Download - Fixed prosthodontics problems and solutions
Problem solving in fix prosthodontics
INTRO……. Failure
Repairment
About 90% of bridges last at least 10 yrs.(Smith, 2000)
WHY C&B WORKS FAIL? MECANICAL FAILURE
CHANGES IN ABUTMENT TOOTH
DESIGN FAILURES
INADEQUATE CLINICAL OR LAB TECHNIQUE
Mechanical Failures…. Porcelain/PJC
Failure of solder joints
Distortion
Occlusal/Incisal wear & perforation
Lost facings
Porcelain fused to metal Distortion of metal-ceramic framework
Inadequate metal support
Excessive porcelain thickness
Technical flaws
Normal function (occlusal forces)
Trauma
Failure of solder joints Inclusion
Failure to bond
Small solder joint
CHANGES IN ABUTMENT TOOTH…. Perio disease
Pulpal problems
Recurrent caries
Mutiple aboutment better to index and solder
Mutiple aboutment better to index and solder
Distortion Pontics are too thin
Bridge is removed with too much force.
Trauma.
Occlusal/incisal wear & perforation Composite crowns
Belle glass
Targis vectris
Wear down substantially over a lifetime
Rate
Occlusion
Diet
Para functional (bruxing) habits
3) DESIGN FAILURES….. Abutment prep. design
Inadequate bridge design
Under-prescribed bridges
Inadequate clinical/lab technique Problems to 1 of 3 groups:
1. Minor problems
2. Can be corrected in situ.
3. Those that cannot.
Marginal deficiencies Positive ledge (overhang)
Negative ledge
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
REPAIRMENT TIME…
Some things are really beautiful!
But nothing lasts forever!
HOW CAN WE REPAIR THESE C&B FAILURES?
Seriousness of the problem1. Leave it alone if not causing any serious harm
2. Adjusting or repairing the fault
3. Replace the crown or bridge
fit checker
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.
Metal margins1. 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
Repairs by restoring in situ……. Occlusal Repairs
1. Amalgam
2. gold inlay
3. composite material
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
Repairs to porcelain Ceramic restorations
Composite
Separate silane coupling agent
Limited to sites with minimal occlusal forces.
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
Removing c&b’s1. Vibration of
ultrasonic scaler.
2. Good leverage at margins
3. A slide hammer Bridge remover
4. Crown can be cut off
Removing post & cores Using extraction forceps and using sharp twists –
carefully…
Files
Ultrasonic
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.
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 !
Cutting
How to cut a pfm
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.
Inhibited or Slow SettingVisual 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
Inhibited orSlow Setting
CAUSE SOLUTION
For Vinyl PolysiloxaneMaterials
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.
Inhibited or Slow SettingCAUSE 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.
Expired impression material
Inadequate mix.
Lack of Impression Detail
Visual Appearance: Muted detail reproduction.
Result: Crowns may be too tight, or loose, and not fit correctly.
Lack of Impression Detail
CAUSE SOLUTION
Impression material stored at
elevated temperature.
Store impression material at room temperature.
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.
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.
Lack of Impression Detail
CAUSE SOLUTION
Inadequate retraction of sulcus around prep.
Use good retraction technique, with proper
moisture control.
Lack of Impression Detail
CAUSE SOLUTION
Exceeding the working time. Follow manufacturer’s working
time specifications.
Choose material with longer working time.
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.
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.
Voids on the MarginCAUSE SOLUTION
Improper syringe technique. Keep syringe tip immersed in wash material to
avoid entrapping air.
Wiggle and stir while syringing. Push
material forward.
Voids on the MarginCAUSE SOLUTION
Inadequate coverage of marginal area with light body impression material.
Use wash material liberally on preparation
and abutments.
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 MarginCAUSE SOLUTION
Tray not seated straight. Insert impression tray straight.
Tearing at the Margin Visual Appearance:
Rip, or visible tearing on the margin of the preparation.
Result: Short crown margins and/or open margins.
Tearing at the MarginCAUSE SOLUTION
Check expiration date of impression material.
Ensure mixing instructions are followed and materials have a streak-free appearance.
Expired impression material.
Inadequate mix.
Tearing at the MarginCAUSE SOLUTION
Displace tissue to allow the impression material to access prepared area.
Consider two-cord retraction. Leave pilot cord in the sulcuswhen taking the impression.
Use impression material with sufficient tear resistance.
Insufficient retraction.
Tearing at the MarginCAUSE 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.
Facial-Lingual Pulls Visual Appearance: V-
shaped void, trough-like.
Result: Failure to capture complete and accurate dentition.
Facial-Lingual PullsCAUSE SOLUTION
Follow manufacturer’s working time specifications.
Choose material with longer working time.
Exceeding the working time.
Facial-Lingual PullsCAUSE SOLUTION
Do not move tray after seating.
Tray movement or repositioning
after seating.
Facial-Lingual PullsCAUSE SOLUTION
Use more material to create back flow effect.
Insufficient amount of impression
material used.
Facial-Lingual PullsCAUSE SOLUTION
Use lingual stops.
Use an impression tray that supports the flow
of the material.
Impression tray does not support flow of
impression material.
Tray-Tooth Contact Result: Restoration
may have slight distortion at marginal area, or rocks.
Visual Appearance: Show-through of tray. Impression tray exposed.
Tray-Tooth ContactCAUSE SOLUTION
Use proper size tray.
Test various tray sizes to ensure proper size.
Prepared teeth contact the sides or bottom
of impression tray.
Tray-Tooth ContactCAUSE SOLUTION
Carve out tray material properly before
applying wash.
Tooth contact with the pre-set tray material
when using the two-step technique.
Tray-Tooth ContactCAUSE SOLUTION
Fill tray adequately. Insufficient impression material used.
Delamination Visual Appearance:
Heavy body and light body materials not blended, or mixed together.
Result: Restoration will not seat or fit properly.
DelaminationCAUSE 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.
DelaminationCAUSE SOLUTION
Avoid contact with sulfur contaminants: Wear gloves proven not to
contain traces of sulfur.
Avoid contact with acrylic and methacryliccontaminants: Ensure impression
materialdoes not come into contact with methacrylateresidue from acrylatetemporary materials.
Sulfur or acrylic contamination of pre-set heavy body material in two-step technique.
Poor Bond of ImpressionMaterial 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.
No tray adhesive used. Use tray adhesive.
Poor Bond of ImpressionMaterial to the Tray
CAUSE SOLUTION
Incompatible tray adhesive used.
Use appropriate tray adhesive.
VPS adhesive for VPS.
Polyether adhesive for polyether materials.
Poor Bond of ImpressionMaterial to the Tray
CAUSE SOLUTION
Inadequate drying time for tray adhesive..
Follow manufacturer’s instructions for application, and drying time
Poor Bond of ImpressionMaterial to the Tray
CAUSE SOLUTION
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 ImpressionMaterial to the Tray
CAUSE SOLUTION
Stone ModelDiscrepancies 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
CAUSE SOLUTION
Stone ModelDiscrepancies
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 ModelDiscrepancies
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 ModelDiscrepancies
VPS
Hydrogen gas emission.
Follow manufacturer’s instruction for casting time.
CAUSE SOLUTION
Stone ModelDiscrepancies