Impressions for dentures Flashcards
What is the ideal distance between the flange of the stock tray and the teeth?
4mm.
- If not 4mm, SIZE UP TRAY.
How can we ensure the full lingual sulcus depth is achieved?
Ask patient to stick tongue UP AND OUT.
2 limitations of stock trays?
- Not made to measure.
- Peripheral extension often OVEREXTENDED (especially posterior).
2 things that can happen if you overfill special trays?
- Excess material can obstruct the airway.
- Prevent full seating of tray.
What can be done to stock trays to improve fit in a PARTIALLY DENTATE PATIENT (free end saddles)?
- Addition of PUTTY.
- Take an impression with the PUTTY.
- Place alginate on top and take ANOTHER IMPRESSION.
What is the thickness of special trays/ the spacing of special trays dependent on?
- Thickness depends on the properties of the impression material to be used.
What are two main reasons for taking impressions in dentistry?
- Construction of appliances.
- Monitoring (pre/post treatment, wear, record keeping).
What are stock trays usually made of?
Metal or MAINLY PLASTIC.
3 things that can happen if you extend denture past palatine fovea?
- Lose seal.
- Patient gags.
- Denture unstable.
4 pros of special trays?
- Accurate peripheral extension.
- Uniform thickness of material.
- Reduces amount of material – less discomfort as tray fits individual mouth.
- Records denture bearing area more accurately.
4 uses of PRIMARY impressions in dentures.
- Treatment planning.
- Construction of special trays.
- Examination of occlusion on articulator (PARTIALS ONLY).
- Surveying - Determination of path of insertion and denture design (PARTIALS ONLY).
How can an overextended stock tray be reduced?
Acrylic bur
What is the advantage of perforated stock trays?
Mechanical retention to keep alginate in tray.
What is the labial frenum?
- Muscle attachment.
- Must RELIEVE around this area.
What can be done if a stock tray is overextended?
If plastic, reduce using an acrylic bur.
What is the disinfection protocol?
- Rinse in running water.
- 2 mins in Articlor (10,000ppm/ 1%) Sodium hypochlorite.
- Remove after 2 mins, run under water with CLEAN GLOVES.
- Cover with damp napkin.
- Label, place in bag, prescription, indicate disinfected.
- Take to laboratory ASAP for casting.
What can be used to modify a stock tray that does not fit well to edentulous areas?
- Putty, red composition.
There is a sharp border at the area of the lingual pouch in the impression. What does this mean?
did not get tongue border molding correct
How short of sulcus depth should special tray extensions be? Why?
2mm, allow border moulding.
We added putty to the stock tray to record edentulous saddles. There are adjacent standing teeth. What must be done?
Use wax knife to cut putty and leave about 3MM CLEARANCE FROM STANDING TEETH.
What must we do after making adjustment to an underextended stock tray using greenstick etc?
- place into the mouth to MOULD MODIFICATIONS.
- Trim putty etc with WAX KNIFE to allow about 3MM CLEARANCE from remaining standing teeth.
Which areas may require prepacking?
High arched palate, tuberosities.
How are special trays made?
Uniform thickness of MODELLING WAX over a STUFY CAST.
- Thickness depends on the properties of the impression material to be used.
what can happen if we dont relieve around the labial frenum?
- can cause soreness.
- denture can catch on frenum and become unstable.
You want to take an impression with silicone elastomers for a complete denture. What is the required spacing/ required wax thickness? What type of complete denture are this appropriate for?
- No spacer.
- Completes - REPLICA.
what is the significance of the hamular notch for dentures?
Common place where dentures dig in.
What is the significance of the mylohoyid ridge for dentures?
It is in the lingual sulcus. Is a lump of bone which can be quite prominent and may give DISCOMFORT under a lower denture.
When is greenstick stops placed around the PERIPHERY of the special tray (2)?
- Tray is not retentive.
- Patient has had problems with LOOSENESS OF AN UPPER DENTURE
What can be used to modify a stock tray that has underextended flanges?
Greenstick/ wax.
What must be done prior to sending primary impressions off to the lab to make a special tray?
DELINEATE using INDELIBLE pencil where you want your tray to end.
What are palatine fovea? What is their significance for denture design?
- Dimples just behind where the hard and soft palate meet.
- Do not want to extend denture over these as you can lose the SEAL, make denture UNSTABLE and cause patient to GAG.
3 advantages of stops on special trays?
- Position tray
- Maintain space for material.
- Allow consistent placing of tray.
4 materials that can be used to modify stock trays?
HIGH VISCOSITY MATERIAL.
- Wax
- Red composition
- Putty
- Greenstick
You want to take an impression with silicone elastomers/ polysulphides. What is the required spacing/ required wax thickness? What types of dentures can this be used with?
- 3mm.
- Partials.
What are the 3 different materials that could be used for special trays? 1 disadvantage of each.
- Light cure acrylic: easy to mold YET very rigid hence hard to remove from model.
- Shellac: brittle and fractures easily YET soften when warmed and thus can be removed.
- Self cure acrylic: problems rolling an even layer.
You want to take an impression with zinc oxide eugenol for a complete denture. What is the required spacing/ required wax thickness? What type of complete denture are this appropriate for?
- No spacer.
- Complete - conventional OR replica.
What are stops for special trays? 3 uses?
- Made of greenstick.
- Placed at POST- DAM AREA + CENTRE OF PALATE, cover in vaseline and put in mouth to mold.
- Position tray
- Maintain space for material.
- Allow consistent placing of tray.
What is the vibrating line?
- Just in front of the palatine fovea, at the JUNCTION OF WHERE THE HARD AND SOFT PALATE MEET.
You want to take an impression with alginate. What is the required spacing/ required wax thickness? What types of dentures can this be used with?
- 3mm.
- Partials and complete.
