denture processing

Question 1

Which casts require relining?

Answer 1

• new dentures (lose adaptation
• old dentures (bone resorption)

Question 2

What is rebasing?

Answer 2

replacement of entire denture base with a new material

Question 3

relining and rebasing should be done without changing which relationship?

Answer 3

occlusal

Question 4

When is relining indicated?

Answer 4

when denture loses its adaptation to tissues due to bone resorption while other points (occlusion, aesthetics, occlusal vertical dimension and denture base material) are all satisfactory

Question 5

What is the procedure of relining of complete denture?

Answer 5

• remove the denture out of the patient’s mouth for 48 hours to give time for the mucosa to rest
• reduce the denture borders 2mm (to allow the flow of impression material to reach
  the depth of vestibule)
• remove undercuts from the fitting surface of the denture.
• take impression while the patient is closing in centric occlusion under closed mouth technique (to preserve occlusion)
• make boxing and pour the cast
• make flasking
• throw away the impression material to make space for new acrylic resin
• pack heat cured acrylic resin in the place of impression material
• curing (45° for 20 minutes) (long curing cycle)
• deflasking then laboratory remounting
• finishing and polishing

Question 6

If both upper and lower dentures need to be relined, which one is relined first and why?

Answer 6

lower denture as upper denture is supported by the palate but lower denture is not supported

Question 7

What to do if vertical dimensions are not correct?

Answer 7

remake

Question 8

What are the steps of rebasing?

Answer 8

• remove the denture out of the patient’s mouth for 48 hours to give time for the mucosa to rest
• reduce the denture borders 2mm and drilling 3 holes through the palate to allow the flow of impression material to reach the
  depth of vestibule
• remove undercuts from the fitting surface of the denture
• take impression while the patient is closing in centric occlusion under closed mouth technique to preserve occlusion (to preserve VDO)
• make boxing and pour the cast
• mount the cast and the denture on Hooper articulator or simple hinge articulator (to preserve occlusion and VDO)
• grind the denture base and throw it
• make new denture base from wax
• flasking → wax elimination → packing of acrylic resin → curing → deflasking →
  laboratory remounting → finishing and polishing

Question 9

When is rebasing done?

Answer 9

when denture contains cracks but occlusion must be right

Question 10

What does polishing of denture consist of?

Answer 10

making denture smooth and glossy without changing its contour

Question 11

When is finishing and polishing done?

Answer 11

after laboratory remounting (processing)

Question 12

What is the procedure of wax elimination?

Answer 12

placing flask in hot water

Question 13

What happens before wax elimination?

Answer 13

flasking

Question 14

What happens after wax elimination?

Answer 14

acrylic resin packing

Question 15

What happens after flasking is done?

Answer 15

wax is flushed out with hot water

Question 16

How is the cast remounted?

Answer 16

cast has indices or v-notches

Question 17

When is laboratory remounting done?

Answer 17

after processing and before finishing and polishing

Question 18

Who does the laboratory remounting?

Answer 18

lab technician

Question 19

Why do we remount the cast?

Answer 19

refining of occlusion

Question 20

What needs to be done if cusps are high in centric relation only?

Answer 20

deepen opposing fossa

Question 21

What needs to be done if cusps are high in centric and eccentric relations?

Answer 21

grinding working and non-working cusps

Question 22

What are the working sides of teeth of casts?

Answer 22

• BULL
• buccal upper
• lingual lower

Question 23

What is grinded in both sides?

Answer 23

non-functional cusps

Question 24

What should acrylic resin be glued to?

Answer 24

teeth

Question 25

What is the procedure of acrylic resin packing?

Answer 25

- put cellophane on cast before adding acrylic resin a- dd acrylic resin then close the flask and bench press - remove cellophane and excess - add cellophane again and close the flask, then open to remove excess, put cellophane then close the flask and bench press - repeat until no excess is left - cure in oven - cooling - deflasking

Question 26

In which stage is acrylic resin packing done?

Answer 26

dough stage

Question 27

Why is long cycle better than short cycle?

Answer 27

short cycle causes crazing

Question 28

Which cycle is better for curing: long or short?

Answer 28

long

Question 29

What are the ways of packing acrylic resin?

Answer 29

- injection method - open flask method (easier)

Question 30

What are the types of flasks?

Answer 30

- flask for upper cast - flask for lower cast

Question 31

What are the components of a flask?

Answer 31

- base (in the form of a cup) - middle part - top part (lid)

Question 32

What are the steps of flasking?

Answer 32

- place cast in lower part of flask and fill it up with stone until level of cast and then ass separating medium - place second part of flask and add stone but don't cover occlusal surface of teeth with stone then add separating medium again - add last layer of stone then close flask and it should touch occlusal surface of teeth - put flask in hot water and wax should melt - throw away trial denture base and add acrylic resin

Question 33

Why is the lower flask higher than upper?

Answer 33

presence of retromolar pad

Question 34

Do we add separating medium on occlusal surface of teeth?

Answer 34

no

Question 35

What is cap layer?

Answer 35

- last layer that covers occlusal surface - this makes sure teeth don't dislodge

Question 36

What happens before deflasking?

Answer 36

acrylic resin packing

Question 37

What happens after deflasking?

Answer 37

laboratory remounting

Question 38

What happens during deflasking?

Answer 38

flask cools to room temperature

Question 39

What is the objective of deflasking?

Answer 39

remove denture from investment material without breaking the denture or dislodging denture from cast for laboratory remounting

Question 40

What should the contour of the labial and buccal flange be and why?

Answer 40

- concave - help stabilisation of denture - adaptation of oral muscles - muscles are stronger than the denture

Question 41

What should the contour of the lingual flange be and why?

Answer 41

- convex then concave - convexity directly beneath the teeth - tongue may lie in this undercut and dislodge the lower denture - concavity away from teeth in the middle of the flange (not at any undercuts)

Question 42

Why should the palate be kept thin?

Answer 42

- pronunciation of "s" sound - it is the space between tongue and rugae area - tongue never touches the rugae area

Question 43

What is lisping?

Answer 43

- "th" sound replaces "s" sound - the the tongue is crowded against palate particularly on posterior region

Question 44

What are the causes of lisping?

Answer 44

- increase in thickness of acrylic at rugae area - backward arrangement of upper anterior teeth which leads to no space to pronounce "s"

Question 45

What is whistling?

Answer 45

"s" sound is pronounced too sharply

Question 46

What causes whistling?

Answer 46

- forward arrangement of upper anterior teeth - decrease thickness of acrylic in rugae area (insufficient waxing up) - low V.D.O. (short teeth and excessive freeway space)

Question 47

Why do we stipple gingiva?

Answer 47

to show rough appearance

Question 48

What should be contoured properly when contouring the root?

Answer 48

canine eminence