Impression Trays in Dentistry
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Questions and Answers

What is a common issue associated with the finger adaption method for resin impression trays?

  • Over-thinning of the impression tray material. (correct)
  • Under-thinning of the material due to insufficient pressure.
  • Inability to achieve a smooth texture during curing.
  • Improper cooling resulting in distorted shapes.

    • What is the correct stage of resin application during the finger adaptation process?

  • Dough stage. (correct)
  • Liquid stage.
  • Solid stage.
  • Gel stage.

    • Which of the following steps is included in the vacuum adapted method for creating impression trays?

  • Cooling the resin sheet before application.
  • Centering the cast on the vacuum adapter plate. (correct)
  • Trimming the cast before heating the resin.
  • Applying relief with melting materials.

    • What is the primary disadvantage of the shellac method for impression trays?

    <p>It is unstable and ineffective.</p> Signup and view all the answers

    What problem can arise from failing to roll the resin to a uniform thickness during the finger adapted method?

    <p>It can lead to thick trays that require more finishing time.</p> Signup and view all the answers

    What material is typically used for handles on vacuum adapted impression trays?

    <p>Auto polymerizing acrylic.</p> Signup and view all the answers

    What step follows after heating the resin sheet in the vacuum adaptation process?

    <p>Lowering the frame and resin sheet onto the cast.</p> Signup and view all the answers

    How should the impression tray be stored after it has been trimmed?

    <p>On the cast.</p> Signup and view all the answers

    What thickness should the handle of the impression tray be?

    <p>4mm</p> Signup and view all the answers

    What can be applied to assist in the bonding of the handle to the impression tray?

    <p>Liquid monomer</p> Signup and view all the answers

    Which method is identified as better for modified acrylic tray resins?

    <p>Finger adapted dough method</p> Signup and view all the answers

    What is a common problem when using the sprinkle-on method?

    <p>Difficulty controlling thickness</p> Signup and view all the answers

    What should be done to prevent the tray from breaking in areas with severe undercuts?

    <p>Tilt the cast during the process</p> Signup and view all the answers

    How thick should the resin layer be during the dough stage for an impression tray?

    <p>4mm</p> Signup and view all the answers

    What is the effect of applying too much finger pressure when adapting the material to the cast?

    <p>Over-thins the resin</p> Signup and view all the answers

    What should be applied to both the cast and relief wax before forming the impression tray?

    <p>Tinfoil substitute</p> Signup and view all the answers

    What is the primary purpose of taking an impression of the posterior region after removing posterior teeth?

    <p>To make a denture</p> Signup and view all the answers

    Which impression method involves using a one-piece full-arch impression tray?

    <p>Finger-adapted dough method</p> Signup and view all the answers

    What is the first step in the finger-adapted dough method for creating a full-arch impression tray?

    <p>Place the outline of the tray on the cast</p> Signup and view all the answers

    Which method is considered preferable for constructing full-arch trays due to its adaptation technique?

    <p>Finger-adapted dough method</p> Signup and view all the answers

    What is a key disadvantage of the vacuum-adapted method for constructing impression trays?

    <p>Need for specialized equipment</p> Signup and view all the answers

    In the finger-adapted dough method, what should be done immediately before reaching the dough stage?

    <p>Remove some material from the container</p> Signup and view all the answers

    What must be done to the tray before curing in the finger-adapted dough method?

    <p>Roll it into the desired thickness</p> Signup and view all the answers

    What is an identified problem in the finger-adapted dough method?

    <p>Difficulty maintaining tray thickness</p> Signup and view all the answers

    What is the primary function of an impression tray?

    <p>To carry and confine impression material in the mouth</p> Signup and view all the answers

    Which of the following is NOT a requirement for impression trays?

    <p>The tray must only be thick to withstand pressure</p> Signup and view all the answers

    What materials can be used to make impression trays?

    <p>Thermoplastic resin sheets</p> Signup and view all the answers

    Which method is commonly utilized for constructing resin impression trays?

    <p>The sprinkle-on method</p> Signup and view all the answers

    What is an important consideration when adapting layers of baseplate wax to a cast?

    <p>It must be 2mm shorter than the cast outline</p> Signup and view all the answers

    What role does tinfoil substitute play in the impression tray construction process?

    <p>To provide a barrier against the impression material</p> Signup and view all the answers

    How can an impression tray be modified after construction?

    <p>By grinding, trimming, or thinning</p> Signup and view all the answers

    Which statement about autopolymerizing resin impression trays is false?

    <p>They must be thick to maintain rigidity</p> Signup and view all the answers

    What is the purpose of allowing the tray to cool before trimming the borders?

    <p>To achieve a smoother finish on the tray</p> Signup and view all the answers

    Why is it important to block out spaces between teeth when making a tray?

    <p>To prevent resin from entering spaces between the teeth</p> Signup and view all the answers

    What is a likely consequence of using sheets that are too thin for the tray?

    <p>Flexible trays that may not hold shape</p> Signup and view all the answers

    What should be done before turning on the heater in the vacuum adapter?

    <p>Position a sheet of resin of proper thickness</p> Signup and view all the answers

    When is it specified to perforate the tray during the preparation process?

    <p>To enhance retention of the impression material</p> Signup and view all the answers

    What should be done to enhance the adaptation of wax to the cast?

    <p>Use a tinfoil substitute for relief</p> Signup and view all the answers

    What is the recommended action if sagging does not reach the recommended amount?

