Impressions for fpd / implant dentistry course

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Impressions for fpd / implant dentistry course

  1. 1. IMPRESSIONS IN FIXEDPARTIAL DENTURES INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. INTRODUCTION www.indiandentalacademy.com
  3. 3.  To obtain an impression is the first step necessary for the indirect fabrication of a prosthesis.  An impression is an imprint or negative likeness of teeth and tissues.  Fixed prosthodontics is practiced as indirect restorations. www.indiandentalacademy.com
  4. 4.  Well-fitting indirect restorations can only be made if there are accurate casts of the oral tissues available, made from high quality impressions.  A good quality impression is only obtained when we have a thorough knowledge of materials, their properties, and techniques for their best manipulation. www.indiandentalacademy.com
  5. 5. TERMINOLOGIES www.indiandentalacademy.com
  6. 6. IMPRESSION : A negative likeliness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry – G.P.T-8 IMPRESSION TRAY : A receptacle into which suitable impression material is placed to make a negative likeliness (or) a device that is used to carry, confine, and control impression material while making impression– G.P.T-8 www.indiandentalacademy.com
  7. 7. IMPRESSION MATERIAL: Any substance or combination of substances used for making an impression or negative reproduction. – G.P.T- 8 IMPRESSION TECHNIQUE : A method and manner used in making a negative likeness. – G.P.T-8 www.indiandentalacademy.com
  8. 8. HistoryHistory  Philip Pfaff-1756  First described taking impression with softened wax  Christopher Francois Delabarre-1820  Introduced the metal impression tray  Chapin Haris-1853  First used Plaster of Paris for making impressions  Charles Stent-1857  Introduced the first impression compound www.indiandentalacademy.com
  9. 9.  Sears-1937  First used agar hydrocolloids for recording crown impressions.  United States-1945  Introduced alginate during World War II.  SL Pearson-1955  Developed synthetic rubber base impression materials  Polysulfide- Late 1950’S  First developed as an industrial sealant. www.indiandentalacademy.com
  10. 10.  Condensation Silicone- Early 1960’s  Addition Silicone-1970’s  Polyether- Late 1970’s  Polyether Urethane Dimethacrylate - Late 1980’s www.indiandentalacademy.com
  11. 11. Properties Of An Ideal Impression 1)Complete plasticity before cure 2)Sufficient fluidity to record fine detail. 3)The ability to wet the oral tissues. 4) Dimensional accuracy. 5)Dimensional stability. 6)Complete elasticity after cure. 7)Optimal stiffness. www.indiandentalacademy.com
  12. 12. Impression Materials Used In F.P.D 1)Hydrocolloid impression material a) Reversible hydrocolloid b) Irreversible hydrocolloid 2)Elastomeric impression materials a) Polysulfide b)Addition silicone c) Condensation silicone d)Polyether Dimethacrylate www.indiandentalacademy.com
  13. 13. AGAR (reversible hydrocolloid) History  In 1925, Alphous Poller of Vienna was granted a British patent for a totally different type of impression material.  Later Poller's 'Negacoll’ was modified and introduced to the dental profession as 'Dentacol’ in 1928. www.indiandentalacademy.com
  14. 14. Example  Slate Hydrocolloid (Van R)  Cohere  Superbody  Super syringe www.indiandentalacademy.com
  15. 15.  Available as - syringe and tray material Composition: Component Function Composition Agar Brush – heap structure 13 – 17% Borax Strength 0.2 – 0.5% Potassium Sulfate Gypsum hardener 1.0 – 2.0% Water Reaction 80% Alkyl Benzoate Prevent growth of mold in impression material during storage. 0.1% Color and Flavors Taste & appearance Trace www.indiandentalacademy.com
  16. 16.  Setting reaction: Agar hydrocolloid (hot) Agar hydrocolloid (cold) (Sol) (Gel) Cool to 43 C Heat to 100 C Manipulation: Three chamber conditioning unit (1) Liquefy at 100 0 C for 10 minutes converts gel to sol (2) Store at 65 – 68 0 C place in tray (3) Temper at 46 0 C for 3 minutes seat tray (4) cool with water at 20 0 C for 3 minutes converts sol to gel www.indiandentalacademy.com
  17. 17. Advantages  Accurate reproduction of surface detail  Hydrophilic  displace moisture, blood, fluids  Inexpensive  No custom tray or adhesives  Pleasant  No mixing required www.indiandentalacademy.com
