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7/28/2019 Resto Sem Report Common Errors
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Failures of Amalgam
CAUSE EFFECT
Too shallow cavity
Thin AmalgamToo thick cavity liner
Too thick cement base
Inadequate cuspal reduction
Thin Amalgam (over the cusp)
Giving cavosurface bevel
Sharp axio-pulpal line angle
Stress Concentration
(isthmus)Sharp angles in occlusal
outline form of Class II
Fracture of the Restoration
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Failures of Amalgam
CAUSE EFFECT
Sloping gingival step
No Resistance Form(isthmus)
Too narrow gingival step
Insufficient Hg
Weak AmalgamExcess Hg
Undertrituration
Moisture contamination
(Zn having alloys)
Delayed Expansion
(flow over margins)
Fracture of the Restoration
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Failures of Amalgam
CAUSE EFFECT
Insufficient condensation pressure
Increased Residual HgNot squeezing out excess Hg
Mix squeezed too dryLack of Cohesion
(amalgam weak)Condensation of partially crystallized amalgam
Overfilling Thin Amalgam Over Margins
Failure to warn patient not to chew on the
restoration for first few hours
Early Strength Not High EnoughFailure to support proximal part of the restoration
while removing matrix band
Fracture of the Restoration
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Failures of Amalgam
CAUSE EFFECT
Sharp angles in occlusal outline
of Class IIStress concentration
Excess removal of tooth structure
Enamel undermined and
tooth weakened
Fracture of the Tooth
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Failures of Amalgam
CAUSE EFFECT
Absence of undercuts No retention form
Dovetail with only one cornu No resistance to dislodgement
Too thick liner that is lost
subsequentlyLack of adaptation to cavity walls
Using large condensers initiallyUndercuts and margins not filled
- No retention
Inadequate Retention
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Failures of Amalgam
CAUSE EFFECT
Excess Sn (tin) in the alloy Too much shrinkage
Overtrituration Shrinkage on setting
Excessive pestle pressure Slow setting with shrinkage
Failure to condense towards margins Marginal gaps
Using large condensers initiallyDeficient margins and
undercuts
Carving from amalgam to tooth Marginal defects and gaps
Excess amalgam left beyond
cavosurface angles
Breaks away leaving deficient
margins
Marginal Leakage
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Failures of Amalgam
Porous and Weak Amalgam
CAUSE EFFECT
Increased 2 Phase (low Cu alloys) Weak phase
Irregularly shaped particles in the alloy Porosities and voids;less coherence of phases
Too less Hg Same as above
(Incomplete amalgamation; non-plastic)
Too much Hg Increased residual Hg
(Increased 2Phase , decreased 1 Phase phases)
Undertrituration Porosities & voids
Trituration beyond limits Decreased coherence(due to cracking of crystals)
Delayed insertion after trituration
Porosities and voidsInsertion of too large increments
Decreased condensation pressure Porosities and voids
(increased residual Hg)
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Failures of Amalgam
Porous and Weak Amalgam
CAUSE EFFECT
Moisture contamination Porous amalgam
Mix squeezed too dry Decreased coherence
Mix not squeezed (with high Hg:Alloy ratio) Porosities and voids
(increased residual Hg)
Condensation of partially crystallized amalgamPorous amalgam
Condensing with serrated pluggers with set
amalgam in the serrationsOld amalgam contaminates restoration and
weakens itOverheating while polishing 'Burns' amalgam and releases H
resulting in porosity
Burnishing set amalgam Breaks up superficial crystalline structure
releasing Hg causing porosity
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Failures of Amalgam
Tarnish and Corrosion
CAUSE EFFECT
Alloy with excess 2 Phase Has least resistance to corrosion
Fissures carved too deep Food stagnation leading to tarnish and
corrosion
Failure to polish Rough surface causing crevicularcorrosion
Contact with dissimilar metallic
restoration Galvanic corrosion
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Failures of Amalgam
Gingivitis and Periodontitis
CAUSE EFFECT
No wedge used Gross overhang;
Contact area deficiency
Surface left high in biteHigh point causing periodontitis
Failure to polish proximalsurface
Food stagnation resulting in gingivitis and
periodonitisLack of proximal contact
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Failures of Amalgam
Lack of Functional Efficiency
CAUSE EFFECT
Fissures carved too deep
Reduced masticatory efficiencyUnderfilling
Failure to carve Decreased masticatory efficiency(tooth anatomy not simulated)
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Failures of Amalgam
Pain after Placing restoration
CAUSE EFFECT
Failure to use liner and base Thermal conduction
Overfilling High point causing periodontitis resulting in pain
Moisture contamination Delayed expansion with pressure on pulp
Increased Hg: alloy ratio Mercuroscopic expansion with pressure on pulp
Failure to squeeze out excess Hg
Mercuroscopic expansion(increased residual Hg)Inadequate condensation pressure
Cavity preparation without water coolant
Pulpitis resulting in painMicroscopic pulp exposure
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Sometimes, excess Hg within the restoration may seep
through the dentinal tubules, discolor dentin and result
in blackish or grayish staining of teeth.
