(1a) Preliminary Edentulous Impressions

What are the five clinical appointments when making a denture for a patient

1. Diagnostic Information

2. Final Impression

3. Jaw relation record

4. Wax try in

5. Denture delivery

What occurs during the first diagnostic appointment

- Take note of all edentulous anatomy

- Take alginate impression

- Fabricate custom tray

What occurs during the second final impression appointment

- Border molding

- Final Impression

- Box and Pouring master cast

What is border molding?

shaping of the border areas of an impression material by functional or manual manipulation of the soft tissue adjacent to the borders to duplicate the contour and size of the vestibule while functioning

What occurs during the third jaw relation record appointment

- Record Base, occlusal rim

- Articular and Facebow

- Maxillomandibular relationship (MMR)

What occurs during the fourth wax try in appointment

- Denture esthetic, setting anterior teeth

- Denture Occlusion

- Setting posterior teeth

- Waxing and Festooning, posterior palatal seal

What occurs during the fifth denture delivery appointment

- Denture insertion, adjustments

What is the purpose of the preliminary edentulous impressions

To fabricate the diagnostic casts

What are the diagnostic casts used for?

To fabricate the custom trays

What is the preliminary edentulous impressions made out of

Alginate

Why do we need to fabricate custom trays

- Required to accurately register moveable mucosa

- Provides the ability to create seal for retention

The alginate impression is a ______ mold, and the diagnostic cast is the ______ mold

Negative, positive

Once you take the alginate impression what should you be looking for?

Look at our impression to make sure you captured all of the proper anatomy that is needed.

If you did not then you need to retake the impression

What trays are used to take the preliminary edentulous impressions

Stock trays

What should you do if the stock tray does not extend far enough

Use rope wax to extend the tray in order to capture as much anatomy as possible

What trays can you absolutely not use for alginate preliminary impressions and why

Massad trays because the material is thermoplastic

Why is the purpose of a massad tray

Since they are thermoplastic you can put them in hot water and mold it to the patients mouth and take a final impressions with them. This allows you to skip one whole appointment but when you are skipping a step it is more technique sensitive!

What are the trays that we have in preclinic

COE Spacer stock trays

What should you apply to the stock tray before taking the preliminary impressions

Alginate adhesive

Why do we need to place alginate adhesive in the tray

It makes sure that the material stays in the tray because if the material detaches from the tray at all the material can get distorted which distorts every step after that

What is the goal of the preliminary impression

To obtain an over extended impression of the edentulous foundation area and adjacent tissues recording all accessible landmarks

What are the two main components of alginate powder

Diatomaceous earth

Sodium phosphate

Diatomaceous earth is the _______ and sodium phosphate is the _______

Filler, Retarder

diamaceous earth makes up _____% of alginate powder

60%

T/F The setting time of alginate can be altered

True

How can the setting time of alginate be altered

By changing the water powder ratio or mixing time or temperature of the water

What happens to the setting time of alginate if you increase the water temperature

It sets quicker

What happens to the setting time of alginate if you decrease the water temperature

It sets slower

T/F Due to changes in setting time it is important to always work in a cooler environment because if you are working in a warmer environment it will decrease the setting time and materials will set quicker

True

If you need to work in a warm environment what can you do to solve the issue of the material possibly setting to quickly

Use ice water

There is _____ reduction in setting time for each ______ increase in temperature

One minute, 10 degrees Celsius (18 F)

What is the favorable method to increase setting time if regular set is not available

Altering the water temperature

What can happen if you alter the setting time of alginate

It may alter the dimensional stability of the impression

How is setting time BEST regulated for alginate

By differing the amount of retarder (sodium phosphate) in the powder

What are the two forms of alginate made by the manufactuer in regards to setting time

Regular set and fast set

fast set alginate sets _____ as quick as regular set

2x

What does alginate have a tendency to do after it sets

Lose or absorb water

What is losing water called

Syneresis

** will be a question of the exam

What is absorbing water called

Imbibition

** will be a question of the exam

What will happen to alginate if the storing conditions are dry

It will lose water and shrink

What will happen to alginate if the storing conditions are really wet

It will absorb water and swell

What should you do to store our alginate properly after taking the impression

Wrap in in a damp paper towel and place it in a plastic bag

What are two ways that alginate can come in

Pre-weighed pouches

Bulk material

Only need to measure water

What are the benefits of using alginate in preweighed pouches

Easier dispensing

Minimizes contamination

What is the disadvantage of using alginate in preweighed pouches

More expensive

What can cause the bulk alginate material to deteriorate

Stored above 54 degrees Celsius (129.2 F)

