Impression techniques and materials partial dentures yr 3

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Text of Impression techniques and materials partial dentures yr 3

  • IMPRESSION TECHNIQUE IMPRESSION TECHNIQUE AND MATERIALSAND MATERIALS

    DR ZURYATI AB GHANIDR ZURYATI AB GHANI

    BDS (WALES), Grad Dip BDS (WALES), Grad Dip ClinClin Dent (Adelaide), Dent (Adelaide), Doctor in Clinical Dentistry (Doctor in Clinical Dentistry (prosthodonticsprosthodontics), ),

    Adelaide, FRACDS (Australia).Adelaide, FRACDS (Australia).

    24.06.0724.06.07

  • Impressions Impressions

    An impression An impression an imprint produced an imprint produced by by the pressure of one thing upon or the pressure of one thing upon or into the surface of anotherinto the surface of another

    Active rather than passive roleActive rather than passive role Making rather than taking Making rather than taking Flawed impressions account for the Flawed impressions account for the

    majority of denture problemsmajority of denture problems

  • PRIMARY IMPRESSIONPRIMARY IMPRESSION

    DefinitionDefinition--an impression made for the an impression made for the purpose of diagnosis or for the construction purpose of diagnosis or for the construction of a trayof a tray

  • Tray selectionTray selection

    stock trays: dentatestock trays: dentate metal or plasticmetal or plastic 22--3 mm clearance between stock 3 mm clearance between stock

    tray and ridgetray and ridge

  • Stock trayStock tray

  • Materials for primary Materials for primary impressionimpression AlginateAlginate

  • Secondary or definitive Secondary or definitive impressionimpression

    DefinitionDefinition An imprint that record the entire functional An imprint that record the entire functional

    denturedenture--bearing area to ensure maximum bearing area to ensure maximum support, retention and stability for the denture support, retention and stability for the denture during useduring use

    Primary purposePrimary purpose To record accurately the tissues of the denture To record accurately the tissues of the denture

    bearing areas, in addition to recording the bearing areas, in addition to recording the functional width and depth of the sulci functional width and depth of the sulci

  • Secondary impressionSecondary impression

    Conventional techniques Conventional techniques Selective pressure techniquesSelective pressure techniques Functional techniquesFunctional techniques Reline and rebases techniquesReline and rebases techniques

  • Conventional techniqueConventional technique

    Also known as Also known as Anatomical orAnatomical or MucostaticMucostaticThe surface contour of the ridge is The surface contour of the ridge is

    recorded at its resting form (no recorded at its resting form (no occlusalocclusal load)load)

  • Special traysSpecial trays

  • Conventional techniqueConventional technique

    Material of choice (soft or less viscous Material of choice (soft or less viscous impression material)impression material)alginate, alginate,

    Disadvantages: In freeDisadvantages: In free--end saddle end saddle dentures, distal end will show dentures, distal end will show tissuewardtissueward movement under movement under occlusalocclusalloadloadridgeridge resorptionresorption

  • Conventional techniqueConventional technique

    recommended for tooth supported recommended for tooth supported partial denturespartial dentures--KennedyKennedys class III and IVs class III and IV--These are bounded saddlesThese are bounded saddles

  • Functional impression Functional impression techniquetechnique

    Impressions are recorded under Impressions are recorded under functional load (pressure) i.e. Record functional load (pressure) i.e. Record tissue in a compressed formtissue in a compressed form

    Also known as: Also known as: MucocompressiveMucocompressiveimpressionimpression

  • Selective pressure Selective pressure techniquetechnique

    MucostatiocMucostatioc impressionimpressionANDAND

    MucocompressiveMucocompressive impressionimpression

  • Support in free end Support in free end saddlesaddle Support from tooth (rest seat) and soft tissue Support from tooth (rest seat) and soft tissue

    (mucosa)(mucosa) Tooth is rigid, mucosa is soft and displaceableTooth is rigid, mucosa is soft and displaceable During function, the free end saddle will be pushed During function, the free end saddle will be pushed

    towards the tissue and then bounces back. This towards the tissue and then bounces back. This movement may cause loosening of abutment tooth movement may cause loosening of abutment tooth and and resorptionresorption of alveolar bone.of alveolar bone.

    The aim is to create minimum movement of the The aim is to create minimum movement of the denture base during functiondenture base during function

    Therefore, selective pressure technique may be Therefore, selective pressure technique may be used to achieve this.used to achieve this.