Since enamel is semi- translucent, this discoloration is
not inconspicuous.
Failures of Amalgam
Tooth Discoloration
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most commonly carried out using volumetric dispensers or
preproportioned capsules
the advantages of the latter are:
o that the dentist does not have to worry
about getting the right ratio of alloy to
mercury
(as this is prefixed by the manufacturer)
o that there is less danger of mercury
spillage during the handling stages of
amalgam placement
unfortunately, the capsules are more expensive than
buying the alloy powder in bulk
Proportioning
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TRITURATION
adequate trituration is essential to ensure a plastic mix and
thorough amalgamation
trituration time needed is dependent upon both the type of
alloy being used and the dispensing and mixing system
trituration times affect the dimensional changes that occur
when amalgam sets
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most important demands on the condensation technique are:
that as much excess mercury is removed as is possible
that the final restoration will be non- porous
that optimum marginal adaptation is achieved so as to
prevent postoperative sensitivity
important components in condensation are:
the use of maximum force
the use of suitably sized condensers in relation to
cavity size
the use of multiple and rapid thrusts
the placement of small increments.
CONDENSATION
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burnishing more recent studies indicate that the overall effect of
burnishing is to:
increase surface hardness
reduce porosity and decrease corrosion
improve the marginal adaptation of the amalgam
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Over filling, under filling, and over carving
if a cavity is overfilled and is not then carved back
sufficiently to provide a smooth transition from the tooth
surface to the restoration surface, a ledge will result
this ledge will eventually fracture, and give the appearance
of marginal breakdown of the restoration
under filling or over carving can result in an acute amalgam
margin angle that will give rise to marginal breakdown
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Fracture Lines
Marginal Ditching
Proximal Overhangs
Poor Anatomic Contours
Failures of
Amalgam Restorations
Signs of Failures
Marginal Ridge Incompatibility
Improper Proximal Contacts
Recurrent Caries
Poor Occlusal Contact
Amalgam Blues
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Amalgam Tattoo
accidental implantation of silver containing compounds
into oral mucosal tissue
occurs:
removal of old amalgam
broken pieces entering socket (tooth extraction)
particles entering surgical wounds
amalgam dust in oral fluids (abrasion areas)
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Amalgam Tattoo
common sites:
gingiva
buccal mucosa
alveolar mucosa
seen as grayish black pigmentation
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GlC sets within 6- 8 minutes from the start of mixing
setting can be slowed when the cement is mixed on
a cold slab
this technique has an adverse effect on strength
conventional glass ionomer restorations are difficult to
manipulate as they are sensitive:
to moisture imbibitions during the early setting
reaction
to desiccation as the materials begin to harden
Failures of g. i. c.
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secondary or marginal caries
most common failure of glass ionomer
restorations
7 years
median age of restoration failure for
glass ionomer
Failures of g. i. c.
