RPD Final Impressions (Quiz 4)

Phase IV

Of the 5 phases for the sequence of partial denture treatment, what phase does the following happen in?

- Fabrication and delivery of RPD

- Oral and written instruction

Non-elastic

What type of impression material are the following:

- Rigid materials

- Thermoplastic

Elastomeric

What type of impression material are the following:

- Hydrocolloids

- Polysulfide (Mercaptan Rubber-Base)

- Polyether

- Silicone

- Stock

- Custom trays

Elastomeric hydrocolloids are used in which types of trays?

Irreversible hydrocolloids

Which type of elastomeric impression material has these disadvantages?

- Low tear strength

- Less surface detail

- Not dimensionally stable

- Difficult control of the length and width of impression borders (usually overextended impressions)

Irreversible hydrocolloids

Which type of elastomeric impression material has these advantages?

- Hydrophilic

- Inexpensive

- Pour well with stone

- Pleasant taste and odor

- Custom tray (for uniform thickness)

- Altered cast technique

Elastomeric- mercaptan ruber-base (polysulfide) is used in which types of trays?

Mercaptan ruber-base (Polysulfide)

Which type of elastomeric impression material has these disadvantages?

- Slow recovery from elastic deformation

- Poor long-term dimensional stability (loss of reaction byproduct)

- Unpleasant odor

Mercaptan Ruber-Base (Polysulfide)

Which type of elastomeric impression material has these advantages?

- High tear strength

- Long working and setting time (8-10min) --> better for border molding

- Acceptable accuracy

Polyether impression materials

Which type of elastomeric impression material has these disadvantages?

- Short working and setting time

- Low flexibility, stiffness

- Low tear strength

Polyether impression materials

Which type of elastomeric impression material has these advantages?

- Good accuracy

- Hydrophilic --> good wettability

silicone

Which elastomeric material can be used for all 3 trays (stock tray, custom tray, & altered cast technique)?

silicone

Which type of elastomeric impression material has these advantages?

- High accuracy

- Excellent dimensional stability

- Good tear strength

silicone

Which type of elastomeric impression material has these disadvantages?

- Expensive

- Working time 3-5 min

- Both hydrophilic and hydrophobic

3-5 min

What is the working time of silicone impression material?

silicone

Which impression material is both hydrophillic and hydrophobic?

Accurately record the...

- Remaining teeth

- Full extension and detail of the edentulous area (anterior and posterior)

What are the 2 goals of impressions?

- Pterygohamular notches

- Entire palate

What 2 features of the maxilla are KEY to capture when taking impressions?

1. Buccal shelves

2. Retromolar pads

3. Facial vestibule

4. Lingual vestibule

What are 4 KEY features needed when taking a mandibular impression?

true

T/F: Stock trays can be plastic or metal AND can be perforated or unperforated

retention of impression material

What does perforation of stock trays help with when taking impressions?

Yes

Are plastic trays used with adhesive?

No

Are metal trays used with adhesive?

Metal, plastic

_________ trays are more rigid while _________ trays bend more easily

3-5 mm

The trays needs to cover all the anatomical landmarks. When using a stock tray, how much larger than the outside surface of the residual ridge should it be?

tray too small

Why does this happen when taking impressions?

- The impression material outside of the confines of the tray will be unsupported

- Any area not covered by the tray will not be recorded

- Resulting in under-extended final impression and under-extended RPD

tray too small

What causes under-extended final impressions/under extended RPDs?

tray too big

What causes overextended final impressions?

Rope wax, modeling compound, or heating and opening the plastic/thermoplastic trays

How do you modify a stock tray?

Custom tray

If properly dimensioned stock tray is not possible, what should be fabricated?

When minimal border molding is required:

- Tooth supported cases (Class III and IV)

- Short edentulous areas and minimal bone loss (otherwise, border molding with custom tray is necessary for proper flange extension)

When should you use a stock tray?

true

T/F: A stock tray should be used when minimal border molding is required

stock tray

Which tray can you use for tooth supported cases and short edentulous areas?

III and IV

Stock trays can be used with which kennedy classes?

Alginate

When preparing to place the impression material into the tray, what material can you use for tooth-supported impression?

Border molding movements (should be minimal)

When placing alginate impression material in the oral critical areas (cingulum/occlusal rest seats' preparations), what should you do to best capture the edentulous areas?

- All anatomic landmarks are captured

- Surface areas of major connectors entirely captured

- All aspects of abutment teeth were recorded (rest seats, lingual and buccal aspects where reciprocal and retentive arms will be located)

When you remove an alginate impression, what should you look for when assess the quality?

Type V

After taking an alginate impression, you should disinfect and pour the impression immediately with what type of dental stone?

Store in 100% humidity and pour within 30-60 minutes

If you cannot pour alginate immediately, how can you store it?

tooth supported

Tooth supported or tissue supported impression?

- Taken at rest

tissue supported

Tooth supported or tissue supported impression?

- Impression taken in function

tooth supported

Tooth supported or tissue supported impression?

- Taken with no pressure

tissue supported

Tooth supported or tissue supported impression?

- Impression taken under pressure

tooth supported

Tooth supported or tissue supported impression?

- Taken with minimum support

tissue supported

Tooth supported or tissue supported impression?

- Taken with maximum support

tooth supported

Tooth supported or tissue supported impression?

- More movement can lead to loose abutments

tissue supported

Tooth supported or tissue supported impression?

