Partial denture 4 Flashcards by Jasmin d

What is the aim of primary impressions

Create cast for further denture construction work
Design denture
Surveying the teeth
Using general treatment planning to decide which teeth will need to be replaced
Special tray - impression tray
We need impression to cover entire denture area
Accurate impression of all standing teeth and buccal and lingual surfaces

How well did you know this?

Not at all

Perfectly

what are the arrows representing

Indication of full denture bearing area
Upper arch - whole of hard palate
Vibrating
Good impression of any sulcus areas where teeth are missing
No posterior teeth
Good recording of maxillary tube veracity

How well did you know this?

Not at all

Perfectly

what are the arrows representing

Lower arch - no palate - record well any areas where teeth are missing
Record sulcus areas buccally
Good impression of lingual sulcus all the way round
No posterior teeth - extend impression all the way around
Retomolar pad- thickened area of mucosa

How well did you know this?

Not at all

Perfectly

What are the problems with the retromolar pad

Sometimes retromolar pad isn’t easy to see
Should be in these regions
Can’t sometimes see retromolar pad
Impressions of models show the retromolar pad

How well did you know this?

Not at all

Perfectly

Name different types of elastic impression materials

How well did you know this?

Not at all

Perfectly

Name different types of inelastic impression materials

How well did you know this?

Not at all

Perfectly

what do we consider when taking a impression of objects with undercuts

Elastic material - needs to cover teeth with undercut area and interproximal spaces

Elastic material able to come out of those areas and spring back to shape

How well did you know this?

Not at all

Perfectly

How are primary impressions usually taken

How well did you know this?

Not at all

Perfectly

Describe the chemicals aliginate contains

Irreversible hydrocolloid
Don’t need to learn chemical processes
Just need to be aware of what material it contains

How well did you know this?

Not at all

Perfectly

What are the advantages of alginate

Well tolerated- too hot or cold
Add flavours to it
Flows well over the surface
Mucostatic- doesn’t distort tissues too much

How well did you know this?

Not at all

Perfectly

What are the disadvantages of alginate

If left open to atmosphere - will dry out
syneresis= long polysaccharide chains in alginate material will coil up and squeeze water out
Seal in plastic bag
Swells up in water - through process call imbibition
Poor tear resistance - might tear when taking impression back out
Require adhesive to stick to impression tray

How well did you know this?

Not at all

Perfectly

what are the 4 stages in impression taking

Modify with various materials
Alginate needs to be supported by rigid
Put adhesive on tray
Check impression to make sure it fulfils requirement

How well did you know this?

Not at all

Perfectly

How do we select trays

Select try
Usually medium and see if it goes over teeth and hope to see couple mm of space on either side
Should cover all teeth
Teeth behind impression tray
Should extend to short of 2 mm

How well did you know this?

Not at all

Perfectly

What are the common problems of selecting trays

How well did you know this?

Not at all

Perfectly

Why is tray modification needed

May need to add material if short of sulcus depth
If excessive amount of spaced between tray and mucosa

How well did you know this?

Not at all

Perfectly

name the problem and how to modify

tray is short of sulcus depth
Alginate material may get there but would be unsupported and floppy
Avoid any parts of impression where the alginate might be sticking up without being supported

How well did you know this?

Not at all

Perfectly

3 materials used to modify tray to make it more suitable to take impression for partial dentures

How well did you know this?

Not at all

Perfectly

Describe this

Larger edentulous areas, big bulk of alginate unsupported
Large height of alginate material - like a gel - take a impression of it and tend to slump in the area afterwards

How well did you know this?

Not at all

Perfectly

Describe this

Modify tray by adding material in the area to take up some of the space
Silicone putty or wax
Alginate is now supported

How well did you know this?

Not at all

Perfectly

what do you need to make sure when taking impressions and alginate

Load tray with alginate making sure it completely covers entire tray

How well did you know this?

