lab 5- tooth modification

Question 1

Why might we need to modify teeth

Answer 1

1. Create space for occlusal rests
2. Create undercuts where none exists
3. Block out undercut where it is inconvenient
4. Create guide planes

Question 2

Why might we need to create space for occlusal rests

Answer 2

so that they don’t cause an interference to the bite

Question 3

How can we create undercuts on a tooth

Answer 3

By adding composite

Question 4

What is another name for secondary impressions

Answer 4

Major or working impressions

Question 5

What are the aims of a secondary impression

Answer 5

1. Accurately record the denture bearing area
2. Record the functional depth and acceptable width of the sulk where a denture flange or major connector will extend
3. Record the abutment teeth and tooth preparation in sufficient detail

Question 6

What are secondary impressions taken with

Answer 6

A special tray

Medium and light bodied silicone or alginate

Question 7

When would we use alginate to take a secondary impression

Answer 7

When there a lone tooth standing

Question 8

Which material is more accurate: silicone or alginate?

Answer 8

Silicone

Question 9

Which material do technicians prefer: silicone or alginate? Why

Answer 9

Alginate as it is easier to remove off the tray and is harder to break

Question 10

What are some qualities of special trays

Answer 10

1. They extend 2mm short of the sulcus depth
2. 3mm space where there are teeth
3. Is close fitted in edentulous areas
4. Has stops

Question 11

Why do special trays need to extend 2mm short of the sulcus depth

Answer 11

To allow space to add greens tick for border moulding

Question 12

Why do we have stops on special trays

Answer 12

To create space and ensure the impression material is of even depth the whole way round the mouth

Question 13

Where do we want stops to be on partial dentures

Answer 13

On teeth

Question 14

Describe how we create a special tray

Answer 14

1. Put tray in position in the patients mouth
2. Carry out muscle trimming and see if there are any over extensions
3. Use greens tick or heavy bodied silicone on borders of tray
4. Trim border material from inside of tray
5. Apply adhesion
6. Take final impression in silicone or alginate

Question 15

When would you add green stick to a special tray

Answer 15

Only needs to be placed in areas where we are putting components onto the denture eg flanges or gingival ally approaching clasps

Question 16

Name the step we need to carry out to ensure we take a good prosthetic impression

Answer 16

Border moulding

Question 17

Why is border moulding important

Answer 17

To record the functional sulcus for correct flange extension and major connector position

Question 18

What can we use to carry out border moulding

Answer 18

1. Green stick

2. Heavy bodied silicone

Question 19

How to we carry out border moulding using green stick

Answer 19

1. Set Bunsen burner and
   warm water bath
2. Heat green stick in fire by constantly moving it and waiting for it to droop
3. Drape the green stick onto the borders staying more to the outside of the tray
4. Always insert the tray into warm water for a couple of seconds before putting it into the patients mouth
5. Trim any excess
6. Remove excess impression compound from the fitting surface with a hot wax knife

Question 20

Why should we place the impression tray into warm water before placing it into the patients mouth?

Answer 20

To cool the impression down a little so it doesn’t burn the patient

Question 21

How should the impression compound look after you have placed it into the mouth

Answer 21

The impression compound must look as if it has moulded to the shape of the sulcus
You should be able to see the depth and buccal surface

Question 22

How should we get rid of folds and voids on an impression

Answer 22

By muscle trimming after re heating the compound

Question 23

What is a perforation on a special tray

Answer 23

Holes greater than 2mm in diameter

Question 24

When are perforations needed on a special tray

Answer 24

When using alginate

Question 25

Why do we need to put perforations on a special tray when using alginate?

Answer 25

To reduce the impression pressure

Question 26

What happens if you need perforations on a special tray but have forgotten to ask for them

Answer 26

You can create perforations chair side using a rose head burr in a straight handpick

Question 27

What can be a potential problem if you make a special tray with perforations

Answer 27

Perforations reduce impression pressure unevenly which can cause a potential theoretical problem for imps of mucosa

Question 28

What is the preferred material for definitive secondary impression

Answer 28

Medium bodied silicone with a light bodied silicone wash

Question 29

How do we use medium bodied silicone

Answer 29

1. Block out any visible embrasures with carding wax
2. Light bodied silicone is then syringed intra orally onto any tooth surface the cobalt chrome will touch
3. Tell you assistant to full the special tray with medium bodied silicone
4. Insert position and seat the filled tray into the patients mouth
5. Border mould the soft tissues until the silicone sets

Question 30

How do we tell the technician how much we want to trim the model

Answer 30

Draw a line 2mm from the depth on the outside of the impression to guide the technician when trimming models