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Failures of composite resins
Undercured Composites
brighter light means deeper and faster curing
of the composite
many older lights are not bright enough to cure
the full depth of a posterior composite filling
can be solved by filling the tooth in thin
increments and curing each incrementthoroughly before placing the next increment
newer arc lights and laser curing units are so bright
that they can cure to a greater depth quite quickly
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Failures of composite resins
Undercured Composites
the tooth will remain sensitive for a very long time
only solution for this problem is toremove the filling and replace it with aproperly cured composite or an amalgam
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Failures of composite resins
Shrinkage Stress
plastics tend to shrink when they transform from theliquid to the solid phase
(similar to the way water tends to expand when frozen)
microscopic shrinkage always happens
can cause the vertical walls of the
preparation to be drawn together whichcan produce prolonged sensitivity to cold
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Failures of composite resins
Shrinkage Stress
slicing
a simple technique used to release the stress
the dentist cuts a vertical groove from the top
of the filling to the floor of the preparationfrom mesial (front) to distal (back) throughthe filling
this allows the cusps on either side to rebound
relieving the stress
the groove is then refilled with composite and
the filling is then as good as new
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Failures of composite resins
Shrinkage Stress
the use of clear plastic matrix bands
another way to avoid shrinkage away
from the walls of the prep
allows the curing light to be directed
through the plastic from the side of
the tootho this would cause the composite to be
drawn toward the cavity prep wallsand eliminate the shrinkage away
from them
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Failures of composite resins
Shrinkage away from the Floor of the
Cavity Preparation
composite tends to shrink toward the light
since the light source is usually directed
from the top of the tooth
often causes the filling material to pull
away from the floor of the cavitypreparation allowing a tiny void to formunderneath the filling between thebottom of the filling and the tooth surface
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Failures of composite resins
Shrinkage away from the Floor of the
Cavity Preparation
the void eventually fills with fluid and cancause hydrostatic pressure in the dentinaltubules which leads to sensitivity to pressureon the filling
this is the most common reason for pain when
biting on a newly done composite filling
only solution for this problem is to redo
the filling
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Failures of composite resins
Shrinkage away from the Floor of the
Cavity Preparation
the dentist can often avoid this problem:
o by placing the composite in increments
that cover only part of the floor
o by the use of a self curing glass ionomerbase used under the composite
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Failures of composite resins
White line or halo around enamel
margin (microfracture of marginal
enamel)
Causes:
1. Traumatic contouring or finishing
techniques2.Inadequate etching and bonding of the
area
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Failures of composite resins
White line or halo around enamel
margin (microfracture of marginal
enamel)
Solution:
1. Re-etch, prime, and bond the area2.Conservatively finishing techniques (lightintermittent pressure)
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Failures of composite resins
Voids
Causes:
1. Mixing of self cured composites2.Spaces left between increments during
insertion3. Tacky composite pulling away from thepreparation during insertion
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Voids
Potential Solutions:
1. More careful technique
2.Repair of marginal voids by preparingthe area and re restoring
Failures of composite resins
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Failures of composite resins
Weak or missing proximal contact
Causes:
1. Inadequately contoured matrix band2. Inadequate wedging, both preoperatively and
during the composite insertion
3. Tacky composite pulling away from matrix contactarea during insertion
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Failures of composite resins
Weak or missing proximal contact
Solution:
1. Properly contour the matrix band2.Have matrix in contact with adjacent
tooth3.Use firm insertion wedging technique
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Incorrect Shade
Failures of composite resins
Cause:
1. Inappropriate operator lightning while selectingthe shade
2. Selecting the shade after the tooth is dried
3. Shade tab not matching the actual compositeshade
4. Wrong shade selected
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Failures of composite resins
Incorrect Shade
Possible solutions:
1. Use natural light if possible2. Select the shade before isolating the tooth3. Preoperative place some of the selected shade on
the tooth and cure (then remove)4. Do not shine operating light directly on the area
during shade selection