Success and failure andproblem solving in prosthodontics complact final
Scenario Impression Framework check
SUCCESS ANDFAILUREProblem solving in fix prosthodontics
INTRO……. 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. Recent large surveys of bridges made in practice and elsewhere in different countries show that about 90% of bridges last at least 10 yrs.(Smith, 2000)
Inhibited or Slow Setting Visual Appearance: Result: Shiny, no detail Inadequate surface detail on cast Poor fitting restorations.
Inhibited or Slow SettingCAUSE SOLUTION For Vinyl Wear gloves proven Polysiloxane not to contain traces Materials of sulfur. Sulfur inhibition due If contamination is to contact of latex suspected, scrub gloves with affected area with tissue/tooth/retraction diluted hydrogen material or impression peroxide. material.
Inhibited or Slow SettingCAUSE SOLUTION Do not use impressions Residues from already used to fabricate custom temporary or the temporary restoration. Fabricate the temporary provisional cements crown or bridge after final (acrylics) present. impression has been made. Remove air-inhibited layer on the exposed surface with an alcohol wipe before making final impression.
Inadequate mix ResultVisual AppearanceNon-homogeneous mix. Slow setting impression material. Use mix tip according to manufacturer’s instruction for use. When using hand-mix materials ensure correct mixing ratio and thorough mix of catalyst and base paste.
Lack of Impression Detail Result: Crowns may be tooVisual Appearance: Muted tight, or loose, and not fitdetail reproduction. correctly.
Lack of Impression DetailCAUSE SOLUTION Impression material Store impression stored at material at roomelevated temperature. temperature.
Lack of Impression DetailCAUSE SOLUTION Impression material Keep impression stored at too low a temperature material at a prolongs the setting temperature of reactions 18°C/64°F at least changes viscosity and one day prior use. requires exceptionally high extrusion forces for automix materials
Lack of Impression DetailCAUSE SOLUTION Thick blood/saliva Remove blood and pooled around prep. saliva prior to making impression. Use 2-step impression technique.
Lack of Impression DetailCAUSE SOLUTION Inadequate Use good retraction retraction of sulcus technique around prep. proper moisture control.
Lack of Impression DetailCAUSE SOLUTION Exceeding the Follow working time. manufacturer’s working time specifications. Choose material with longer working time.
Lack of Impression DetailCAUSE SOLUTION Inadequate Use water based disinfection effects disinfectants surface quality according to (detail reproduction) FDA guidelines. and Follow dimensional stability. manufacturer’s instructions for use.
Voids on the Margin Visual Result: Appearance: The fit and Voids/holes on function of the margin of the final restoration prepared teeth. may be Incomplete margin. compromised. Short crown margins and/or open margins.
Voids on the MarginCAUSE SOLUTION Improper syringe Keep syringe tip technique. immersed in wash material to avoid entrapping air. Wiggle and stir while syringing. Push material forward.
Voids on the MarginCAUSE SOLUTION Inadequate Use wash material coverage of liberally on marginal area with preparation light body and abutments. impression material.
Voids on the MarginCAUSE SOLUTION Use good moisture control Blood and saliva technique. contamination Rinse and dry prep area before taking the impression. around prep. 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.
Tearing at the Margin Visual Result: Short Appearance: Rip, crown margins or visible tearing and/or open on the margin of margins. the preparation.
Tearing at the MarginCAUSE SOLUTION Expired impression Check expiration date material. of impression material. Ensure mixing Inadequate mix. instructions are followed and materials have a streak-free appearance.
Tearing at the MarginCAUSE SOLUTION Insufficient Displace tissue to allow the impression material retraction. 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.
Tearing at the MarginCAUSE SOLUTION Do not use impressions Residues from already used to fabricate custom temporary or the temporary restoration. Fabricate the temporary provisional cements crown or bridge after final (acrylics) present. impression has been made. Remove air-inhibited layer on the exposed surface with an alcohol wipe before making final impression.
Facial-Lingual Pulls Visual Result: Failure to Appearance: V- capture complete shaped void, and accurate trough-like. dentition.
Facial-Lingual PullsCAUSE SOLUTION Exceeding the Follow working time. manufacturer’s working time specifications. Choose material with longer working time.
Facial-Lingual PullsCAUSE SOLUTION Tray movement or Do not move tray repositioning after seating. after seating.
Facial-Lingual PullsCAUSE SOLUTION Insufficient amount Use more material of impression to create back flow material used. effect.
Facial-Lingual PullsCAUSE SOLUTION Impression tray Use lingual stops. does not support Use an impression flow of impression tray that supports material. the flow of the material.
Tray-Tooth Contact Result: Visual Restoration may Appearance: have slight Show-through of distortion at tray. Impression marginal area, or tray exposed. rocks.
Tray-Tooth ContactCAUSE SOLUTION Prepared teeth Use proper size tray. contact the sides or Test various tray bottom of sizes to ensure impression tray. proper size.
Tray-Tooth ContactCAUSE SOLUTION Tooth contact with Carve out tray the pre-set tray material properly material when using before applying the two-step wash. technique.
Tray-Tooth ContactCAUSE SOLUTION Insufficient Fill tray adequately. impression material used.
Delamination Visual Result: Appearance: Restoration will Heavy body and not seat or fit light body properly. materials not blended, or mixed together.
DelaminationCAUSE SOLUTION Exceeding the working Follow manufacturer’s time. working time specifications. Choose material with longer working time. Impression material Store impression stored at elevated temperature. material at room temperature.
