Impressions for fpd / implant dentistry course


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  • To obtain an impression is the first step in indirect fabrication of a prosthesis.. And fixed prosthodontics is practised as indirect restorations
  • Plasticity-ability to be shaped
  • Agar-organic hydrophilic colloid(polysaccharide) extracted from certain sea weeds.
  • Potassium titanium fluoride –accelerator for setting of gypsum
  • W/P ratio is specified by the manufacturer. Mixing is done in a clean bolw with a wide bladed spatula.. The mixing is started in circular to wet the powder with water and later spatulation is done by swiping it against the side of the bowl. A figure of 8 motion can be used.
  • They were introduced in 1950 s . They were acceptable due to dimensional stability and tear resistance when compared to hydrocolloid impression mateials.
  • There is a slight contraction in these materials during polymerisation but this can be compensated by custom trays since bulk is reduced
    The main component is multifunctional mecaptan or polysulfide polymer. Plasticizer to get appropriate viscosity of paste.sulphur to accelerate the reaction
  • Why catalyst is mixed over the base.
  • Polydimethy siloxane reacts with tetraethyl orthosilicate in presence of stannous octoate to give ethyl alcohol
  • Base paste contains amine terminated polyether polymer with is cross linked with aromatic sulfonate ester
  • Autoplymerised,thermoplastic and photopolymerised resin
  • Black lines indicate sulcular extension and proximal contacts .
  • Nachum etal did a study to evaluate the fpd impressions
  • Hung etal did a study to evaluate the accuracy of one step vs two step putty wash impression techniques
  • Impressions for fpd / implant dentistry course

    1. 1. IMPRESSIONS IN FIXED PARTIAL DENTURESINDIAN DENTAL ACADEMY Leader in continuing dental education
    3. 3.  .
    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.
    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
    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
    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
    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.
    10. 10.  Condensation Silicone- Early 1960’s  Addition Silicone-1970’s  Polyether- Late 1970’s  Polyether Urethane Dimethacrylate - Late 1980’s
    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.
    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
    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 called as Negacol  Later Poller's 'Negacoll’ was modified and introduced to the dental profession as 'Dentacol’ in 1928.
    14. 14. Example  Slate Hydrocolloid (Van R)  Cohere  Superbody  Super syringe
    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
    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
    17. 17. Advantages  Accurate reproduction of surface detail  Hydrophilic  displace moisture, blood, fluids  Inexpensive  No custom tray or adhesives  No mixing required
    18. 18. Disadvantages  Initial expense  special equipment  Material should be prepared in advance  Tears easily  Dimensionally unstable  Pour immediately  Single cast  Difficult to disinfect
    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  Zelgan, jeltrate (Dentsply)  Coe Alginate (GC America)  Integra(kerr)
    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
    21. 21. Setting reaction: (gelation process) 2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4 Na alginate + CaSO4 Ca alginate + Na2SO4 (powder) (gel) H2O
    22. 22. Modified alginates  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.
    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
    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.
    25. 25. Manipulation
    26. 26. Mechanical mixing devices
    27. 27. Advantages:  Inexpensive  Easy to use  Hydrophilic  displace moisture, blood, fluids  Stock trays
    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
    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.
    30. 30.
    31. 31. Polysulfide  The first elastomer used for dental impressions Examples  Permlastic (Kerr)  Omni-Flex (GC America) – copper hydroxide system  Coe-flex( GC America)
    32. 32.  Available in 3 viscosities,  light body and medium body ,heavy body.
    33. 33. 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.
    34. 34.  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.
    35. 35. Advantages Disadvantages  Long working time  High tear resistant  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
    36. 36. SILICONES
    37. 37. CONDENSATION SILICONE  Condensation reaction – a polymerization reaction in which the polymer chains grow simultaneously and a reaction byproduct is ethanol Available In Three Viscosities:  Light body  Medium body  Putty body Supplied as:  Paste – two pastes in collapsible tubes  Putty – jars
    38. 38. Examples:  Speedex (Coltene/Whaledent)  Primasil (TISS Dental)  Accoe (GC-Amer)  Xantopren (Unitek)  Elasticon (Kerr)
    39. 39. 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
    40. 40. Advantages:  Better elastic properties  Clean, pleasant  Stock tray  Good working and setting time Disadvantages: Permanent deformation – high – 1-3% Poor dimensional stability high shrinkage  Hydrophobic
    41. 41. ADDITION SILICONES  Frequently called polyvinylsiloxane or vinyl polysiloxane impression materials. Supplied in 4 viscosities  Light body  Medium body  Heavy body  Putty
    42. 42. Examples:  Extrude (Kerr)  Express (3M/ESPE)  Aquasil (Dentsply )  Virtual (Ivoclar Vivadent)
    43. 43. 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
    44. 44. 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
    45. 45. POLYETHER  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
    46. 46. Examples  Impregum F (3M/ESPE)  Permadyne (3M/ESPE)  Pentamix (3M/ESPE)  P2 (Heraeus Kulzer)  Polygel (Dentsply )
    47. 47.