  18. 18. Disadvantages  Initial expense  special equipment  Material prepared in advance  Tears easily  Dimensionally unstable  immediate pour  single cast  Difficult to disinfect www.indiandentalacademy.com
  19. 19. ALGINATE (irreversible hydrocolloid)  Alginate was developed as a substitute for agar when the agar impression material became scarce because of World war II (Japan was a prime source of agar). Examples  Jeltrate (Dentsply/Caulk)  Coe Alginate (GC America)  Integra  Superjel  Tropicalgin  Xantalgin www.indiandentalacademy.com
  20. 20. Composition Component Function Weight percentage Na / Potassium alginate Soluble alginate 15 Calcium sulfate dihydrate Reactor 16 Potassium titanium Fluoride Accelerator 3 Zinc oxide Filler particles 4 Diatomaceous earth Filler particles 60 Sodium phosphate Retarder 2 www.indiandentalacademy.com
  21. 21. Modified alginates  Alginate in the form of sol - containing the water but no source of calcium ions - a reactor of Plaster of Paris  Alginates modified by the incorporation of silicone polymers (paste form)  Dustless alginate - glycerin incorporated to agglomerate the particles.  Making the powder denser so that no dust is formed when the lid is opened after tumbling. www.indiandentalacademy.com
  22. 22. Setting reaction: (gelation process) 2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4 Na alginate + CaSO4 Ca alginate + Na2SO4 (powder) (gel) H2O www.indiandentalacademy.com
  23. 23. NEWER ALGINATES  Kromopan 100. manufactured by LASCOD  MILLENIUM ALGIN is considered an alginate of new generation alginate.  The impression can be stored for many hours in a Long Life Bag before casting the model without undergoing any change for over 100 hours www.indiandentalacademy.com
  24. 24. AUTOMIX DISPENSING: (Alginate from Kerr international)  No hand mixing. Eliminates mess and cleanup. Saves time and material.  Delivery options. Cartridge or Volume™ auto mix dispensing.  Impressions remain stable. You can pour immediately or when it’s convenient. Impressions retain dimensional stability for months. www.indiandentalacademy.com
  25. 25. Manipulation  W/P ratio as specified by the manufacturer.  Mixing is done in a clean flexible plastic bowl with a clean wide bladed, reasonably stiff metal spatula.  The mixing is started with a stirring motion to wet the powder with water.  Once the powder has been moistened, rapid spatulation by swiping or stropping against the side of the bowl is done.  A vigorous figure-eight motion can also be used www.indiandentalacademy.com
  26. 26. Mechanical mixing devices www.indiandentalacademy.com
  27. 27. Advantages:  Inexpensive  Easy to use  Hydrophilic  displace moisture, blood, fluids  Stock trays www.indiandentalacademy.com
  28. 28. Disadvantages:  Tears easily  Dimensionally unstable  immediate pour  single cast  Lower detail reproduction  unacceptable for working cast of fixed prosthodontics  High permanent deformation  Difficult to disinfect www.indiandentalacademy.com
  29. 29. NON AQUEOUS ELASTOMERIC IMPRESSION MATERIALS  These are Synthetic rubbers.  These mimic natural rubber (scarce during World War II)  Initially called rubber impression materials  Currently referred as elastomers or elastomeric impression materials. www.indiandentalacademy.com
  30. 30. www.indiandentalacademy.com
  31. 31. Polysulfide  The first elastomer used for dental impressions Examples  Permlastic (Kerr)  Omni-Flex (GC America) – copper hydroxide system.  Coe-flex (GC-Amer)  Neo-plex (Miles) www.indiandentalacademy.com
  32. 32.  Available in 3 viscosities,  light body and medium body heavy body. www.indiandentalacademy.com
  33. 33. Setting reaction: www.indiandentalacademy.com
  34. 34. Manipulation  With the proper lengths of the two pastes squeezed onto a mixing pad or glass slab, the catalyst paste is first collected on a stainless steel spatula and then distributed over the base, and the mixture is spread out over the mixing pad.  The mass is then scraped up with the spatula blade and again smoothed out. www.indiandentalacademy.com
  35. 35.  If sufficient force is applied and spatulation is performed rapidly, the material will seem thinner and easier to handle. This phenomenon is known as pseudoplasticity.  Most accurate impressions are made using custom acrylic trays because of uniform thickness of the material. www.indiandentalacademy.com
