PARTIAL DENT - Prosthodontics Impressions

Question 1

what is important to record when taking impressions for pros?

Answer 1

full extend of the denture bearing area
the functional depth of the sulcus

Question 2

what muscles change the shape of the buccal sulcus?

Answer 2

the buccinator and incisive muscles

Question 3

what are the 6 key anatomical features of the lower denture bearing area?

Answer 3

buccal sulcus
lingual sulcus
mylohyoid ridge
pear shaped pad
retromolar pad
buccal shelf

Question 4

what is the buccal sulcus?

Answer 4

the depression between the cheek and alveolar process

Question 5

define lingual sulcus

Answer 5

the depression between the tongue and alveolar process

Question 6

define buccal shelf

Answer 6

the bony structure located on the posterior lateral area of the mandible

buccal to the alveolar ridge

Question 7

where is the pear shaped pad and the retromolar pad? what usually gets covered with the denture?

Answer 7

back of the mandible

pear shaped pad gets covered

the retromolar pad doesn’t get covered

Question 8

where is the mylohyoid ridge?

Answer 8

the bony structure on the inside of the mandible

Question 9

which muscles affects the lingual sulcus?

Answer 9

mylohyoid muscle

Question 10

where does the lingual sulcus extend?

Answer 10

in the posterior of the mylohyoid ridge

Question 11

what are the 5 key anatomical features of the upper denture bearing area?

Answer 11

buccal sulcus
palate
vibrating line
palatine fovea
hamuler notch

Question 12

what is the vibration line?

Answer 12

the junction of the soft and hard palate

Question 13

what is the palatine fovea and hamular notch? where can these be found?

Answer 13

palatine fovea
- where the mucous glands insert

hamular notch
- the connective tissue between the pterygoid hamulus and maxillary tuberosity

Question 14

what is a frenum

Answer 14

a small piece of connective tissue that joins two structures

Question 15

what should be considered when recording an impression including the frenum?

Answer 15

the impression should record the space created when the frenum moves to all possible positions

Question 16

which anatomical features restricts the width of the upper posterior buccal sulci?

Answer 16

the coronoid process

Question 17

what is the functional depth determined by?

Answer 17

the anatomy and muscle movement

Question 18

what are the 4 different impression techniques?

Answer 18

muco-displasive
muco-static
differential pressure
functional

Question 19

describe muco-displasive impression technique, the advantages and disadvantages

Answer 19

• high pressure to compress the mucosa into a loaded position

pros
- claims good retention

cons
- likely resorption of alveolar bone

Question 20

when may you use a mucodisplasive technique?

Answer 20

in lower free end saddles

otherwise has been replaced by Altered Cast technique or differential pressure

Question 21

describe muco-static impression technique, the advantages and disadvantages

Answer 21

• attempt to record the mucosa in its rest position

pros
- comfort
- preserves underlying bone

cons
- lack of peripheral seal
- lack of retention
- only static if the mucosa doesn’t move - this is not truly a mucostatic impression

Question 22

describe the differential pressure impression technique

Answer 22

aims to be mucodisplasive in some areas are relatively mucostatic in others

Question 23

describe the functional impression technique, the advantages and disadvantages

Answer 23

• close mouth technique
• impression is taken under functioning dentures
• slow setting material, 2hrs-2days
• moulds the impression in function

pros
- denture bearing area is recorded in function
- gives better resultant contour

cons
- need pre-existing dentures
- hygiene issues when taking impression
- can’t select areas to load

Question 24

give an indication of functional impressions

Answer 24

to make a better impression of existing dentures

Question 25

what impressions are used for chrome dentures and for partial acrylic dentures? what type of impressions are they?

Answer 25

chrome dentures - silicone
partial acrylic - alginate

relative mucostatic impressions with low pressure

Question 26

what properties must the impression material uphold? describe each point.

Answer 26

1. viscosity
   - low for low pressure relative mucostatic imp
   - high enough to not gloop out of the tray
2. elasticity
   - emerge from undercut without tearing
3. dimensional stability
   - stay the same shape over time until its cast
4. hydrophilic
   - give surface detail
5. handling properties
   - mixing time, working time, setting time

Question 27

give the features of the impression trays

Answer 27

spaced tray - allow material to come out of undercut

unperforated perforations
- reduce pressures placed on teeth

stub handles

finger rests

trimmed for 2mm short of the functional depth