Not at all

Perfectly

How do we position when taking lower impressions from a patient

Stand in front of patient
Patient mouth about level with elbows

How do we position when taking upper impression from the patient

Stand behind patient- chair leaning back slightly
Mouth adjusted so same height as elbow
Upper impression in front - end up having to stoop down - twist spine or hurt back

Describe border moulding labial and lingually

While the impression material is soft - stimulate normal function of the mouth

Ask patient to move tongue around

Tongue into one cheek or the other

How do we assess completed impressions

what is the issue with this impression

Same patient on same day 1st impression Okay impression of teeth but massively underdeveloped edentulous area Make sure teeth are fine and covered entire denture bearing area

How do we mark the extent for special tray

Once happy with an impression Draw a line 2mm short of incisal Technician makes plaster model - the line will come out on that model

what are the aims of SECONDARY IMPRESSIONS

What are the stages of secondary impressions

Greenstick Take impression - alginate or silicone Rest / impression needs to be accurate Fits snugly into that seat Clasps need to be in a undercut area - esp cobalt chrome 2.2.5 mm depth Sometimes teeth don't have a natural undercut Changing the survey lines Survey lines higher up

What additive techniques can we use to modify the secondary impression

Anterior Cingulum rest Much more likely to create a flat surface to create a rest seat for us

What are special trays

Made specifically for a patient So they fit the patient's mouth

Describe the special trays specification

Using alginate Need a spec fo 3mm around teeth to be flexible Large edentulous areas- no undercuts there Get trayed without any space- close fitting Special tray to be within 2 mm of full depth beneath sulcus

How do you perforate special trays

Ideal 3mm space between trya and tooth in all dimensions Push it down too far and loose the space occlusally

Lost the space Once we pushed it too hard

Include stops within the special tray Raised areas of acrylic that rest on the teeth 3 mm above teeth all the way around

What are stops

Little bits of acrylic / greenstick to a tray to prep the tray up

What is special trays - border moulding

describe the sulcus at rest and sulcus during function

Displace denture Need to do impression of functional depth of width of the sulcus

Describe the clinical technique of border moulding

1. Set up warm water bath (50 degrees) Impression compound comes as pink or green stick - pink stays softer for longer (thermoplastic materials) 2. Keep moving the impression compound in and out of the flame for a few seconds each time until it starts to droop. Drape it onto the tray border staying more to the outside for eh tray. The tray must be dry for it to stick. 3. Always insert into warm water for a couple of seconds before putting it into patients mouth otherwise can cause a burn 4. The impression compound must look as if it has moulded to the shape of the sulcus, Folds and voids should be eliminated by further muscle trimming after re heating the compound 5. Finally excess impression compound must be removed form the fitting surface with a hot wax knife, leaving only the depth and buccal surface remaining,

What do we need to be aware of inside the tray

What would happen if we left green stick to pink stick inside of tray Area of impression material , when we remove has to squeeze through space Compressed Spring back to original shape Area know squeeze through is less

Hw would you remove green stick from inside of tray

Remove greenstick or pink stick on inside of tray But still record depth and width of sulcus Apply adhesive to tray Take our final impression Draw line on outside of tray - 2mm form depth to guide technicion when trimming model. Make sure no damage is done to flanges Impression fro complete denture

what occurs after all impression taking

What do we need to check when trying in metal framework

How do we check the accuracy of fit of the components

also check the position of the retentive and bracing arm - Inspect all components which are designed to be clear of the gingival margin area, and check that the clearance is adequate - Check the stability of the framework -Finally check the occlusion for clearance of all components

How do we examine the framework in the mouth

- If upper and lower frameworks are to be tried in, try each independently - Check the occlusion of each separately and then together to ensure that there are no premature contacts. This should be done by visual examination, comments from the patient and the use of articulating paper or occlusal indicator wax - Adjusting the framework disclosing paste used to determine areas of metal work that need adjustment to aid seating

What does recording the occlusion mean

Using wax blocks in patient mouth Close together and trim those blocks Learn more in practice

What are we trying to achieve at this clinical visit

What do we have to do after recording the occlusion: 3 scenarios -

Look at lectures for case

What can be used to record the patients occlusion

Blue mousse - pick up impression of opposing teeth