  36. 36. Advantages Disadvantages  Long working time  Proven accuracy  High tear resistance  Less hydrophobic  inexpensive to use  Long shelf life Requires a custom tray Must be poured in stone immediately Potential for significant distortion Odor offends patients Messy and stains clothes Second pour is less accurate www.indiandentalacademy.com
  37. 37. SILICONES www.indiandentalacademy.com
  38. 38. CONDENSATION SILICONE  Condensation reaction – a polymerization reaction in which the polymer chains all grow simultaneously and a reaction byproduct is formed. Available In Three Viscosities:  Light body  Medium body  Putty body Supplied as:  Paste – two pastes in collapsible tubes  Putty – jars www.indiandentalacademy.com
  39. 39. Examples:  Speedex (Coltene/Whaledent)  Primasil (TISS Dental)  Accoe (GC-Amer)  Xantopren (Unitek)  Elasticon (Kerr)  Cuttersil (Miles) www.indiandentalacademy.com
  40. 40. Composition: Composition Components Function Base paste Hydroxyl terminated polydimethyl siloxane prepolymer undergoes cross linking to form rubber Silica Filler Reactor Orthoethyl Silicate Cross linking agent Stannous octate Catalyst www.indiandentalacademy.com
  41. 41. Setting reaction: www.indiandentalacademy.com
  42. 42. Advantages:  Better elastic properties  Clean, pleasant  Stock tray  putty-reline  Good working and setting time Disadvantages: Permanent deformation – high – 1-3% Poor dimensional stability high shrinkage polymerization Hydrophobic poor wettability www.indiandentalacademy.com
  43. 43. ADDITION SILICONES  Frequently called polyvinylsiloxane or vinyl polysiloxane impression materials. Supplied in 4 viscosities  Light body  Medium body  Heavy body  Putty www.indiandentalacademy.com
  44. 44. Examples:  Extrude (Kerr)  Express (3M/ESPE)  Aquasil (Dentsply Caulk)  Genie (Sultan Chemists)  Virtual (Ivoclar Vivadent) www.indiandentalacademy.com
  45. 45. Composition: Components Function Base paste Hydroxyl terminated polymethyl siloxane prepolymer Undergoes cross linking to form rubber Colloidal silica Filler Reactor Polyvinyl silicone prepolymer Colloidal silica Filler Chloroplatinic acid Catalyst www.indiandentalacademy.com
  46. 46. Advantages:  Excellent reproduction of surface details  Highly accurate  High dimensional stability  pour up to one week  Stock or custom trays  Multiple casts  Easy to mix  Pleasant odor Disadvantages:  Expensive  Short working time  Lower tear strength  Possible hydrogen gas release www.indiandentalacademy.com
  47. 47. POLYETHER  First material introduced for dental impressions.  Introduced in Germany in late 1960s. Available as  Base and accelerator in collapsible tubes.  The accelerator tube is usually smaller.  Earlier supplied in single viscosity.  A third tube containing a thinner was provided. Available in 3 viscosities  Light body  Medium body  Heavy body www.indiandentalacademy.com
  48. 48. Examples  Impregum F (3M/ESPE)  Permadyne (3M/ESPE)  Pentamix (3M/ESPE)  P2 (Heraeus Kulzer)  Polygel (Dentsply Caulk) www.indiandentalacademy.com
  49. 49. www.indiandentalacademy.com
  50. 50. SETTING REACTION: www.indiandentalacademy.com
  51. 51. Advantages  Highly accurate  Good dimensional stability  Least hydrophobic  Good surface detail  Pour within one week  Multiple casts  Good wettability  Good shelf life Disadvantages Expensive Short working time Rigid difficult to remove from undercuts Bitter taste Low tear strength Absorbs water - changes dimension - Leaches components www.indiandentalacademy.com
  52. 52. POLYETHER URETHANE DIMETHACRYLATE Composition:  - polyether urethane dimethacrylate resin.  - diketone initiator  - amine accelerator  - 40 – 60% silica filler (SILICON DIOXIDE) www.indiandentalacademy.com
  53. 53.  Clear tray (TRANSPARENT),  photo initiated by 400 – 500 nm blue light  Advantage - unlimited working time (CONTROLLED BY OPERATOR),  short setting time  Disadvantage - surface polymerization is inhibited by moisture. www.indiandentalacademy.com
  54. 54. Impression Techniques  1. Stock tray technique - Double mix - Single mix  2. Custom tray technique - Single mix  3. Closed bite double arch technique  4. Copper band technique  5. Reversible hydrocolloid technique www.indiandentalacademy.com
