5. Porcelain fused to metal
Distortion of metal-ceramic framework
Inadequate metal support
Excessive porcelain thickness
Technical flaws
Normal function (occlusal forces)
Trauma
6. Failure of solder joints
Inclusion
Failure to bond
Small solder joint
15. Casting difficulties
External angles of crown
should be rounded
Sharp edges
Stone die
wax-up stage.
investment material flow
difficult to remove the investment material
Cement thickness
16. REPAIRMENT TIME…
Some things are really beautiful!
But nothing lasts forever!
HOW CAN WE REPAIR THESE C&B FAILURES?
17. Seriousness of the problem
1. Leave it alone if not causing any serious harm
2. Adjusting or repairing the fault
3. Replace the crown or bridge
19. Grinding and polishing in situ
Metal margins of crowns with positive ledges
Porcelain margin
Heatless stone
Diamond point
Followed by various composite finishing burs and discs.
20. Metal margins
1. Diamond stone
1. Green stones
2. Tungsten carbide stones
3. Metal and linen strips
2. Interdentally,
1. Triangular shaped diamond
2. Abrasive rubber instrument with special handpiece
3. Margins should be polished
21. Repairs by restoring in situ…….
Occlusal Repairs
1. Amalgam
2. gold inlay
3. composite material
22. Repairs at the Margins
margins of a poorly fitting bridge
Secondary caries/early erosion and abrasion
composite or GIC
Cavity prep at margins
poor access >>> remove part of the crown margin
raising a full gingival flap
good visibility
23. Repairs to porcelain
Ceramic restorations
Composite
Separate silane coupling agent
Limited to sites with minimal occlusal forces.
24.
25.
26.
27.
28.
29. Ceramic facings
Porcelain is lost and
composite repair is not
possible
Often better to replace
whole crown
Pontic.
Drilled through
New pin retained metal-
ceramic facing
Removing all the porcelain
Metal ceramic sleeve
crown
30. Removing c&b’s
1. Vibration of
ultrasonic scaler.
2. Good leverage at
margins
3. A slide hammer Bridge
remover
4. Crown can be cut off
31. Removing post & cores
Using extraction forceps and using sharp twists –
carefully…
Files
Ultrasonic
32. Removing PJC’s
Cannot be removed intact
and should be cut off.
A vertical groove is made
with a diamond bur in the
buccal surface just
through to cement.
Then Removed with
suitable heavy duty
instrument.
33. Removing Metal – Ceramic Crowns
Possible to remove with
normal devices
usually better to cut off.
cast metal
solid tungsten carbide bur
with very fine cross cuts
Eye protection!!!
Vertical groove cut on buccal
metal is usually thinner here
with better vision.
Diamond bur can cut
porcelain favourably !
35. Removing Bridges
(3 situations)
1. Abutment teeth need to be
extracted
Bridge is removed Intact
Dividing the bridge
2. abutment needed to be
retained
Retainers are cut and bridge
removed carefully
3. temporary measures
removing whole bridges and
making adjustments.
36.
37.
38.
39. Inhibited or Slow Setting
Visual Appearance:
Shiny, no detail
Result:
Inadequate surface detail on
cast, poor fitting restorations.
S ulfur inhibition For Vinyl
Polysiloxane Materials
latex gloves .
Residues
custom temporary
provisional cements
40.
41. Inhibited or
Slow Setting
CAUSE SOLUTION
For Vinyl Polysiloxane
Materials
Sulfur inhibition due to
contact of latex gloves with
tissue/tooth/retraction
material or impression
material.
Wear gloves proven not to
contain traces
of sulfur.
If contamination is
suspected, scrub affected
area with diluted hydrogen
peroxide.
42. Inhibited or Slow Setting
CAUSE SOLUTION
Residues from custom
temporary or
provisional cements (acrylics)
present.
Do not use impressions already
used to
fabricate the temporary
restoration.
Fabricate the temporary crown
or bridge
after final impression has been
made.
Remove air-inhibited layer on
the exposed
surface with an alcohol wipe
before making
final impression.
