Impression Materials 1

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    IMPRESSION MATERIALS AND

    ITS MANIPULATIONAswathy.Brahmanandan

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    OUTLINE

    Reversible hydrocolloid (Agar)

    Non-aqueous Elastomers

    Impression trays custom tray fabrication

    Making an impression Preparing a tray Preparing the patient Preparing the material Impression technique

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    Impression Trays

    Impression trays can be:

    1. Stock trays.

    2. Custom trays.

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    Stock Trays

    Metal trays.Plastic trays.

    Perforated trays.

    Non perforated trays.

    Quadrant trays.

    Section trays.Full arch trays.

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    Custom Trays

    Custom trays improve the accuracy of elastomeric impressions.

    Elastomeric impression materials are moreaccurate in uniform, thin layers of 2-3 mm.

    The custom tray must be rigid and shouldhave stops on the occlusal surface.

    Clearance between the tray and the teethshould be 2-3 mm.

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    Custom Trays

    Custom trays can be made up of:

    1. Auto polymerized acrylic resin.

    2. Thermoplastic resin.

    3. Light polymerized resin.

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    Custom Trays Fabrication

    Armamentarium:Diagnostic cast.Base plate wax.Aluminium or tin foil.

    Spatula.Scalpel.Scissors.

    Auto polymerized acrylicresin.

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    Custom Trays Fabrication

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    Custom Trays Fabrication

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    Making an Impression

    Making impression with elastomericimpression material involves:

    Preparing a tray.

    Preparing the patient.

    Preparing the material.

    Impression technique.

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    Preparing the Patient

    Impression making requires recording the exactdimensions of the preparation, the position of thesoft tissue, the architecture of the margins of the

    preparation, and the relationship of the prepared

    teeth to the surrounding dentition.Isolate the prepared teeth with cotton rolls, placesaliva ejector and dry the field with air.

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    Preparing the Patient

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    Gums are retracted away from the tooth using a medicatedgingival retraction cord .

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    Preparing the Material

    Elastomeric impression materials can be:

    Light body Also referred to as syringetype, or wash type . This material is usedwith a syringe and placed directly on hard

    and soft tissuesPutty.

    Heavy body - referred to as tray type

    materials, which support the light-bodymaterial.

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    Preparing the Material

    Elastomeric impression materials can be provided as:

    Two paste system.

    Two putty system.Automixer and dispenser.

    Machine Mixing System.

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    Two Paste System

    Dispense the same length of material onto amixing pad or glass slab.Catalyst paste is collected on a spatula and

    distributed over the base .

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    Two Paste System

    The mixture is thoroughly spatulated until themixed paste is uniform in color with no streaks of

    base or catalyst appearing in the mixture.If one component is in liquid form, a length of the base paste is dispensed on a graduated mixing padand one drop of the liquid catalyst is added for

    each unit length of base.

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    Two Putty Systems

    Putty impression materials are dispensed byvolume using equal number of scoops of each

    putty.

    Kneed the material with your fingers until auniform color is obtained.

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    Automixer and Dispenser

    When the trigger is pulled, the plunger is driven forward, so that the base andcatalyst paste are forced from thecartridge into the mixing tip.The pastes pass through the bore andexit the nozzle as a uniform mixed

    paste.

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    Automixer and Dispenser

    The mixing tips vary in diameter, lengthand size of the tip opening for specificconsistency.

    The mixed impression material is injecteddirectly into the adhesive-coated tray or on to the prepared teeth.

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    Machine Mixing System

    Pentamix machine:Used for polyether impression material.Convenient and produce void-free impressions.

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