  55. 55. STOCK TRAY IMPRESSION TECHNIQUE (Putty wash technique): Mixing method: Double mix and single mix Procedure :  Place patient in supine position.  Operator is positioned at nine o clock and assistant is positioned at 3 o’clock position.  Select tray type based on relative need for retention and personal preference.  Select tray shape and size based on patients arch shape and size. www.indiandentalacademy.com
  56. 56.  Coat the tray with adhesive on the inside and rim.  Mix the high viscosity putty impression material according to manufacturer’s instructions.  Roll putty into elongated cylinder.  Insert into the stock impression tray. www.indiandentalacademy.com
  57. 57.  Cover putty with the manufacturer’s spacer (a sheet of polyethylene)  Insert and seat the tray with a rocking motion.  Hold and wait until initial set.  Remove from the mouth with minimal sideward movement.  Wait and test for final set with the clinical final set, which is when a finer nail impression rebounds completely.  Peel off the spacer.  Remove excess impression material with a sharp knife. www.indiandentalacademy.com
  58. 58. SINGLE MIX TECHNIQUE: MAKING FINAL IMPRESSION:  Choose a large mixing pad approximately six by eight inches.  Choose a spatula that is long enough to pick up the mixed impression material, yet sufficiently pliable to mix the material against the pad. www.indiandentalacademy.com
  59. 59.  Mix the low-viscosity, impression material according to manufacturer’s instructions.  First use a circular motion, joining the two strands. Then a figure eight motion to blend and flatten the mixture onto the mixing pad.  While flattening the mixture, limit the number of times of lifting the spatula from the pad, this reduces the number of voids in the mixture. www.indiandentalacademy.com
  60. 60.  Load the low viscosity impression material on to a syringe .  Syringe in the inaccessible area first eg disto lingual line angle.  Seat the tray .  Wait for the final set.  Remove the tray parallel to the preparation path of withdrawal.  The impression is evaluated for the finish lines and for any distortion and tear. www.indiandentalacademy.com
  61. 61. DOUBLE MIX TECHNIQUE:  For the stock tray double mix insert the low viscosity impression material into the tray without overfilling it.  Spread the cheeks one at a time, first with the tray and then with an index finger.  Position the tray over the arch.  Seat from posterior to anterior, allowing the excess to extrude anteriorly.  Apply force in a vertical direction until further seating is impossible.  Evaluate final position and adjust tray quickly if necessary. www.indiandentalacademy.com
  62. 62. EVALUATING FINAL IMPRESSION  Elastomeric material should be present 0.5 mm beyond visible finish line.  Note presence of bur marks, the junction of smooth root surface, and continuous finish line.  There should be no shiny smooth areas; if present, they suggest moisture contamination.  There should be no tray show- though in any areas of the impression except at tissue stops. www.indiandentalacademy.com
  63. 63.  There must be no voids present, they suggest mixing problems or contamination.  There should be no thin areas leaving the finish line unsupported. These areas distort under the weight of the stone. www.indiandentalacademy.com
  64. 64. Custom Tray Fabrication For Elastomeric Impression 1)Mark the border of the tray on the diagnostic cast with a pencil approximately 5mm apically to crest of the free gingiva. www.indiandentalacademy.com
  65. 65. 2)Adapt a wax spacer to the diagnostic cast two layers for 2.5mm thickness approximately. www.indiandentalacademy.com
  66. 66. Tray Stops www.indiandentalacademy.com
  67. 67. 3)Apply a layer of tinfoil over the wax. 4)Mix autopolymerizing acrylic resin according to manufacturers recommendation 5)Adapt the resin to the cast when in dough stage. www.indiandentalacademy.com
  68. 68. Tray handle is made Borders are trimmed and the tray is polished www.indiandentalacademy.com
  69. 69. Lateral wings can be made which will help in easy removal of the tray www.indiandentalacademy.com
  70. 70. Prepare syringe:  Lubricate the syringe lightly.  Trim tip. Open orifice to increase rate of flow or close orifice to decrease rate of flow.  Measure arch length of tray to guide in dispensing the amount of elastomer. (Dispense one time the length of the tray for the low viscosity elastomer). www.indiandentalacademy.com
