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Impression techniques and materials partial dentures yr 3

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Impression techniques and materials partial dentures yr 3

  1. 1. IMPRESSION TECHNIQUEIMPRESSION TECHNIQUE AND MATERIALSAND MATERIALS DR ZURYATI AB GHANIDR ZURYATI AB GHANI BDS (WALES), Grad DipBDS (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
  2. 2. ImpressionsImpressions An impressionAn impression –– an imprint producedan imprint produced byby ‘‘the pressure of one thing upon orthe 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 takingMaking rather than taking Flawed impressions account for theFlawed impressions account for the majority of denture problemsmajority of denture problems
  3. 3. PRIMARY IMPRESSIONPRIMARY IMPRESSION DefinitionDefinition--an impression made for thean impression made for the purpose of diagnosis or for the constructionpurpose of diagnosis or for the construction of a trayof a tray
  4. 4. Tray selectionTray selection stock trays: dentatestock trays: dentate metal or plasticmetal or plastic 22--3 mm clearance between stock3 mm clearance between stock tray and ridgetray and ridge
  5. 5. Stock trayStock tray
  6. 6. Materials for primaryMaterials for primary impressionimpression AlginateAlginate
  7. 7. Secondary or definitiveSecondary or definitive impressionimpression DefinitionDefinition An imprint that record the entire functionalAn imprint that record the entire functional denturedenture--bearing area to ensure maximumbearing area to ensure maximum support, retention and stability for the denturesupport, retention and stability for the denture during useduring use Primary purposePrimary purpose To record accurately the tissues of the dentureTo record accurately the tissues of the denture bearing areas, in addition to recording thebearing areas, in addition to recording the functional width and depth of the sulcifunctional width and depth of the sulci
  8. 8. Secondary impressionSecondary impression Conventional techniquesConventional techniques Selective pressure techniquesSelective pressure techniques Functional techniquesFunctional techniques Reline and rebases techniquesReline and rebases techniques
  9. 9. Conventional techniqueConventional technique Also known asAlso known as Anatomical orAnatomical or MucostaticMucostatic The surface contour of the ridge isThe surface contour of the ridge is recorded at its resting form (norecorded at its resting form (no occlusalocclusal load)load)
  10. 10. Special traysSpecial trays
  11. 11. Conventional techniqueConventional technique Material of choice (soft or less viscousMaterial of choice (soft or less viscous impression material)impression material) alginate,alginate, Disadvantages: In freeDisadvantages: In free--end saddleend saddle dentures, distal end will showdentures, distal end will show tissuewardtissueward movement undermovement under occlusalocclusal loadload→→ridgeridge resorptionresorption
  12. 12. Conventional techniqueConventional technique recommended for tooth supportedrecommended for tooth supported partial denturespartial dentures --KennedyKennedy’’s class III and IVs class III and IV --These are bounded saddlesThese are bounded saddles
  13. 13. Functional impressionFunctional impression techniquetechnique Impressions are recorded underImpressions are recorded under functional load (pressure) i.e. Recordfunctional load (pressure) i.e. Record tissue in a compressed formtissue in a compressed form Also known as:Also known as: MucocompressiveMucocompressive impressionimpression
  14. 14. Selective pressureSelective pressure techniquetechnique MucostatiocMucostatioc impressionimpression ANDAND MucocompressiveMucocompressive impressionimpression
  15. 15. Support in free endSupport in free end saddlesaddle Support from tooth (rest seat) and soft tissueSupport 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 pushedDuring function, the free end saddle will be pushed towards the tissue and then bounces back. Thistowards the tissue and then bounces back. This movement may cause loosening of abutment toothmovement may cause loosening of abutment tooth andand resorptionresorption of alveolar bone.of alveolar bone. The aim is to create minimum movement of theThe aim is to create minimum movement of the denture base during functiondenture base during function Therefore, selective pressure technique may beTherefore, selective pressure technique may be used to achieve this.used to achieve this.
  16. 16. Selective pressureSelective pressure techniquetechnique Kennedy Class I
  17. 17. 2 Techniques to achieve2 Techniques to achieve selective pressureselective pressure impressionimpression Functional dual impression techniqueFunctional dual impression technique Altered cast technique or ApplegateAltered cast technique or Applegate techniquetechnique
  18. 18. Functional dualFunctional dual impressionimpression A functionalA functional impression of theimpression of the edentuluosedentuluos ridge isridge is made.made. The 2The 2ndnd impressionimpression made overmade over functionalfunctional impression andimpression and record structures inrecord structures in their anatomic formtheir anatomic form
  19. 19. Altered cast techniqueAltered cast technique Anatomical master impression of oralAnatomical master impression of oral structure is madestructure is made Construct master cast and refractoryConstruct master cast and refractory castcast Construct metal framework withConstruct metal framework with temporary selftemporary self--cured acrylic resincured acrylic resin saddlessaddles
  20. 20. Special tray construction forSpecial tray construction for selective pressure techniqueselective pressure technique
  21. 21. A viscous impressionA viscous impression egeg impressionimpression wax heated to 65wax heated to 65°°C and painted ontoC and painted onto surface of saddles, then placed insidesurface of saddles, then placed inside mouth, to get satin finish impressionmouth, to get satin finish impression of the ridgeof the ridge Other viscous impression material isOther viscous impression material is compoundcompound
  22. 22. Altered cast techniqueAltered cast technique In the lab, the saddle area is cut away from stone cast
  23. 23. The metal frame isThe metal frame is located onto thelocated onto the abutment teethabutment teeth The saddle area isThe saddle area is beaded and boxedbeaded and boxed The saddle area isThe saddle area is cast (2cast (2--part stonepart stone cast)cast)
  24. 24. Disadvantages of selectiveDisadvantages of selective pressure techniquespressure techniques Tissues are constantly compressed, andTissues are constantly compressed, and can cause bonecan cause bone resorptionresorption due to 2due to 2 reasons:reasons: i)i) Constant pressure stimulate formation ofConstant pressure stimulate formation of osteoclastsosteoclasts ii)ii) Constant pressure reduces blood supply,Constant pressure reduces blood supply, which simulates formation ofwhich simulates formation of osteoclastsosteoclasts.. If retentive clasps do not hold denture inIf retentive clasps do not hold denture in place, the denture will be slightlyplace, the denture will be slightly occlusalocclusal to normalto normal positionposition→→prematurepremature contact.contact.
  25. 25. Technique to be practiced in PPSGTechnique to be practiced in PPSG Dental Clinic for free end saddleDental Clinic for free end saddle Single traySingle tray--spaced in dentate area and closedspaced in dentate area and closed fitting in free end saddle area.fitting in free end saddle area. Dual impression materialsDual impression materials-- alginate in dentatealginate in dentate area andarea 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 selectiveConventional technique rather than selective pressurepressure
  26. 26. Courtesy of Sofia
  27. 27. Courtesy of Sofia
  28. 28. ReferencesReferences Textbook ofTextbook of ProsthodonticsProsthodontics. Deepak. Deepak NallaswamyNallaswamy.. JaypeeJaypee brothers medicalbrothers medical publishers (p) LTD. 2003publishers (p) LTD. 2003 Notes onNotes on ProsthethicProsthethic dentistry.dentistry. MRY Dyer, BJ Roberts. Butterworth & CoMRY Dyer, BJ Roberts. Butterworth & Co 1989.1989. McCrackenMcCracken’’s Removable partials Removable partial prosthodonticsprosthodontics. 11. 11thth edition. Elsevier,edition. Elsevier, MosbyMosby

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