44. Lack of Impression Detail
Visual Appearance:
Muted detail
reproduction.
Result: Crowns may be
too tight, or loose, and
not fit correctly.
45. Lack of Impression Detail
CAUSE SOLUTION
Impression material stored at
elevated temperature.
Store impression material at
room temperature.
46. Lack of Impression Detail
CAUSE SOLUTION
Impression material stored at
too low a temperature
(prolongs the setting
reactions,
changes viscosity and
requires exceptionally
high extrusion forces for
automix materials).
Keep impression material at a
temperature of
18°C/64°F at least one day
prior use.
47. Lack of Impression Detail
CAUSE SOLUTION
Thick blood/saliva pooled
around prep.
Remove blood and saliva
prior to
making impression.
Use 2-step impression
technique.
48. Lack of Impression Detail
CAUSE SOLUTION
Inadequate retraction of
sulcus around prep.
Use good retraction
technique, with proper
moisture control.
49. Lack of Impression Detail
CAUSE SOLUTION
Exceeding the working time. Follow manufacturer’s
working
time specifications.
Choose material with longer
working time.
50. Lack of Impression Detail
CAUSE SOLUTION
Inadequate disinfection
effects
surface quality (detail
reproduction) and
dimensional stability.
Use water based disinfectants
according to
FDA guidelines.
Follow manufacturer’s
instructions for use.
51. Voids on the Margin
Visual Appearance:
Voids/holes on margin
of the prepared teeth.
Incomplete margin.
Result: The fit and
function of the final
restoration may be
compromised. Short
crown margins
and/or open margins.
52. Voids on the Margin
CAUSE SOLUTION
Improper syringe technique. Keep syringe tip immersed in
wash material to
avoid entrapping air.
Wiggle and stir while
syringing. Push
material forward.
53. Voids on the Margin
CAUSE SOLUTION
Inadequate coverage of
marginal area with light body
impression material.
Use wash material liberally
on preparation
and abutments.
54. Blood and saliva
contamination around prep.
Use good moisture control technique.
Rinse and dry prep area before taking
the impression.
Stop bleeding by using appropriate
retraction
technique and hemostatic agent.
Leave cord
in sulcus until no blood or saliva are
present
before syringing the light body
impression
material. Consider two-cord retraction
to
displace tissue and control fluids.
Voids on the Margin
CAUSE SOLUTION
56. Tearing at the Margin
Visual Appearance:
Rip, or visible tearing
on the margin of the
preparation.
Result: Short crown
margins and/or open
margins.
57. Tearing at the Margin
CAUSE SOLUTION
Check expiration date of
impression material.
Ensure mixing instructions
are followed and materials
have a streak-free appearance.
Expired impression material.
Inadequate mix.
58. Tearing at the Margin
CAUSE SOLUTION
Displace tissue to allow the
impression material to access
prepared area.
Consider two-cord retraction.
Leave pilot cord in the sulcus
when taking the impression.
Use impression material with
sufficient tear resistance.
Insufficient retraction.
59. Tearing at the Margin
CAUSE SOLUTION
Do not use impressions
already used to fabricate the
temporary restoration.
Fabricate the temporary
crown or bridge after final
impression has been made.
Remove air-inhibited layer on
the exposed surface with an
alcohol wipe before making
final impression.
Residues from custom
temporary or provisional
cements (acrylics) present.
60. Facial-Lingual Pulls
Visual Appearance: V-
shaped void, trough-
like.
Result: Failure to
capture complete and
accurate dentition.
61. Facial-Lingual Pulls
CAUSE SOLUTION
Follow manufacturer’s
working time specifications.
Choose material with longer
working time.
Exceeding the working time.
64. Facial-Lingual Pulls
CAUSE SOLUTION
Use lingual stops.
Use an impression tray that
supports the flow
of the material.
Impression tray does not
support flow of
impression material.
65. Tray-Tooth Contact
Result: Restoration
may have slight
distortion at marginal
area, or rocks.
Visual Appearance:
Show-through of tray.