  71. 71. Making the final impression. Medium or high viscosity is used in the tray and low viscosity in the syringe. The syringe is loaded with the low viscosity material and syringed in the prepared site. The high viscosity material is placed in the custom tray and seated in the mouth. www.indiandentalacademy.com
  72. 72. The impression is removed and evaluated. www.indiandentalacademy.com
  73. 73. Close Bite Double Arch Method synonyms :dual quad tray, double arch , triple arch , accu -bite ,closed mouth impression. Requirements The articulator should provide for a positive stop or there should be sufficient teeth to maintain the vertical dimension. There should be sufficient space distal to the terminal tooth in the arch to allow tray approximation. www.indiandentalacademy.com
  74. 74. Advantages The physical deformation of the mandible is minimal The shifting of teeth occurring during maximum intercuspation is captured. Less impression material is needed. Less gagging may occur. Disadvantages The tray is not rigid . Limited to one casting per quadrant . The distribution of impression material is not uniform www.indiandentalacademy.com
  75. 75. Technique Evaluate the fit of the tray in the patients mouth. Observe the complete bilateral closure and the patients comfort. Practice till the patient is familiar with the task. www.indiandentalacademy.com
  76. 76. Making the final impression  Mix the low viscosity material and load the syringe  The high viscosity material is used in the tray.  After the low viscosity material is syringed the tray is positioned on the arch.  Instruct the patient to close the mouth and observe for the interdigitation on the opposite arch.  Wait for the material to set . www.indiandentalacademy.com
  77. 77. Instruct the patient to open the mouth remove the tray by applying equal pressure bilaterally. Evaluate the impression. www.indiandentalacademy.com
  78. 78. Copper Band or Tube Method The copper band is used to salvage an impression of multiple preparation where there is only vague margins on one or two preparation that are not adequately replicated in the impression. Fitting of the copper band to preparation A copper band is selected and annealed by heating on a flame and quenching in alcohol. Mark the finish line with the explorer and round off the edges. evaluate the fit and cut orientation hole in top one fifth of the facial surface . www.indiandentalacademy.com
  79. 79. Copper band with orientation holes www.indiandentalacademy.com
  80. 80. Copper band contoured www.indiandentalacademy.com
  81. 81. Evaluating the fit of the copper band The circumference of the copper band must be such that it will fit over the preparation and still project into the gingival crevice. An oversize band should not be used since it will impinge on the gingival tissues. www.indiandentalacademy.com
  82. 82. Making the compound plug The red stick compound is heated over the Bunsen flame . Insert the warm compound mass to fill approximately the top third of the copper band. Seat and orient on to preparation and compress excess in to the band. The compound should just touch the occlusal surface . Remove and evaluate the impression, only the occlusal surface should be impressed. Remove 0.2mm of the compound to create space for the heavy body poly vinyl silicone. Drill a hole through the centre of the compound plug. www.indiandentalacademy.com
  83. 83. Making the impression. Make 4 to 5 holes evenly distributed above the bottom of the copper tube for the retention of the impression material. Coat the internal surface sparingly with adhesive . Clean and isolate the preparation. Mix heavy viscosity material and inject in to the band and position it on the tooth. Wait the material to set remove the band and inspect the impression www.indiandentalacademy.com
  84. 84. Copper band with the final impression www.indiandentalacademy.com
  85. 85. Reversible hydrocolloid technique This impression technique requires a special conditioning unit which consists of 3 thermostatically controlled water baths. 1. A liquefaction bath . 2.A storage bath . 3.A tempering bath. www.indiandentalacademy.com
  86. 86. Rimlock trays with stops www.indiandentalacademy.com