- Overly displaced tissue can become inflamed, impaired accompanied with bone resorption

tooth supported

Tooth supported or tissue supported impression?

alginate can be used

true

T/F with stock trays, border molding movements are done but should be minimal

- Anatomy (presence of tori)

- Need border molding

What 2 reasons would you use a custom tray over a stock tray?

custom tray

When you have a class IV case where the flange is necessary to compensate for bone resorption, or tissue supported situations, which tray would you use for impressions?

stock tray

Stock tray or custom tray?

- Less lab time

custom tray

Stock tray or custom tray?

- More lab time

stock tray

Stock tray or custom tray?

- Less accurate

custom tray

Stock tray or custom tray?

- More accurate

custom tray

Stock tray or custom tray?

- Have anatomical limitations

1. Draw a line at the depth of the vestibule

2. Draw the outline of the custom tray; 2 mm short of the depth of the vestibule

3. Draw the outline of the spacer; 2 mm short of the outline of the tray. (4mm shorter than the depth of the vestibule)

What 3 areas do you draw to outline the tray on a maxilla?

2mm

How many mm short of the depth of the vestibule is the custom tray when drawing the outline?

4mm

How many mm short of the depth of the vestibule is the wax spacer when drawing the outline?

Wax spacer

ID the outline in blue:

Custom tray

ID the outline in red:

Vestibule

ID the outline in green:

block undercuts and add wax spacer

When making a custom tray, once vaseline is applied and the cast is outlined, what is the next step?

4 mm short of depth of vestibule

When trimming excess of the baseplate wax, how much space should the wax spacer be from the vestibule?

Wax should be a little short of the line connecting the pterygo-maxillary notches

When trimming excess of the baseplate wax, how much space should the maxillary triad be from the posterior?

Yes, 1-2 additional layers

When making the custom tray, should you add extra layers of wax over teeth?

2x2 windows

What do you add to the areas where there are teeth before curing the triad to create vertical stops + maintain space for the impression material?

aluminum foil

Once the triad is complete but not cured, what do you place over the teeth areas once windows are made?

more triad

What do you fill the 2x2 windows with before curing?

- 1-2 minutes

- Turn tray over to cure intaligo for another 1-2 minutes

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

- Final cure for about 4-5 minutes, total = 6-7 min

How long do you cure the triad tray for?

False - 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.

T/F: Remove all the wax on the cured triad for border molding

2mm

How much shorter is the triad once cured, from the vestibule?

- Buccal shelf

- Retromolar pad

What are the primary bearing areas of the mandible?

- Contour and quality of residual ridge (secondary bearing areas, firm/dense soft tissue, round ridge form)

- Denture base coverage (broader=better)

- RPD design (rest location)

- Type and accuracy of impression (viscosity of impression material, rigidity of trays, impression techniques)

- Occlusal load applied (depends on number of artificial teeth, width of occlusal tables)

- Fit of the denture base (intimate contact between intaligo of denture base and residual ridge)

What are factors influencing support of distal extension base?

Distal to mesial

For the RPD design to support distal extension base in altered cast technique, the rests are moved from _________ to _________

I and II (mandibular distal extension)

The altered cast technique is recommended for which classes on the mandible?

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

What is the purpose of the altered cast technique (also called dual technique)?

altered cast technique

These are advantages of which impression tray technique?

- Improves fit of the denture bases

- Reduces the number of postoperative visits

- Preserves the residual ridges

- Improves stress distribution

true

T/F: The metal framework is required back from the lab in order to perform the altered cast technique

1. Apply triad to metal

2. Do border molding in new custom tray

What are the first 2 steps when using the altered cast technique once the metal framework is tried in the patients mouth?

Stock

What final impression technique is used for the blue colored images?

Custom

What final impression technique is used for the green colored images?

Altered cast technique

What final impression technique is used for the red colored images?

2-3mm

Once triad is added to the metal framework for the altered cast technique, the acrylic should be ___-___ mm short of the buccal vestibule

buccal frenum and shelf

Which structure is captured with border molding with these actions?

Cheek is:

- Elevated

- Pulled downward

- Pulled outward

- Pulled inward

- Pulled forward for the action of the orbicularis oris

- Pulled backward for the action of the buccinator

masseteric notch

Which structure is captured with border molding with these actions?

- Hold down the framework and instruct the patient to close his mouth hence contracting the masseteric muscle.

retromolar pad

Which structure is captured with border molding with these actions?

- Patient opens his mouth as wide as possible

mylohyoid area

Which structure is captured with border molding with these actions?

- Tongue touching the cheeks

retromylohyoid fossa

Which structure is captured with border molding with these actions?

- Ask patient to move his/her tongue forward

attach to cast (cast has cutout portion where border molding was completed)

Once border molding is done on the metal framework, what do you do with the metal framework now?

Polysulfide

What impression material is mixed and loaded into the distal extension on an altered cast technique?

roping wax

What do you attach to the impression once it is mounted back on the cast?

2-3 mm

Roping wax should be ___-___ mm above the border molding impression

3-5 mm

Roping wax should be ___-___ mm wide for land area around the border molding impression

more than 2 rows

How many rows of roping wax are necessary for the retromolar pad area?

boxing

What type of wax is added around the cast once roping wax is added?

Pour type III dental stone

What is the last step once boxing wax is set up?

Fill with cold curing resin

Check the fit of the tissue stops. If there is space under the tissue stop, what should you do?

true

T/F: The altered cast technique provided the least amount of movement from the occlusal loading at the time.

true

T/F: In a one piece cast, underextension was noted in 22% of cases but no underextension was found in the altered cast impression procedure