Repeated opening of container

What does the deterioration of bulk alginate result in

Thin mixtures

Reduced strength

Permanent deformation

What is the scientific name for alginate

Irreversible hydrocolloid

How should you scoop alginate powder

- Fluff the powder

- Scoop then tap and flatten the scoop

How many alginate scoops should be used for stock tray impressions

3 scoops

How much water should you use for 3 scoops of powder

Water to the 3rd line

When mixing alginate should you add the water or the powder first

Add the water to the bowl first and then add the powder

What consistency are you aiming for to achieve when mixing alginate

Dough like consistency

(Should not look spongy and be granular or lumpy)

How does Dr. Su go about mixing alginate

She pours half of the water into the bowl first then pours the powder and starts to mix and if it is too dry she slows add the rest of the water into the mix until she reaches a smooth dough like consistency

Why is it important to add powder into liquid in the alginate mixing bowl especially when mixing fasts set alginate impression material

To ensure complete wetting of powder particles. If the powder is placed first in the mixing bowl, penetration of the water to the bottom of the bowl is inhibited and greater mixing time may be required to ensure a homogenous mixture

How should you mix the alginate to ensure every granule of powder gets mixed

Smash the spatula against the bowl and rotate the bowl at the same time. Do not just mix in the middle of the bowl.

How do you load the tray with alginate

You scoop the material up using the spatula and scrap it into the tray.

What should you do with the remaining alginate in the bowl after loading the tray and the before you place the tray in the patients mouth

You should take the remaining alginate and use your finger to put it in the vestibule and on the palate

What should you use to retract the cheeks/lips when placing the tray if you need to

An intraoral mirror (never use finger)

How should the patients head be when placing the tray into the patients mouth

Should be tilted forward so the material does not flow back

Which arch does Su usually impress first

The mandibular arch because it is easier and it eases the patient into the process

(Ask patient to lift up their tongue)

How should you go about placing the tray into the patients mouth

Place one side in and then the other because no patients mouth is wide enough to place it all in at once

Where rope wax is usually placed on stock tray

What should you do if a patient has large tori or too large of ridges for the stock trays

Trim the tray or add green compound of heat up the stock tray and adjust it. (Place in cold water before placing it in the patients mouth)

Now we are going into the evaluation of the preliminary impression evaluation criteria

Ok

What is the preliminary impression evaluation criteria

- All detail is reproduced, including the peripheral roll and the retro molar pads or tuberosities

- Detail is sharp, not blurred or indistinct

- Free of void in critical areas

- Free of large folds of alginate

- No areas where alginate has pulled away from the tray (avoid by adding adhesive)

- Free of rips or tears

- Alginate thoroughly covers the tray, no tray visible through the alginate

- Free of bulked areas or depressions

- Alginate is smooth, not sponge like

Now we are going into the gypsum stone

Ok

What is the gypsum powder

calcium sulfate hemihydrate

How should you measure the water to gypsum powder ratio

Always use the manufacturer specifications and measure mL of water and weigh g of powder

What can be added during mixing gypsum and water to facilitate the mixing and pouring process

Extra water

What can occur if the water to powder ratio of gypsum stone mixing increases

- Setting time increases

- Flow of mixture increases

- Setting expansion decreases

- Compressive strength decreases

What are the steps to obtain a Dx cast

1. An alginate impression is made directly in the mouth of the patient producing a negative mold

2. The impression is poured in dental stone, producing a positive cast

3. The cast in inspected for defects, repaired if possible and trimmed to the proper size and shape on a model trimmer

What are the steps of pouring up the Dx cast

1. Weigh powder and measure water

2. Vacuum mix

3. Flow stone into alginate impression from one end

4. Modulate speed of pouring by tilting back and forth, or pressing the tray firmly into the vibrator

If you vacuum mix for less time the strength of the cast _______

Increase

How should you pour the stone into the alginate cast

Pour from one end to another making sure it flows into all the necessary areas. Periodically use the vibrating plate to allow the air bubbles to come to the surface

T/F When pouring the stone into the alginate impression it should always be on the vibrating plate

False: it should be placed on there periodically

What should you do if you see any bubbles while pouring up the cast

Remove the bubble using a smaller instrument

What are the two types of techniques for pouring up your diagnostic case

One pour or two pour

what is the two pour technique?

mix stone and flow into alginate impression from one end to the other, allow to thicken for a couple of seconds before flipping it upside down onto a pile of more stone

The pad of stone in the two pour technique should be _______ so it is more stable and does not flatten

Vicious

How long should you wait until you remove the alginate impression from the stone cast

Ideally 45 minutes after but max 2-3 hours

Now we are going into trimming the stone

Ok

The casts should be a minimum of ______ in the thinnest part

10-15mm

Seperate the alginate impression from the stone cast after _______

45 minutes

The base should be trimmed _____ to the residual ridges

Parallel