  87. 87. Procedure Select the correct size of water cooled impression trays. Place small modeling compound or prefabricated stops in the tray to prevent over seating . Fill the impression tray with heavy bodied material from the storage bath and place it in the tempering bath Load the syringe material in the syringe and replace it in the storage bath. Carefully remove the retraction cord and flood the tooth with water. www.indiandentalacademy.com
  88. 88. Inject the syringe material on the tooth cover the entire tooth. Remove the impression tray from the bath wipe with the gauze and place it in the mouth. After seating cold water is circulated through the tray until the impression material is set. Remove the impression with a rapid motion, wash with cold water ,evaluate for accuracy. www.indiandentalacademy.com
  89. 89. Removal of the retraction cord www.indiandentalacademy.com
  90. 90. Injecting hydrocolloide into the sulcus www.indiandentalacademy.com
  91. 91. Final impression in reversible hydrocolloid www.indiandentalacademy.com
  92. 92. The matrix impression system  The system uses a custom matrix to control the sulcular environment and to deliver the impression material to the subgingival to be immersed, it also incorporates the Attributes of traditional impression methods and overcomes in partial the deficiencies in registration of the subgingival Margins, gingival retraction and relapse, homeostasis and sulcular cleaning strengthening the sulcular flange of impression and simplification for making complex impressions. www.indiandentalacademy.com
  93. 93. The system uses three impression materials  A suitable elastomeric semi rigid material to form the matrix.  A high viscosity elastomeric impression material which will preferably bond to the matrix forming material, required to make an impression of the preparation of the matrix  A stock tray with medium viscosity elastomeric impression material to pick up the matrix impression and remaining arch not covered by the matrix.  Carrier for matrix forming material, it may be either custom made or stock available. www.indiandentalacademy.com
  94. 94. Matrix impression material :  This material is used to fill the matrix and generate the critical portion of the impression.  It would be a high viscosity material to facilitate the displacement of the gingival and to effectively flush the debris out of the sulcus.  High viscosity polyether is preferable for this procedure. www.indiandentalacademy.com
  95. 95. Tray impression material:  The impression material that is placed in the stock tray should be compatible with and bond to the matrix forming material and the impression material lining the matrix.  The viscosity of the tray material should be considerably less than that of the matrix material to facilitate impression removal because the matrix manages the critical portion of the impression removal because the matrix manages the critical portion of the impression; a stock tray is used to incorporate the matrix and the remaining teeth in the arch. www.indiandentalacademy.com
  96. 96. Matrix forming material :  On setting this impression material needs to provide a semi rigid matrix .  The matrix forming material should register details equal to the best impression materials  Matrix forming materials should be rapid setting and compatible with matrix impression and tray impression materials. www.indiandentalacademy.com
  97. 97.  Many paired material will bond at the time of contact when their unpolymerized material comes into contact with the polymerized component. Substantial forces are generated .  On removal delaminating may occur within the matrix. Polyether adhesive is most effective for non- bonding pair of materials. www.indiandentalacademy.com
  98. 98. Clinical procedures :  Immediately after tooth preparation and before any retraction procedures, select or create a carrier for the matrix forming material.  The carrier can be a manufactured product in various shapes and sizes in the office with vacuum forming equipment or may be made with wax directly in the mouth.  The carrier should provide 3-4 mm space between its wall and the prepared teeth and 2-3mm between its walls and adjacent unprepared teeth. It should extend to one tooth beyond the prepared tooth on both sides when the teeth are present. www.indiandentalacademy.com