DelaminationCAUSE SOLUTION Avoid contact with sulfur Sulfur or acrylic contaminants: contamination of Wear gloves proven not to contain traces of sulfur. pre-set heavy body Avoid contact with acrylic material in two-step and methacrylic contaminants: technique. Ensure impression materialdoes not come into contact with methacrylate residue from acrylate temporary materials.
Poor Bond of ImpressionMaterial to the Tray Visual Result: Crown(s) Appearance: may be tight and Impression pulling not seat fully, or away from the require excessive sides/bottom of internal tray. adjustment.
Poor Bond of ImpressionMaterial to the TrayCAUSE SOLUTION No tray adhesive Use tray adhesive. used.
Poor Bond of ImpressionMaterial to the TrayCAUSE SOLUTION Incompatible tray Use appropriate tray adhesive used. adhesive. VPS adhesive for VPS. Polyether adhesive for polyether materials.
Poor Bond of ImpressionMaterial to the TrayCAUSE SOLUTION Inadequate drying Follow time for tray manufacturer’s adhesive.. instructions for application, and drying time
Poor Bond of ImpressionMaterial to the TrayCAUSE SOLUTION Thin plastic trays Use a tray that fits allow deflection, better, and is stiffer which can cause and more rigid. rebound upon removal.
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
Stone ModelDiscrepanciesCAUSE SOLUTION Tooth contact with Instruct patient to impression tray bite passively in gauze of double bite centric occlusion tray when using dual causes water to arch trays. leach out of the tray, Fill tray with dehydrating the sufficient amount of stone. material.
Stone ModelDiscrepancies CAUSE SOLUTION Cast not made Provide as much according to model information as preparation possible to the lab. Indicatetype of guidelines and lacks impression material detail. (polyether or VPS) and whether or not the impression has been disinfected. VPS Follow manufacturer’s Hydrogen gas emission. instruction for casting time.
WHY C&B WORKS FAIL? MECANICAL FAILURE CHANGES IN ABUTMENT TOOTH DESIGN FAILURES INADEQUATE CLINICAL OR LAB TECHNIQUE
MechanicalFailures…. Porcelain/PJC # Failure of solder joints Distortion Occlusal/Incisal wear & perforation Lost facings
Porcelain # Stresses are developed within PJC’s as a result of contraction on cooling after the firing cycle. These stresses produce minute cracks, some of which originate at the fit surface & propagate to produce failure if the crown is subjected to sufficient force. These stresses are concentrated around sharp internal angles of the fit surface, so the external angles of PJC preps should be rounded to reduce them.
Porcelain # Distortion of metal-ceramic framework invariably results in the loss of porcelain Inadequate metal support Excessive porcelain thickness Technical flaws Normal function (occlusal forces) Trauma
Failure of solder joints 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.
CHANGES IN ABUTMENT TOOTH…. Progression of perio disease Abutment tooth may become non-vital (pulpal problems) Recurrent caries occurring at margins of retainers: change in diet. lapsed oral hygiene. inadequate restoration design
Distortion 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.
Occlusal/Incisal Wear &Perforation 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
Marginal deficiencies 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.
Casting difficulties “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.
Casting difficulties 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.
REPAIRMENT TIME… Some things are really beautiful! But nothing lasts forever! HOW CAN WE REPAIR THESE C&B FAILURES?
TECHNIQUES FOR ADJUSTMENTS,ADAPTATIONS AND REPAIRS TO CROWNSAND BRIDGES Assessing the seriousness of the problem Leave it alone if not causing any serious harm Adjusting or repairing the fault Replace the crown or bridge
Adjustments by grinding andpolishing in situ 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.
In case of metal margins 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.
Repairs by restoring insitu……. 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.
Repairs at the Margins 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.
Repairs to Porcelain 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.
C&B – METABOND WITHCOMPOSITE TO REPAIRPORCELAIN…..
3.Ceramic facings 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.
4.‘Unit construction’ bridgefacings Before the routine use of metal ceramic materials, bridges were often made with Separate PJC’s cemented to it. However, they often broke as they were usually reduced approximally for connector accomodation Patients sometimes were given a spare set when bridge was cemented
Removing and/or replacing entiresections of a bridge A good purpose for removable, telescopic crown retained bridges and of dividing multiple unit bridges into smaller sections. When a part of a bridge is removed, the remainder can be modified like cutting a slot for a movable joint and replacing the lost section. Bridges can also be extended using same principles if more teeth are apparently lost
Removing C&B’s 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.
Removing Crowns 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.
Removing Post & Cores Using extraction forceps and using sharp twists – carefully… Several other devices can be used
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 – CeramicCrowns 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 !
Removing Bridges(3 situations) 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 Cont….. 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.
Removing Bridges intact All metal bridges and minimal preparation bridges are slightly more flexible and can be removed more easier than metal ceramic conventional bridges. Slide hammers can fit under margins, under pontics and embrasure spaces, even in drilled holes on palatal surfaces of retainers or pontics.
Other Techniques….. Ultrasonic vibration with a scaler can loosen crowns and bridges. Loops of soft wire and sliding hammer If no slide hammer, than heavy duty instruments like mallet is passed through the loops well outside the mouth and sharp blows are applied. – need to warn patient beforehand ( rather dramatic approach)
Practical Points A large proportion of failures are partial, a level of acceptability must be reached by dentist and patient (esp min prep bridges) Periodontally affected teeth can frequently be treated. Never should be used to cover up poor design Bridge can be made with fail safe procedures