Impression tray
exposed.
66. Tray-Tooth Contact
CAUSE SOLUTION
Use proper size tray.
Test various tray sizes to
ensure proper size.
Prepared teeth contact the
sides or bottom
of impression tray.
67. Tray-Tooth Contact
CAUSE SOLUTION
Carve out tray material
properly before
applying wash.
Tooth contact with the pre-
set tray material
when using the two-step
technique.
70. Delamination
CAUSE SOLUTION
Follow manufacturer’s
working time specifications.
Choose material with longer
working time.
Store impression material at
room temperature.
Exceeding the working time.
Impression material stored at
elevated temperature.
71. Delamination
CAUSE SOLUTION
Avoid contact with sulfur
contaminants:
Wear gloves proven not to
contain traces of sulfur.
Avoid contact with acrylic
and methacrylic
contaminants:
Ensure impression
materialdoes not come into
contact with methacrylate
residue from acrylate
temporary materials.
Sulfur or acrylic
contamination of pre-set
heavy body material in two-
step technique.
72. Poor Bond of Impression
Material to the Tray
Visual Appearance:
Impression pulling
away from the
sides/bottom of tray.
Result: Crown(s) may
be tight and not seat
fully, or require
excessive internal
adjustment.
73. No tray adhesive used. Use tray adhesive.
Poor Bond of Impression
Material to the Tray
CAUSE SOLUTION
74. Incompatible tray adhesive
used.
Use appropriate tray
adhesive.
VPS adhesive for VPS.
Polyether adhesive for
polyether materials.
Poor Bond of Impression
Material to the Tray
CAUSE SOLUTION
75. Inadequate drying time for
tray adhesive..
Follow manufacturer’s
instructions for application,
and drying time
Poor Bond of Impression
Material to the Tray
CAUSE SOLUTION
76. Thin plastic trays allow
deflection, which can cause
rebound upon removal.
Use a tray that fits better, and
is stiffer and more rigid.
Poor Bond of Impression
Material to the Tray
CAUSE SOLUTION
77. Stone Model
Discrepancies
Visual Appearance:
Voids on margin,
powdery cusp tips on
incisal edges on
prepared tooth. “Golf-
ball” appearance of
stone model.
Result: Incomplete
seating of indirect
restorations
79. Tooth contact with
impression tray, or gauze of
double bite tray causes water
to leach out of the tray,
dehydrating the stone.
Instruct patient to bite
passively in centric occlusion
when using dual arch trays.
Fill tray with sufficient
amount of material.
CAUSE SOLUTION
Stone Model
Discrepancies
80. Cast not made according to
model preparation guidelines
and lacks detail.
Provide as much information
as possible to the lab.
Indicate
type of impression material
(polyether or VPS) and
whether
or not the impression has
been disinfected.
CAUSE SOLUTION
Stone Model
Discrepancies
81. VPS
Hydrogen gas emission.
Follow manufacturer’s
instruction for casting time.
CAUSE SOLUTION
Stone Model
Discrepancies
Editor's Notes
Failure means, to be unsatisfactory, and in C&B, it’s the inevitable.
Repairment is the work that is done to get rid of the failure.
Distortion of metal-ceramic framework invariably results in the loss of porcelain
A flaw or inclusion in the solder itself
Failure to bond to the surface of the metal
The solder joint not being sufficiently large for the conditions in which it is placed.
Progression of perio disease
Abutment tooth may become non-vital (pulpal problems)
Recurrent caries occuring at margins of retainers:
- change in diet.
- lapsed oral hygiene.
- inadequate restoration
design
May occur to all-metal bridges
if pontics are too thin or
if a bridge is removed with too much force.
Framework distortion may occur during function or as a result of trauma.
Crowns tend to wear down substantially over a lifetime
All restorative materials wear in use
, and the rate is determined by the occlusion,
the diet and parafunctional (bruxing) habits
No cut back
Inadequate space for porcelain
Minor problems to be noted & monitored but where no other action is needed.
The type of inadequacies that can be corrected in situ.
