture contamination
2-premature setting
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Failure of composite restoration:
I- post operative hypersensitivity:
Dentin hypersensitivity is more frequently to occur
with Class II,V composite restoration as a result of:
1- leakage
2- cusp deflection by polymerization shrinkage
stresses.
Treatment :
Replacement or repair of the restoration
II- Recurrent caries:
Causes :
1-marginal leakage due to polymerization shrinkage
2-rough restoration surface due to low wear resistance
of the composite restoration
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Clinical picture:
If catching discrepancies are identified in a composite
restoration, recurrent caries must be expected
Treatment :
Repair or replacement of the restoration.
III- Cyto-toxic pulp reaction:
Pulp reaction occur more frequently under composite
restoration that may be due to steps of application
(acid etching, bonding agent)
Or the chemical composition of the composite material
itself and its toxic effect on the pulp.
Bacterial invasion associated with the leakage is the
first cause of pulp inflammation
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This is accompanied with the sign and symptoms of
reversible or irreversible inflammation
These reactions did not occur immediately after
placement
Treatment :
The restoration must be replaced
IV- Discoloration:
1- incorrect color determination
2- marginal discoloration
3- surface discoloration
4-bulk discoloration
Treatment :
It essential depend on the extent of the discoloration
and generally ranges between resurfacing, veneering
or total replacement.
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V- Dislodgment of restorations:
Causes :
1- Improper application of the adhesive system
2- Excessive force
Treatment :
Total replacement of the restoration
Proper application of the adhesive system
VI-gross fracture:
Causes:
Composite is a brittle material with low flexure
strength
Similar to amalgam restoration , fracture may result of
unbalance between flexure strength of composite
and flexure stresses developed in the restoration
Treatment:
Repair or total replacement
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VII- Biodegradation:
Causes :
It is gradual break down of the material in the oral
environment with biological activity
It includes disintegration and dissolution in saliva, as
well as other types of chemical/physical degradation
such as wear
Bio-degradation rate accelerated with acidic media
(bad oral hygiene).
Treatment :replacement of restoration

Thank you
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