2. final impressions part 2

what are the first eight steps of fabricating custom trays for maxillary impressions?

1. apply vaseline as a separating medium on trimmed prelim cast

2. outline the tray (3 lines: vestibule, tray, wax spacer)

3. add wax spacer

4. cut off excess

5. add extra wax layers over teeth

6. prepare windows through wax on top of teeth 

7. place aluminum foil 

8. fill windows with triad

what are the three lines drawn for tray outline?

• one at depth of vestibule

• one outline of custom tray 2mm short of vestibule

• one outline of wax spacer 2mm short of tray outline (optional)

*maxilla and mandible

explain the selective pressure method of outline of wax spacer

short at retromolar pad and buccal shelf area, putting pressure in primary bearing areas and relieve others

what type of wax is used for wax spacer?

baseplate wax

T or F: teeth indentations should not be visible in tray otherwise tray will sit in cast but not mouth

true

excess wax spacer should be trimmed with a (BLANK 1) and follow the outlines drawn (BLANK 2)mm from the depth of the vestibule. posteriorly the wax should be a little short of the lines connecting the (BLANK 3)

• BLANK 1: 15 blade wax instrument

• BLANK 2: 4mm

• BLANK 3: pterygo-maxillary notches

how big are the windows for maxillary custom tray impressions?

(4) 2 × 2 mm

maintain vertical stop maintaining space for impression material to be filled by traid 

is it necessary to place aluminum foil?

no

over teeth only as separator (wax from tray) and create windows that will be filled with traid to create a stopper 

what are steps 9 -15 of fabricating custom trays for the maxilla?

9. Place Triad tray material over the wax

10. Trim off the excess material using #15 scalpel or a sharp instrument along the outline

11. Attach a handle using the excess Triad material or a metal handle

12. Cure tray for about 1 to 2 minutes

13. Turn tray over to cure intaglio for another 1 to 2 minutes

14. Tray should be cooled by running water from time to time in order to avoid wax melting

15. Final cure for about 4 – 5 minutes.

what are the final two steps of fabricating custom trays for the maxilla?

16. trim excess a the borders and smooth any sharpness (add grooves to improve grip)

17. Remove the wax and aluminum foil only on the teeth. The rest of the wax should be maintained during border molding and removed only before taking final impression.

what are the first six steps of fabricating custom trays for mandible?

1. start w properly trimmed diagnostic cast

2. outline tray w three lines 

3. blockout undercuts with baseplate wax

4. apply vaseline as separating medium 

5. cut a piece of baseplate wax into two strips (spacer)

6. soften and place one strip on one side then soften and place the other strip on the other side

what are steps 7-10 of fabricating custom trays for mandible?

7. trim back wax over primary bearing areas: buccal shelf and retromolar pad

8. add two layers of wax over teeth not on primary bearing areas still!

9. prepare three windows through wax over teeth evenly distributed across midline

   1. these windows will be filled w triad to create vertical stops maintaining space for the impression material

   2. (3) 2 × 2mm

10. place aluminum foil over teeth as separator, then open windows created 

what steps do mandible and maxilla have in common?

11-16

11. Turn tray over to cure intaglio for another 1 to 2 minutes

12. Tray should be cooled by running water from time to time in order to avoid wax melting

13. Final cure for about 4 – 5 minutes

14. Tray should be cooled by running water from time to time in order to avoid wax melting

15. Final cure for about 4 – 5 minutes.

16. trim excess a the borders and smooth any sharpness (add grooves to improve grip

what is the last step of fabricating custom trays for mandible?

17. remove the wax and aluminum foil only on the teeth; the rest of the wax should be maintained during border molding and removed only before taking final impression

what does the altered cast technique help with?

getting more support from edentulous areas 

what are the six factors influencing support of the distal extension base?

1. contour and quality of residual ridge

2. denture base coverage

3. RPD design

4. type and accuracy of impression*

5. occlusal load applied

6. fit of denture base

which of the six factors influencing support of the distal extension base?

• maxillary and mandibular secondary bearing areas

• firm and dense soft tissue

• round ridge form (vs knife edge)

contour and quality of residual ridge

which of the six factors influencing support of the distal extension base?

• the broader the better

denture base coverage

which of the six factors influencing support of the distal extension base?

• rest are moved from distal to mesial (A → B)

rpd design

which of the six factors influencing support of the distal extension base?

• viscosity of impression materials

• rigidity of impression trays

• impression techniques

type and accuracy of impression

which of the six factors influencing support of the distal extension base?

• depends on number of artificial teeth (C vs D)

• depends on width of occlusal tables

occlusal load applied

which of the six factors influencing support of the distal extension base?

• intimate contact btwn intaglio of denture base and residual ridge

fit of denture base

another name for altered cast technique

dual technique

which technique?