Those that cannot.
Positive ledge (overhang)
excess of crown material protruding beyond the margin of the preparation.
Negative ledge
deficiency of crown material that leaves the margin exposed but with no major gaps between the crown and the tooth.
Often arises because the impression did not correct at the try-in stage.
“External angles of crown preps for metal castings should be rounded to prevent one of the faults that may occur in the following chain of events:”
Stone die may not flow into the impression adequately, trapping air bubbles in the sharp angles of the imp.
Sharp edges may be damaged at the wax-up stage.
Investment material may not flow adequately into the wax pattern to produce rounded internal angles on the casting, preventing the casting from seating fully.
It may be difficult to remove the investment material entirely from sharp internal angles without damaging the casting.
Cement will flow less rapidly around sharp angles, increasing the likelihood of an unnecessary thick cement layer at the margins.
Flower picture
In some situations, margins of crowns with good ledges can easily be adjusted.
If margin is porcelain (or specially designed), finishing instruments should be used, example, heatless stone or diamond point followed by various composite finishing burs and discs. Can also be modified in situ using the same instruments.
diamond stone followed by green stones, tungsten carbide stones or metal and linen strips may be used.
Interdentally, a triangular shaped diamond and an abrasive rubber instrument with special handpiece (esp overhangs).
Margins should be polished with prophylactic paste with brush/rubber cup, and interdentally with finishing strips.
Occlusal Repairs
Occlusal effects in metal retainers can be fixed by amalgam which usually gives good results.
A small gold inlay may also be preferred.
In metal-ceramic or porcelain restorations, composite material can be used but repair may need to be done periodically.
Should never try to repair margins of a poorly fitting bridge during insertion.
Secondary caries/early erosion and abrasion can be treated with composite or GIC.
Cavity prep at margins should not endanger strength although all caries should be removed. If poor access, then it is better to remove part of the crown margin rather than excessive amount of tooth structure.
In some cases, raising a full gingival flap may be justified.
Retainer margins can be adjusted and restored with good visibility.
Any necessary periodontal therapy or endodontic surgery can also be carried out.
Materials such as basic composite with a separate silane coupling agent for optimum bonding can be used to modify or shape ceramic restorations.
It is not an acid etch bond to enamel and is not strong. Therefore, the use of the material is limited to sites with minimal occlusal forces.
When porcelain is lost from a metal-ceramic unit and composite repair is not possible – often better to replace whole crown.
Sometimes possible with a pontic. A hole is drilled through the backing and an impression is taken with suitable pins for a new pin retained metal-ceramic facing.
- It could be a little bulkier than the original!
Sometimes possible to fix retainers or pontics by removing all the porcelain and reprepare the metal part using a “metal ceramic sleeve crown” which covers the skeleton of the old retainer or pontic.
Sometimes made with heat cured acrylic or laboratory light cured composite.
In removing any crown or bridge, in particular posts and caries, often helpful to break up the cement by vibration of ultrasconic scaler. It works best with zinc phosphate cement.
Metal crowns
Good leverage at margins for either complete or partial metal crowns.
Some instruments used are;
- cumine or mitchels trimmer
- even a slide hammer type crown
- bridge remover may be used
Crown can be cut off if all else fails.
Possible to remove with normal devices but are more rigid than gold and porcelain may break – usually better to cut off.
cast metal is best cut with a solid tungsten carbide bur with very fine cross cuts (beaver bur).
Eye protection is important for everyone
.
Vertical groove cut on buccal as metal is usually thinner here with better vision.
Diamond bur can cut porcelain favourably !
1 Abutment teeth need to be extracted
Bridge is removed with crown and bridge remover
Easy for cantilever
Others - Dividing the bridge through pontic or connector and remove teeth individually with retainers in place
2. When abutment teeth are needed to be retained either for support of partial denture or overdenture or for making a new crown. Retainers are cut and bridge removed carefully as preparations are protected.
3. Some temporary measures require removing whole bridges and making adjustments. Neither bridge nor preparation should be damaged.