    <p>Adjust the heating time accordingly</p> Signup and view all the answers

    How should the tray be stored once completed?

    <p>On the cast itself</p> Signup and view all the answers

    Study Notes

    Impression Trays

    • Impression tray: A receptacle or device used to carry impression material to the mouth, confining the material to the surfaces to be recorded, and controlling the impression material while it sets, forming the impression.
    • Requirements for impression trays:
      • Rigid but not overly thick.
      • Retains its shape during construction and impression pouring.
      • Simple construction method for minimal time and cost.
      • Easily trimmed or thinned with burs, mounted stones, or scissors.
      • Smooth to prevent injury to oral tissues.
    • Impression tray materials:
      • Special autopolymerizing acrylic resin.
      • Conventional autopolymerizing acrylic resin.
      • Thermoplastic resin sheets.
      • Thermoplastic shellac baseplate materials.
      • Vacuum or pressure-adapting devices.
    • Autopolymerizing resin impression trays:
      • Easy to use and no special equipment required.
      • Can be thin but rigid.
      • Easily modified by grinding and smoothing to polish.
      • Two methods: sprinkle-on and finger-adapted dough.
    • The sprinkle-on method:
      • Commonly used for acrylic resin baseplates, also for resin impression trays.
      • Dentist specifies amount and placement of relief based on the impression material (e.g. sharp bones, hyperplastic tissues).
    • Procedure for creating an impression tray (using a cast):
      • Making an outline of the impression tray on the cast.
      • Blocking out severe undercuts.
      • Adapting a layer of baseplate wax to the cast for relief.
      • Placing tissue stops on the relief wax.
      • Painting a tinfoil substitute on the stone cast and the relief wax.
    • Procedure for maxillary cast:
      • Scribe red line at the depth of the vestibule.
      • Scribe blue line 2mm above the red line.
      • This determines tray extension.
      • Block out undercut areas like the frenum, buccal surfaces of tuberosity, rugae, and flabby alveolar ridges.
    • Mixing and curing the impression tray:
      • Sift powder polymer onto the cast and relief wax.
      • Saturate with liquid monomer until a 2mm thick uniform coating is created.
      • Cure under an inverted bowl or pressure pot.
    • Finishing and Handling:
      • Incorporating a handle (4mm thick and 8mm long) from mixed dough resin.
      • Wetting the resin attachment point with liquid monomer aids in bonding.
      • Removing tray from the cast after setting.
      • Trimming with a bur.
      • Finishing and polishing to eliminate discomfort for the patient.
      • Storing the finished tray on the cast.
    • Problem areas for the sprinkle-on method:
      • Difficulty controlling the thickness.
      • Tilting the cast during the process can compensate for the flow characteristics.
      • Severe undercuts pose breakage risk
      • Finger-adapted dough method is preferable for modified acrylic tray resins.
    • Finger-adapted dough method:
      • Extensive use in making resin trays.
      • The resin tray material is shaped to a dough to be thinned and adapted to the cast.
      • Procedure:
        • Place the tray outline on the cast.
        • Block out the teeth with base plate wax.
        • Adapt a layer of base plate wax over the cast then trim.
        • Paint tinfoil on the cast and the relief wax.
        • Proportion the auto-polymerizing resin and mix it.
        • Immediately before reaching the dough stage, remove a portion of the resin mix and place in border area of cast and roll the resin.
        • Hand-adapt the material carefully to avoid over-thinning.
        • Remove excess tray material from the cast borders.
        • Form the excess material into handles. Smooth area around the handle, use liquid monomer to improve bonding.
        • Make handles small for shorter finish time.
        • Continue adaptation to prevent rebound.
        • Cure the tray on a bench or in a bowl/pressure pot.
        • Remove, trim, smooth and finish borders.
        • Use teeth that project out from the cast as handles.
        • Remove any block out
        • If required, perforate the tray for elastic impression material
        • Store on the cast.
        • Problem areas include difficulty maintaining tray thickness, overall bulk.
    • Vacuum-adapted method:
      • Uses thermoplastic sheets.
      • Requires specialized equipment (vacuum or pressure machine) to adapt the sheet to the cast.
      • Different colors, thicknesses, and flexibility options available.
    • Shell-ac method:
      • Obsolete due to material instability.
    • Impression trays for immediate dentures:
      • Presence of teeth alters tray method (e.g. traditional vs. immediate)
      • Posterior teeth are sometimes removed to create a healing period to make an impression of the posterior region, making a denture, and then removing anterior teeth.
    • Full-arch impression trays:
      • Three methods used (finger-adapted dough, vacuum, sprinkle-on)
    • Custom posterior trays:
      • Another method to tray over posterior edentulous area of the case,
      • Another impression then is made over teh teeth and anterior vestibules with a stock tray
      • Can be made with finger-adapted dough, sprinkle-on, or vacuum-adapted methods
    • Two-piece trays:
      • Method using two impression trays.
      • One part first over posterior edentulous cast, then the second stage fits over the first.
    • Additional Procedures (general):
      • Placing outlines on casts
      • Beading outlines on casts with a sharp instrument for trimming,
      • Blocking wax where necessary for relief,
      • Utilizing tinfoil,
      • Mixing resin in a suitable container.
      • Adapting the material to the cast.

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    Chapter 3 Impression Trays PDF

    Description

    This quiz covers the essential aspects of impression trays in dentistry, detailing their requirements, materials, and construction methods. Test your knowledge on the properties and uses of various impression tray materials, including autopolymerizing resins and thermoplastic options.

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