  • Selective pressure Selective pressure techniquetechnique

    Kennedy Class I

  • 2 Techniques to achieve 2 Techniques to achieve selective pressure selective pressure impressionimpression Functional dual impression techniqueFunctional dual impression technique Altered cast technique or Applegate Altered cast technique or Applegate

    techniquetechnique

  • Functional dual Functional dual impressionimpression

    A functional A functional impression of the impression of the edentuluosedentuluos ridge is ridge is made.made.

    The 2The 2ndnd impression impression made over made over functional functional impression and impression and record structures in record structures in their anatomic formtheir anatomic form

  • Altered cast techniqueAltered cast technique

    Anatomical master impression of oral Anatomical master impression of oral structure is madestructure is made

    Construct master cast and refractory Construct master cast and refractory castcast

    Construct metal framework with Construct metal framework with temporary selftemporary self--cured acrylic resin cured acrylic resin saddlessaddles

  • Special tray construction for Special tray construction for selective pressure techniqueselective pressure technique

  • A viscous impression A viscous impression egeg impression impression wax heated to 65wax heated to 65C and painted onto C and painted onto surface of saddles, then placed inside surface of saddles, then placed inside mouth, to get satin finish impression mouth, to get satin finish impression of the ridgeof the ridge

    Other viscous impression material is Other viscous impression material is compoundcompound

  • Altered cast techniqueAltered cast technique

    In the lab, the saddle area is cut away from stone cast

  • The metal frame is The metal frame is located onto the located onto the abutment teethabutment teeth

    The saddle area is The saddle area is beaded and boxedbeaded and boxed

    The saddle area is The saddle area is cast (2cast (2--part stone part stone cast)cast)

  • Disadvantages of selective Disadvantages of selective pressure techniquespressure techniques Tissues are constantly compressed, and Tissues are constantly compressed, and

    can cause bone can cause bone resorptionresorption due to 2 due to 2 reasons:reasons:

    i)i) Constant pressure stimulate formation of Constant pressure stimulate formation of osteoclastsosteoclasts

    ii)ii) Constant pressure reduces blood supply, Constant pressure reduces blood supply, which simulates formation of which simulates formation of osteoclastsosteoclasts..

    If retentive clasps do not hold denture in If retentive clasps do not hold denture in place, the denture will be slightly place, the denture will be slightly occlusalocclusalto normal to normal positionpositionprematurepremature contact.contact.

  • Technique to be practiced in PPSG Technique to be practiced in PPSG Dental Clinic for free end saddleDental Clinic for free end saddle

    Single traySingle tray--spaced in dentate area and closed spaced in dentate area and closed fitting in free end saddle area.fitting in free end saddle area.

    Dual impression materialsDual impression materials-- alginate in dentate alginate in dentate area and area and ZnOEZnOE in saddle area.in saddle area.

    To ensure ideal adaptation in free end saddle.To ensure ideal adaptation in free end saddle. Conventional technique rather than selective Conventional technique rather than selective

    pressurepressure

  • Courtesy of Sofia

  • Courtesy of Sofia

  • ReferencesReferences

    Textbook of Textbook of ProsthodonticsProsthodontics. Deepak . Deepak NallaswamyNallaswamy. . JaypeeJaypee brothers medical brothers medical publishers (p) LTD. 2003publishers (p) LTD. 2003

    Notes on Notes on ProsthethicProsthethic dentistry.dentistry.MRY Dyer, BJ Roberts. Butterworth & Co MRY Dyer, BJ Roberts. Butterworth & Co 1989.1989.

    McCrackenMcCrackens Removable partial s Removable partial prosthodonticsprosthodontics. 11. 11thth edition. Elsevier, edition. Elsevier, MosbyMosby

    IMPRESSION TECHNIQUE AND MATERIALSImpressionsPRIMARY IMPRESSIONTray selectionStock trayMaterials for primary impressionSecondary or definitive impressionSecondary impressionConventional techniqueSpecial traysConventional techniqueConventional techniqueFunctional impression techniqueSelective pressure techniqueSupport in free end saddleSelective pressure technique2 Techniques to achieve selective pressure impressionFunctional dual impressionAltered cast techniqueSpecial tray construction for selective pressure techniqueAltered cast techniqueDisadvantages of selective pressure techniquesTechnique to be practiced in PPS