5. Impressions Flashcards
What is the ideal thickness of alginate in a tray
5mm
What is the ideal thickness of elastomeric impression material in a tray
3mm
Compare the goals of obtaining an impression of a dentate arch compared to a partially edentulous arch
Dentate
- Capture teeth
- More tolerant to impression errors
Partially edentulous
- Capture all teeth (esp abutments)
- Surrounding tissue
- Edentulous areas
- Less error tolerant
Poor fit for stock trays is typically expected where
edentulous areas
regions where the stock tray is often under-extended is where
- Hard palate height
- Post dam distal edge of maxilla (hamular notch)
- Lingual extent of mandibular tray (FOM)
Where should you use your finger to wipe alginate
- Occlusal surfaces of teeth
- Proximal surfaces of teeth adjacent to edentulous areas
- Retromylohyoid fossa (syringe)
Correct W:P ratio for alginate is
dimensional accuracy
Dx casts are used to
- Evaluate occlusion and available space
- RPD survey and framework design
- Dx wax up if needed
- Construction of custom tray for secondary impression
What direction should the cast be moved on a survey table to alter the angulation of the guide planes
-anteroposteriorly
What direction should the cast be moved on a survey table to alter the angulation of the retentive areas
laterally
Latticework should extend how far buccally
1-2 mm beyond the crest of the ridge
Finish lines extend onto
proximal plates
Lateicwork joins the lingual bar where
at the midpoint
Minor connectors are _ to the major connector
pependicular (90 degrees)
The distance between the approach arm for an infrabuldge clasp and the gingival margin is
4mm
Retentive clasps are how wide… reciprocal
-1.5mm taper to 1mm when engaging the undercut …1.5 mm
Sequence for tooth mods
- guide planes
- HOC (acial surfaces aka B and L)
- Rest preps
How is a custom tray made for a partial denture
- 1 layer of wax over the edentulous regions and 2 over the teeth
- 1 layer over hypermobile tissue, thin and narrow crest of alveolar ridge (alternative is just 1 layer of wax over entire edentulous area)
Overall thickness of the custom tray should be
2-3 mm
Why should you vent the tray and where should you do it
- Why= relief area
- Primary v.s secondary support area (do in regions of tissue compressibility, sensitivity and resistance to resorption)
Hard prominent areas to relief on the maxilla
- median palatine raphe
- torus palatinus
Hard prominent areas to relieve on the mandible
- Torus mandibularis
- Genial tubercles (if prominent)
- Prominent mylohyoid ridge
Sensitive areas on the maxilla that require relieving
- Incisive papilla
- Rugae
- Flabby ridge
- Sharp bony spicules
Sensitive areas on the mandible to relieve
- Mental forame in resorbed ridges
- Flabby tissue
- Sharp bony spicule