• Introduced in 1937 by Dr. Applegate

• Was coined as altered cast technique by Dr. Holmes in 1965

• Recommended for mandibular distal extension (Class I and II)

• Purpose: to capture the residual ridges in their functional form and in relation to the remaining teeth

• Advantages: improves fit of the denture bases, reduces the number of postoperative visits, preserves the residual ridges and improves stress distribution

altered cast techniques

what is the purpose of the altered cast technique?

to capture the residual ridges in their functional form and in relation to the remaining teeth

describe the altered cast technique steps

• The framework is obtained from the lab and tried-in

• Acrylic is added to the framework, border molding is performed, and the final impression is taken

• The new impression is boxed to obtain the master cast

which technique?

altered cast

metal framework on initial case then fabricate a custom tray on top of metal framework for edentulous areas. use this custom tray to do border molding in mouth and take final impression. 

4: cut eden areas and create notches for retention

5: metal framework w new impression

6: box and pour

7: final combined case with teeth from initial cast and edentulous areas from second impression

internet definition: corrects inaccuracies in the initial cast of a distal extension area, ensuring better fit, stability, and support for the denture base under functional load. The process involves creating a final impression of the edentulous ridge using a separate baseplate on the RPD framework, sectioning the original cast in the saddle area, and then re-pouring the sectioned part with a new stone to create an altered, more accurate cast

altered cast technique is indicated for which kenn classes?

mandibular class I and II

combined cast made of

teeth from initial cast and edentulous areas from second impression

what steps are added with the clinical visits with the altered cast technique?

at second visit: add acrylic t distal extension (lab) and border molding/final impression

between second and third visit: pour impression and record bae and wax rim

what are the first 10 steps of the altered cast technique impression?

1. block out undercuts with wax

2. draw the outlines: dentures and tray (vestibule. tray, wax spacer)

3. apply separating medium

4. seat metal framework on cast

5. apply resin tray material (traid) to metal struts or mesh

6. trim material'

7. after polymerization, trim border w lab bur and arbor band

8. adjust extensions/acrylic borders intra-orally

9. border mold tray with compound: structures to be captured and associated border molding movements

10. remove excess modeling compound in intaglio surface

which step?

• Buccal shelf area: acrylic should be 2-3mm short of the buccal vestibule

  • Assess by moving cheek up/ down / forward/ backward/ in/ out.

• Cover retromolar pad

• Disto-lingual extension: ask patient to move his/her tongue forward Lingual extension: tongue touching the cheeks

step 8 Adjust the extensions/ acrylic borders intra-orally

which structure for border molding?

cheek is elevated, pulled down, out, in, forward for orbicularis oris, back for bucinator

buccal frenum and buccal shelf

which structure for border molding?

hold down the framework and instruct the patient to close their mouth hence contracting the masseter muscle

masseteric notch

which structure for border molding?

patient opens mouth as wide as possible

retromolar pad

which structure for border molding?

tongue touching the cheeks

mylohyoid area

which structure for border molding?

ask patient to move his/her tongue forward

retromylohyoid fossa

which steps of altered cast technique impression?

11. distal extension should be dried w gauze and adhesive should be applied

12. impression material (here polysulfide) is mixed and loaded onto the distal extension 

last two steps of altered cast technique impression?

13. Seat the framework intra-orally

    1. Make sure it is properly seated (look at rest seats)

    2. As the impression material is setting, redo border molding movements

14. examine impression make sure no voids or inaccuracies

first five steps of cast fabrication (impression major step one and fabrication is major step 3.2)

1. Cut off distal extensions from the cast you used to fabricate the metal framework 

2. Put some retention notches and seat back framework on the cast

3. secure framework on cast with sticky wax

4. attach roping wax at periphery of impression for boxing 

5. adding boxing wax around cast and impression

arrows

retention notches of step 2 of fabrication of cast

what are the three requirements of wax for step 4 of altered cast fabrication of cast: attach roping wax at periphery of impression for boxing?

1. wax should be 3mm above the impression border

2. roping wax should be 5 mm wide for land area

3. more than 2 rows of roping wax are necessary for retromolar pad area

step 4 altered cast fabrication of cast:

wax should be (BLANK)mm above impression border

3mm

step 4 altered cast fabrication of cast:

roping wax should be (BLANK)mm wide for land area

5mm

step 4 altered cast fabrication of cast:

more than (BLANK) rows of roping wax are necessary for retromolar pad area

2

what step of altered cast fabrication of cast?

5

steps 6-11 of step 4 altered cast fabrication of cast:

6. pour w dental stone type III

7. remove wa and soak cast in warm water to soften modeling compourn

8. remove the framework carefully from the cast

9. flame the trias and remove it from the framework

10. clean up the metal framework and put it back on the cast (sometimes space under tissue stop)

11. check the fit of the tissue stops. If there is space it should be filled w cold curing resin (GC pattern)

the altered cast technique provided the (most/least) amount of movement from the occlusal loading at the time

least

under extension was noted in (BLANK)% of the one-piece cas and none of the altered cast impression procedure, no other difference was found

22%