  99. 99.  It should also extend 2-3mm on the ridge beyond the margin of the gingiva. All the soft tissue under the preplanned pontics and precision attachments should be included in the carrier.  Fill the carrier with Ramitec or PUS occlusal registration material and position it over the prepared teeth. The carrier should be held to create a 1-2mm thick occlusal wall over the unprepared teeth.  After the material polymerizes, remove the impression from the mouth and separate the matrix from the carrier. Trim it with a scalpel. www.indiandentalacademy.com
  100. 100.  Place the retraction cord around each prepared tooth leaving one end of the cord protruding 2-3mm for easy retrieval. A moist cord will prevent the chances of gingival bleeding, when it is removed. Any blood in the sulcus during retraction procedure should be cleaned. No dried blood should be left on the prepared teeth, since it cannot be removed from the tooth with the impression material.  Make high viscosity material and load in a conventional impression syringe. dispense the material to fill in the preparation depression of the matrix then apply the material generously on all the soft tissue side .this must be done in a manner as not to trap air in the occlusal recesses . Unlike other procedures, vent holes in the matrix should not be placed in an attempt to prevent air entrapment. www.indiandentalacademy.com
  101. 101.  Remove all retraction cords optionally; additional material from the syringe may be dispensed around the preparation .it is not essential to direct this material into the sulcus because this objective will be accomplished by the matrix. Additional material is pushed ahead to flush out debris from the sulcus . this step is considered to be more valuable when the prepared teeth are small in dimension and less material is available within the matrix  Seat the filled matrix on the prepared teeth (the adjacent teeth and structures help for orientation. excessive force should not be applied a vertically directed force should be applied with light pressure www.indiandentalacademy.com
  102. 102.  Immediately make a mix of medium viscosity impression material, load the stock tray seat the stock tray over the seated matrix impression.  After the impression materials are completely set, remove the impression and examine it for defects the matrix is often visible through the matrix impression material. This is acceptable.  When the impression is acceptable, form the master cast according to the desired procedure.  Keeping one half to two thirds of a tooth beyond the prepared tooth or teeth will help index the positioning of the matrix. www.indiandentalacademy.com
  103. 103.  Remove the excess material that extend to the facial and lingual portions The final matrix should delineate the occlusal surface on axial walls of the preparation and the crest of the gingival tissue because gingival retraction has not been implemented ,the crevice between the prepared tooth surfaces and gingival tissue should also be discernible.  When their crevice has not been recorded or if large voids have occurred in the matrix it should be remade. Unlike tube /coping techniques, it is not important to register the finish line at this stage .it is the crest of the gingival tissue that has to be recorded in the matrix.  If the impression of the preparation is made at a later visit, label the matrix and set it aside for trimming, when the impression is to be made during the preparation visit proceed with refining the matrix. www.indiandentalacademy.com
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  107. 107. Summary A good impression is an exact replica of each prepared tooth and should include adequate amount of the unprepared surfaces adjacent to the margin. Impression technique and material should be selected on the basis of biologic factor dictated by the anatomy and the physiology of the mouth dictated by the orofacial tissues. Even though there are innumerable techniques and procedure for impression making ,it is the responsibility of the dentist to select the best possible procedure based on sound knowledge , for achieving the best possible result for the patient. www.indiandentalacademy.com
  108. 108. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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