Impression techniques in fpd
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This presentation gives an overview of the impression techniques used in fixed partial dentures
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Impression techniques in fpd
- 2. Introduction History Requirements of an impression Pre-requisistes Impression materials Impression trays Techniques Disinfection Conclusion
- 3. An impression is a negative likeness of the teeth and the surrounding structures A fixed prosthesis cannot be fabricated without a proper impression A positive likeness of the impression has to be obtained
- 4. 1756 1955 1945 1937 1857 1853 1820 First described making impression with softened wax Introduced metal impression tray First used Plaster of Paris for making impression Phillip Pffaf Chapin Harris Christophe Francois Delabarre Charles Stent Sears First used agar for recording impressions of crows First introduced impression compound Alginate was introduced in the US during the WW II Developed synthetic rubber based impression materials S L Pearson
- 5. Adjacent structures Unprepared teeth should be recorded to facilitate articulation Exact duplicate Should include the prepared surface and the uncut surfaces Attention to anterior teeth Influences anterior guidance which determines the occlusal surface of the teeth Free of voids Imperfections produce inadequacies
- 6. Moisture control saliva and blood Gingival tissues must be displaced laterally to allow access and to provide space for the material
- 7. Tissue health Saliva control Gingiva displacement Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 8. Careful evaluation of surrounding tissues Minimal tissue damage Properly adapted well contoured restoration vital for sustaining periodontal health Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 9. Supra-gingival margins rubber dam Absorbent cotton and saliva evacuators Moisture absorbing cards Local anaesthesia Anti sialogogues Given 30-60 minutes before drying effect is required Brand name Active ingredient Dosage Pro-banthine Propantheline bromide 7.5-15 mg Robinul Glycopyrrolate 1-2 mg Sal-tropine Atropine sulfate 0.4 mg Antipas, Bentyle Dicyclomine 10-20 mg Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 10. To obtain adequate access to prepared tooth Mechanical Chemical surgical Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 11. Mechanical displacement Placement of cord non impregnated or impregnated Pushed into the sulcus mechanically stretches the circumferential PDL Larger sizes of cords to be avoided “double up” and become traumatic Impregnated cords give better gingival displacement Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 12. Step – by – step procedure Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 13. Hemorragecontrolwith aninfusorsyringe Fill syringe with ferric sulfate and attach infusor tip Rub the tip back and forth for approximately 30 seconds Irrigate and gently dry the tissues InspectRepeat Moisten the cord before removing Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 14. Displacement paste •Alternative to cord •Contains AlCl3 paste is injected into dry sulcus •Good hemostasis with better comfort •Less tissue displacement makes die trimming difficult Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 15. Electrosurgery •Minor tissue removal •Inner epithelial lining of the gingival sulcus is removed •Potential for post surgical recession Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 16. Soft tissue laser • Means of removing controlled amounts of tissue before impression making Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 17. Reversible hydrocolloid Polysulfide polymer Condensation silicone Polyether Addition silicone Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 18. Material Advantages Disadvantages Recommended uses Precautions Irreversible hyfrocolloid Rapid set Straightforward technique Low cost Poor accuracy and surface accuracy Diagnostic casts Not suitable for definitive casts Pour immediately Reversible hydrocolloid Hydrophilic Long working time Low material cost No custom tray required Low tear resistance Low stability Equipments needed Multiple preparations Problems with moisture Pour immediately Use only with stone Polysulfide High tear strength Easier to pour than other elastomers Messy Unpleasant odour Long setting time Stability only fair Most impression Pour within 1 hr Allow 10 minutes to set Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 19. Materials Advantages Disadvantages Recommneded uses Precautions Condensation silicone Pleasant to use Short setting time Hydrophobic Poor wettability Low stability Most impressions Pour immediately Care to avoid voids Addition silicone Dimensional stability Pleasant to use Short setting time Automix available Hydrophobic Poor wetting Release H2 Hydrophilic formulations imbibe moisture Most impressions Delay pour of some materials Care to avoid air bubbles Polyether Dimensional stability Accuracy Short setting time Automix available Set material very stiff Imbibition Short working time Most impressions Care not to break teeth while separating Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 20. Wettability Viscosity cost How to make the decision? ?? Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 21. Wettability Hydrophilic Eg: alginate, agar, polyether Hydrophobic Eg: polysufide, polyvinyl siloxane, condensation silicone Greater the contact angle, Greater the chance of air entrapment McCormick JT, Antony SJ, Dial ML, Duncanson Jr MG, Shillingburg Jr HT. Wettability of elastomeric impression materials: effect of selected surfactants. International Journal of Prosthodontics. 1989 Sep 1;2(5).