    48. 48. Advantages  Highly accurate  Good dimensional stability  hydrophilic  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
    49. 49. Impression Techniques  1. Stock tray technique/putty wash technique - Double mix - Single mix  2. Custom tray technique - Single mix - Double mix  3. Closed bite double arch technique  4. Copper band technique  5. Reversible hydrocolloid technique
    50. 50. STOCK TRAY IMPRESSION TECHNIQUE (Putty wash technique): Mixing method: Double mix and single mix Procedure :  Place patient in supine 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.
    51. 51.  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.
    52. 52.  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.
    53. 53. 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.
    54. 54.  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.
    55. 55.  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.
    56. 56. SINGLE MIX TECHNIQUE:  For the stock tray Single mix insert the low viscosity impression material into the prepared area  Putty material is loaded into the stock tray  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.
    57. 57. 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.
    58. 58.  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.
    59. 59. 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.
    60. 60. 2)Adapt a wax spacer to the diagnostic cast two layers for 2.5mm thickness approximately.
    61. 61. Tray Stops
    62. 62. 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.
    63. 63. Tray handle is made Borders are trimmed and the tray is polished
    64. 64. Lateral wings can be made which will help in easy removal of the tray
    65. 65. Prepare syringe:  Lubricate the syringe lightly.  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).
    66. 66. Making the final impression. Medium or high viscosity is used in the tray and low viscosity in the syringe. The low viscosity material syringed in the prepared site. The high viscosity material is placed in the custom tray and seated in the mouth.
    67. 67. The impression is removed and evaluated.
    68. 68. 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.
    69. 69. Advantages maximum intercuspation position 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
    70. 70. 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.
    71. 71. 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 .
    72. 72. Instruct the patient to open the mouth remove the tray by applying equal pressure bilaterally. Evaluate the impression.
    73. 73. 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 on facial surface .
    74. 74. Copper band with orientation holes
    75. 75. Copper band contoured
    76. 76. 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.
    77. 77. Making the compound plug The green 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.
    78. 78. Making the impression. 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 for the material to set remove the band and inspect the impression
    79. 79. Copper band with the final impression
    80. 80. 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.
    81. 81. Rimlock trays with stops
    82. 82. 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.
    83. 83. 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.
    84. 84. Final impression in reversible hydrocolloid
    85. 85. Laminate Technique (or) Agar Alginate Combination Technique  After injecting the syringe agar on to the area to be recorded, an impression tray containing a mix of chilled alginate that will bond with the syringe agar is positioned on it.  The alginate gels by a chemical reaction, whereas the agar gels by means of contact with the cool alginate rather than the water circulating through the tray.
    86. 86. Advantages 1. Less air bubbles 2. Water cooled trays are not required 3. It sets faster than the regular agar technique.
    87. 87. Wet Field Technique  This is relatively new technique which has become popular.the areas to be recorded are actually flooded with warm water.  Then the syringe material is introduced quickly, liberally and in bulk to cover the occlusal and/or incisal areas only.  while the syringe material is still liquid, the tray material is seated.
    88. 88.  The hydraulic pressure of the viscous tray materials forces the fluid syringe hydrocolloid down into the areas to be recorded.  This motion displaces the syringe materials as well as blood and debris throughout the sulcus
    89. 89. The matrix impression system Gus J. Livaditis jpd 1998, vol 79,issue 2  The system uses a custom matrix to control the sulcular environment and to deliver the impression material subgingivally . It also incorporates the attributes of traditional impression methods and overcomes partial the deficiencies of impression making such as registration of the subgingival Margins, gingival retraction and relapse, hemostasis and sulcular cleaning, strengthening the sulcular flange of impression and simplification for making complex impressions.
    90. 90. The system uses three impression materials  1.A suitable elastomeric semi rigid material to form the matrix.  2. 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  3. 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.