- 22. “Shear thinning” Most viscous – heavy bodied polysulfide Least viscous – light bodied polysulfide and condensation silicone Viscosity increases after start of mixing
- 23. Polysulfide impression material with custom tray were found to be least expensive Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 24. Custom trays Stock trays Retention: Perforation, rim locks, adhesives Customtray: Autopolymerising Photopolymerising Thermoplastic Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 25. Improves accuracy limiting volume of material Reduces stressing during removal and thermal contraction Tray rigidity is important Resin thickness of 2-3 mm Clearance of 2-3mm Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 26. 01 02 03 04 05 Mark the border of the tray 5 mm apical to the crest of the free gingival margin Create stops on the non functional cusps to maintain even space (45 degrees) Mix resin and set aside till doughy adapt resin to cast Make a handle from the excess Trim and finish with acrylic bur Adapt a wax spacer (2 layers) 2.5 mm thickness Soften wax , adapt with light pressure Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 28. 01 02 03 04 05 Remove the photopolymerized tray from the light proof packaging Shape and attach a handle by moulding excess material Position in curing unit for 2 minutes and separate the tray from the cast. Paint with air barrier coating Clean under running water Carefully adapt the sheet in three pieces. Small pieces in the areas of the stops first
- 31. Rigid Consistent thickness of 2-3 mm Extend 3-5 mm cervical to the gingival margins Shaped to allow muscle attachments Stable on the cast with stops No sharp edges Fabricated 9 hours before use to avid distortion
- 32. Isolate the prepared tooth, place the retraction cord. Place tray from storage bath to tempering bath for 10 mins Retraction cord is removed after wetting the surface gently Using a blunt syringe, inject material onto the prepared surface Make the sectional impression with the hose connected to the tray While the sectional impression is being made, the full arch tray must be loaded and tempered Sulcular retraction need not be repeated. Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 33. Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 34. Armamentarium •Polysulfide impression kit (regular base and •accelerator) •Polysulfide impression kit (light base and accelerator) •Adhesive (butyl rubber cement) •Two disposable mixing pads •Two stiff spatulas •Syringe with disposable tip •Two 2 x 2-inch gauze sponges •Alcohol •Custom resin tray Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 35. Try the custom tray in the patient’s mouth Insert the retraction cord Squeeze out 1.5 inch of base paste and accelerator on a mixing pad Collect the accelerator on a spatula and incorporate into the white base paste mix back and forth. Fold a sheet of the mixing pad into a cone and wipe the material on the spatula. Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 36. Squeeze into the syringe Inject material into the sulcus after removing the cord Seat the tray slowly til the stops hold the tray in one position held in position for 8-10 minutes Blow dry and inspect Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 37. Armamentarium •Silicone impression kit (putty, base, and accelerator) •Tray adhesive—poly(dimethyl) siloxane and ethyl silicate •Measuring scoop •Disposable mixing pad •Stiff spatula •Syringe with disposable tip •2 x 2-inch gauze sponges •Stock trays (rim-lock or perforated) •Laboratory knife with no. 25 blade Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 38. Select a stock tray Apply a thin coat of adhesive and allow to dry Take 2 scoops of base on a mixing pad (one for a sectional tray) Add six drops of accelerator for each scoop Spatulate on a mixing pad first and then knead for 30sec Roll into a cigar shape and place on the tray selected Cover the base with a polyethyle ne sheet Remove the impression and set aside Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 39. Prepare the tooth under LA and place the retraction cord Squeeze out 8 inches of thin silicone base onto a mixing pad (4 inches for sectional) Add one drop pf accelerator per inch mix for 30 sec Dry the preparation Remove the cord carefully without causing hemorrage Seat the tray firmly without any downward pressure for 6 mins Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 40. Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 41. Armamentarium •Dispenser •Cartridge (base and accelerator) •Mixing tip •Disposable mixing pad •Syringe with disposable tip •2 x 2-inch gauze sponges •Custom impression tray •Tray adhesive
- 42. Paint custom tray with adhesive 15 minutes before impression is made Spatulate light-body for 45 secs and load into syringe Remove the retraction cord carefully Inject the impression material Exchange the syringe for a loaded tray and firmly seat it in place for 7 minutes Quickly remove and evaluate Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 43. Armamentarium •Impression kit (base and ace •Tray adhesive •Disposable mixing pad •Stiff spatula •Syringe with disposable tip •2 x 2-inch gauze sponges •Custom resin tray Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 44. Coat the custom tray with adhesive and allow to dry Express 7.5 inches of base and accelerator onto a mixing pad Mix for 1 m in till streaks are removed Load the syringe Remove the retraction ocrd carefully Seat the loaded tray in place for about 4 mins Rise it, blow dry and evaluate Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, Kessler JC. Fundamentals of fixed prosthodontics. Quintessence Publishing Company; 2012.
- 45. Evaluate the custom tray Apply tray adhesive and allow to dry Isolate the abutment teeth and place gingival retraction ocrd Blend the two paste thoroughly – mix for 10s Load the syringe Remove the displacement cord and place the tip of the syringe along the margins and inject Seat the loaded tray and let it remain for 6-12 min Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 46. Same steps as in double mix technique Only one mix is used to load the syringe Higher viscosity mix with shorter working time Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 47. Material in pre-packed cartridges with disposable mixing tip The homogenously mixed material can be directly placed onto the tooth Eliminates hand mixing and fewer voids Not available for polysulfide Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 48. Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 49. Dual arch/ triple tray Select and evaluate a tray Apply adhesive Remove cord and apply impression material onto critical areas Place the loaded closed mouth tray into position and have the patient close properly Remove and evaluate Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
- 50. Disinfection Irreversible hydrocolloid Reversible hydrocolloid Polysulfide Silicones Polyethers 2% Gluteraldehyde (10 min soak) N/A N/A Yes Yes Yes Iodophors(1:213dil ution) Yes Yes Yes Yes Yes Chlorine compounds Yes Yes Yes Yes Yes Complex phenols N/A Limited data Yes Yes Yes Phenolic gluteraldehydes N/A Yes Yes Yes yes Rosenstiel SF, Land MF, Fujimoto J. Contemporary Fixed Prosthodontics-E-Book. Elsevier Health Sciences; 2015 Jul 28.
Editor's Notes
- Except for polyether, all impression materials are hydrophobic more chances for voids
- Subginigval margins sulcular damage is inevitable transient, provided provisional restoration is proper
- Impregnated cord astringent shrinks gingival tissue transient ischemia closes quickly immediate impression Aluminium chloride and ferric sulfate cause minimal tissue damage o Contact between astringent solution and prepared tooth must be minimized if smear layer is to be maintained. o Mono acidic hemostatic agent epinephrine (C/I – cardiac patients may cause tachycardia)
- Evaluate?? Should be able to see the preparation margin clearly and the cord uninterrupted without any soft tissue folding over it. It should remain directly accessible over a minute Repeated use of the gingival retraction cord must be avoided as it may cause recession. Sometimes the use of a double cord technique is useful. For this to be successful, there should be atleast 1mm of space between the top of the initial cord and the preparation margin.
- Hollow metal tip contains a cotton filament to help control flow of the medicament
- Caution to be exercised while pouring impression made of materials whose surface is more difficult to wet
- Shear thinning when a monophasic body is suspended over a false body (material of thicker consistency) can stay without sagging or dripping. At the sae time, it exhibits sufficient viscosity when expressed through a syringe thixotropic material
- Not primary criteria for choosing impression material
- For reversible hydrocolloids, reducing bulk may not increase accuracy, instead it is the reverse.
- Alternatively, the resin maybe soaked in boiling water for 5 mins and allowed to cool to room temperature
- Packaged as semi-solid gel in polyethylene tubes. Requires 3 water baths. Liquifying bath, storage bath tempering bath.
- Pressure exerted on the tray while the wash is polymerizing will produce stresses in the semi-rigid putty lining the impression tray. When the impression is removed from the mouth, the stresses will relax, resulting in deformation and distortion of the impression
- Decreased setting time swift and prganised