    91. 91. Clear plastic carrier selected from assortment of premade forms. Matrix is made in carrier with polyvinyl siloxane material before soft tissue is retracted. Immediately after tooth preparation and before any retraction procedures
    92. 92.  Black Lines Indicate Sulcular extension. Thick red line indicates crest of gingiva. Two black marks point out proximal contacts that must be relieved. Slender bur or knife edged rubber wheel used to enlarge interproximal embrasures. Matrix should extend one half to two thirds of tooth beyond prepared teeth and close to gingival crest.
    93. 93. syringe is used to fill matrix with high viscosity impression material. Matrix impression is seated with light pressure. Stock tray filled with medium viscosity impression material is seated over matrix impression before matrix material polymerizes.
    94. 94. REVIEW OF LITERATURE  Nachum Samet DMD, Michael Shohat DMD, Alon Livny DMD and Ervin I. Weiss DMD: A clinical evaluation of fixed partial denture impressions; J Prosthet Dent, volume 94, issue 2, August 2005, pages 112 – 117: This study evaluated the quality of impressions sent to commercial laboratories for the fabrication of fixed partial dentures (FPD) by describing the frequency of clinically detectable errors and by analyzing correlations between the various factors involved. Within the limitations of this study, impressions made with polyethers had the most detectable errors, followed by condensation-type silicones. The high frequency of detectable errors found in impressions sent for FPD fabrication is of concern.
    95. 95.  Hung SH, Purk JH, Tira DE, Eick JD : Accuracy of one-step versus two-step putty wash addition silicone impression technique; J Prosthet Dent 1992 May; 67(5):583-9: This study compared the accuracy of one-step putty wash with two-step putty wash impression techniques. Five addition silicone impression materials-Mirror 3 (MR), Mirror 3 Extrude (ME), Express (E), Permagum (P), and Absolute (A)-- were tested. A stainless steel model containing two full-crown abutment preparations was used as the positive control. Five replications for one-step and two-step putty wash impressions of the master model were made for each test material. Accuracy of the materials was assessed by measuring six dimensions on stone dies poured from impressions of the master model. Accuracy of addition silicone impression material is affected more by material than technique. Accuracy of the putty wash one-step impression technique was not different from the putty wash two-step impression technique except at one of the six dimensions where one-step was more accurate than two-step. Mirror 3 putty wash two-step impression presented less distortion than Mirror 3 Extrude putty wash one-step or two-step impression.
    96. 96.  Nissan J, Laufer BZ, Brosh T, Assif D : Accuracy of three polyvinyl siloxane putty-wash impression techniques; J Prosthet Dent. 2000 Feb; 83(2):161-5; This study assessed the accuracy of 3 putty-wash impression techniques (1) 1-step (putty and wash impression materials used simultaneously); (2) 2-step with 2-mm relief (putty first as a preliminary impression to create 2-mm wash space with prefabricated copings. In the second step, the wash stage was carried out); and (3) 2-step technique with a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). using the same impression material (polyvinyl siloxane) in a laboratory model. For each technique, 15 impressions were made of a stainless steel master model that contained 3 complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring 6 dimensions on stone dies poured from impressions of the master model. CONCLUSION: The polyvinyl siloxane 2-step, 2-mm, relief putty-wash impression technique was the most accurate for fabricating stone dies.
    97. 97. 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.
    98. 98. REFERENCES  1.Phillips science of dental materials – 11th edition – Anusavice  2.fundamentals of fixed prosthdontics- 3rd edition Herbert T.Shillingburg  3.Dental Materials – E. C. Coombe  4.Applied Dental Materials – 8th Edition – McCabe  5.Contemporary Fixed Prosthodontics – 3rd edition Stephen F.Rosenstiel
    99. 99. 1.Nachum Samet DMD, Michal Shohat DMD, Alon Livny DMD and Ervin I. Weiss DMD: A clinical evaluation of fixed partial denture impressions; J Prosthet Dent, volume 94, issue 2, August 2005, pages 112 – 117. 2.Hung SH, Purk JH, Tira DE, Eick JD : Accuracy of one-step versus two-step putty wash addition silicone impression technique; J Prosthet Dent. 1992 May; 67(5):583-9. 3. Laufer BZ, Brosh T, Assif D : Accuracy of three polyvinyl siloxane putty-wash impression techniques; J Prosthet Dent. 2000 Feb; 83(2):161
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